a4cfecd19c
"but Virtio GPU is still non functional. it only shows logo" -- and that was a fair reading of it. A second monitor showing a mark for ever is indistinguishable from a second monitor that does not work. The mark was the right answer to the question hybrid.md asked: H2 and H3 needed a screenshot that proved a *userspace process* had drawn something, and that the driver came back after being killed. Both are closed. What was left was a display whose entire output was a logo, on a machine whose console was sitting on the other head. So vgpud mirrors the console onto it. **A copy with a diff.** /dev/fb0 maps the console's framebuffer; the virtio backing store is already mapped, because vgpud allocated it. The backing therefore holds, at all times, exactly what was last sent to the device -- which means it *is* the previous frame, and "what changed" needs no third buffer. Ten times a second: compare rows, skip the ones that match, copy the ones that do not, transfer the one rectangle spanning the rows that changed. Hence present() becoming present_rect(). Moving one line of text through a full-screen transfer of a 1280x800 resource is most of a megabyte of copy for a few hundred bytes of difference, and this loop runs whether or not anything is happening. Mapping /dev/fb0 does not take the screen from the console: the pages are the ones the console draws into, and fb_mapped() only arranges a redraw when the fd is closed. This one never is. Sizes differ, so a head larger than the console centres it on the theme ground the mark already draws, and a smaller head shows the top-left corner -- which is where a terminal puts everything worth seeing. Scaling is the alternative and it is the wrong one; text resampled to a non-integer ratio is text you cannot read. The blocking accept() became poll() with the frame interval as its timeout, because holding the device is no longer the only thing to do. Not the endpoint: a compositor will want this head for itself, and when there is one this goes away. Until then the honest thing for a working display to show is the system that is running on it. **And a bug older than any of it.** schmode reported "cannot reach vgpud on /run/vgpud -- it is not running" about a process that was running perfectly well. Every boot after the first, on any image whose root is writable, and nothing to do with this change -- it reproduces on the previous commit, 3 runs in 4. bind() creates a node at the path, and /run is a directory on the root filesystem rather than a tmpfs. The node outlived the process that bound it and the boot it was bound in, so the next boot's vgpud claimed the device, drew, held it -- and then failed bind() on a name that already existed. A driver nobody could talk to, and an error message naming the wrong cause. It unlinks before binding now, which is what a Unix daemon does. The usual objection, that this lets a second instance steal a live socket, does not apply here: two vgpuds cannot coexist, because the first holds the PCI claim and the second is refused the device long before it reaches bind(). The claim is the mutual exclusion; the socket node never was. Verified by screendumping both heads over QMP: with the console at 1280x800 the two are byte-identical, and after `schmode 1024 768` the virtio head carries the console at the new mode. Three consecutive boots of one image all reach a working control socket, where the previous commit managed one. Both supported configurations: one boot each, no traps, no panics, socktest and memfdtest green. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
1144 lines
43 KiB
C
1144 lines
43 KiB
C
// SPDX-License-Identifier: Apache-2.0
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//
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// vgpud -- the virtio-gpu driver, outside the kernel.
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//
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// docs/plan/hybrid.md's first eviction. The same device the kernel drives in
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// kernel/drivers/gpu/virtio_gpu/, driven instead by a process that asks the
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// kernel for four things and nothing else:
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//
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// PCIIOC_CLAIM take the device (the kernel driver is asked to let go)
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// PCIIOC_CFG read config space, to find the vendor capabilities
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// mmap(BAR) reach the registers
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// PCIIOC_DMA memory the device can be pointed at
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//
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// The point is not that this is better than the in-kernel driver -- it is the
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// same code in a worse language for the job. The point is that it is a real
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// driver rather than a test program, so the interface has something to be
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// judged by, and what it asks for is what a foreign driver would ask for too.
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//
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// Note what is *not* here: no syscall knows this is a GPU. The kernel handed
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// over a PCI device and this decided it was a GPU, which is the property that
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// makes the interface general rather than a hole shaped like one thing.
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#include "types.h"
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#include "user.h"
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#include "fcntl.h"
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#include "posix.h"
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#include "pciuser.h"
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#include "virtio.h"
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#include "schinit.h"
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#include "socket.h"
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#include "theme.h" // SCH_BG, SCH_ACCENT -- one palette, see docs/branding
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#include "logo.h" // the mark, the same bytes the loader and console draw
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#include "fb.h" // the console framebuffer, which this mirrors
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// lib/glue.c has these -- they exist because the compiler emits calls to them
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// whether or not anything asks -- but include/user.h never declared them.
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void *memcpy(void *, const void *, unsigned long);
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int memcmp(const void *, const void *, unsigned long);
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// --- small output, since lib/ has no printf ---------------------------------
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// How the machine was booted. A driver coming up is progress on a boot you are
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// watching and noise on every other one; a driver *failing* is neither, and
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// stays on puts(). See kinfo() in kernel/core/console.c for the same rule one
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// level down.
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static int verbose_boot;
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static void
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read_bootmode(void)
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{
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char b[16];
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int fd = open("/proc/bootmode", O_RDONLY);
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int n;
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if (fd < 0)
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return;
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n = read(fd, b, sizeof(b) - 1);
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close(fd);
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if (n > 0) { b[n] = 0; verbose_boot = (b[0] == 'v'); }
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}
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static void
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puts(const char *s)
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{
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int n = 0;
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while (s[n]) n++;
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write(1, (void *)s, n);
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}
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// Progress, as opposed to news.
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static void
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vputs(const char *s)
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{
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if (verbose_boot)
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puts(s);
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}
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static void putn(long long v);
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static void
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vputn(long long v)
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{
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if (verbose_boot)
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putn(v);
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}
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static void
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putn(long long v)
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{
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char b[24];
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int i = 0;
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if (v < 0) { write(1, "-", 1); v = -v; }
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if (v == 0) { write(1, "0", 1); return; }
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while (v > 0) { b[i++] = '0' + (int)(v % 10); v /= 10; }
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while (i-- > 0) write(1, &b[i], 1);
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}
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static void
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puthex(unsigned long long v, int digits)
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{
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static const char h[] = "0123456789abcdef";
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char b[17];
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for (int i = digits - 1; i >= 0; i--) { b[i] = h[v & 0xF]; v >>= 4; }
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write(1, b, digits);
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}
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static void
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die(const char *why)
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{
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puts("vgpud: "); puts(why); puts("\n");
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exit();
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}
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// Not a failure: a report. There is no virtio-gpu here, or the kernel will not
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// give it up, and neither of those changes by trying again -- so this tells the
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// supervisor to stop, rather than being restarted every three seconds for the
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// rest of the uptime. See SCHINIT_EXIT_NORESTART in include/schinit.h.
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static void
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nothing_to_do(const char *why)
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{
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// Quiet on a quiet boot: "this machine has no virtio-gpu" is a fact about
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// the hardware and not a fault, and it is the same fact every time. It is
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// still an exit the supervisor is told about, which is what stops it being
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// restarted fifteen times in forty-five seconds.
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vputs("vgpud: "); vputs(why); vputs("\n");
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exit_group(SCHINIT_EXIT_NORESTART);
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}
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// --- register access --------------------------------------------------------
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static inline unsigned char r8 (volatile unsigned char *p, int o) { return p[o]; }
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static inline void w8 (volatile unsigned char *p, int o, unsigned char v) { p[o] = v; }
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static inline unsigned short r16(volatile unsigned char *p, int o) { return *(volatile unsigned short *)(p + o); }
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static inline void w16(volatile unsigned char *p, int o, unsigned short v) { *(volatile unsigned short *)(p + o) = v; }
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static inline unsigned int r32(volatile unsigned char *p, int o) { return *(volatile unsigned int *)(p + o); }
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static inline void w32(volatile unsigned char *p, int o, unsigned int v) { *(volatile unsigned int *)(p + o) = v; }
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static inline void w64(volatile unsigned char *p, int o, unsigned long long v)
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{
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// Two 32-bit writes, low half first. The virtio spec requires it and the
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// device latches on the high write; a single 64-bit store is a different
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// bus transaction and some implementations simply drop it.
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w32(p, o, (unsigned int)v);
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w32(p, o + 4, (unsigned int)(v >> 32));
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}
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// --- the device -------------------------------------------------------------
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static int pcifd;
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static int index_;
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static volatile unsigned char *common;
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static volatile unsigned char *notify;
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static volatile unsigned char *isr;
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static unsigned int notify_mult;
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static struct pciuser_info info;
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static unsigned int
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cfg32(unsigned int off)
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{
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struct pciuser_cfg c;
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c.index = (unsigned int)index_;
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c.offset = off & ~3u;
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c.value = 0;
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if (ioctl(pcifd, PCIIOC_CFG, &c) < 0)
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die("config read failed");
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return c.value;
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}
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static unsigned char
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cfg8(unsigned int off)
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{
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return (unsigned char)(cfg32(off) >> ((off & 3) * 8));
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}
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// Find a virtio configuration structure.
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//
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// A virtio 1.0 device does not put its registers at a fixed offset. It walks
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// you there: a vendor capability in config space names which BAR, and how far
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// into it, each structure lives. So a driver that cannot read config space
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// cannot find its own registers -- which is why PCIIOC_CFG exists, and why the
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// test program that came before this never needed it.
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static volatile unsigned char *
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find_cfg(int want, unsigned int *out_mult)
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{
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unsigned char off = cfg8(0x34) & 0xFC;
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while (off) {
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unsigned char id = cfg8(off);
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unsigned char next = cfg8(off + 1);
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if (id == PCI_CAP_ID_VNDR) {
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unsigned char type = cfg8(off + 3);
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unsigned char bar = cfg8(off + 4);
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unsigned int o = cfg32(off + 8);
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unsigned int len = cfg32(off + 12);
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if (type == want && bar < PCIUSER_MAXBAR && info.bar[bar].base) {
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if (out_mult)
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*out_mult = cfg32(off + 16);
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// Map from the start of the BAR, not from the capability's
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// offset: two capabilities usually live in one BAR, and
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// mapping each separately would hand out two mappings of
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// overlapping pages.
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unsigned long long want_len = (unsigned long long)o + len;
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if (want_len < 4096) want_len = 4096;
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if (want_len > info.bar[bar].size) want_len = info.bar[bar].size;
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volatile unsigned char *p =
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(volatile unsigned char *)mmap(0, want_len,
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PROT_READ | PROT_WRITE,
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MAP_SHARED, pcifd,
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info.bar[bar].base);
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if (p == 0 || (long)p == -1)
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return 0;
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return p + o;
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}
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}
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off = next & 0xFC;
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}
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return 0;
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}
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// --- the queue --------------------------------------------------------------
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#define CTRL_QUEUE 0
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static struct vring_desc *desc;
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static struct vring_avail *avail;
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static struct vring_used *used;
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static unsigned long long ring_phys;
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static unsigned short qsize, notify_off, last_used, next_desc;
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static void *cmdbuf, *respbuf;
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static unsigned long long cmdphys, respphys;
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static void
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queue_setup(void)
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{
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w16(common, VCOMMON_Q_SELECT, CTRL_QUEUE);
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qsize = r16(common, VCOMMON_Q_SIZE);
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if (qsize == 0)
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die("control queue has no slots");
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if (qsize > 64)
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qsize = 64; // more than one command in flight is not
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// something this driver has any use for
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w16(common, VCOMMON_Q_SIZE, qsize);
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notify_off = r16(common, VCOMMON_Q_NOTIFY_OFF);
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// One contiguous block for the three rings, laid out the way the spec
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// requires: descriptors, then available, then used, each aligned. The
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// device reads all three by physical address, so they have to come from
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// the kernel's DMA arena rather than from anything this process could
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// allocate for itself.
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unsigned int desc_sz = 16 * qsize;
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unsigned int avail_sz = 6 + 2 * qsize;
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struct pciuser_dma d;
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d.size = 16384;
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if (ioctl(pcifd, PCIIOC_DMA, &d) < 0)
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die("no DMA memory for the queue");
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unsigned long long base = d.uaddr;
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unsigned long long basep = d.paddr;
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unsigned int off_avail = (desc_sz + 1) & ~1u;
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unsigned int off_used = (off_avail + avail_sz + 3) & ~3u;
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desc = (struct vring_desc *)(base);
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avail = (struct vring_avail *)(base + off_avail);
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used = (struct vring_used *)(base + off_used);
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ring_phys = basep;
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for (unsigned int i = 0; i < 16384; i++)
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((volatile unsigned char *)base)[i] = 0;
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// Do not interrupt us. docmd() polls the used ring, so an interrupt is
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// not merely unwanted, it is dangerous: this process holds the device but
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// has no handler registered, and the line is shared with the e1000. A
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// level-triggered line nobody acknowledges re-fires for ever -- 77,000
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// times a second, which is what the first working run of this driver did
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// before this line existed. The storm detector in kernel/dev/irq.c named
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// the line and the neighbour it was drowning.
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avail->flags = VRING_AVAIL_F_NO_INTERRUPT;
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__sync_synchronize();
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w64(common, VCOMMON_Q_DESC, basep);
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w64(common, VCOMMON_Q_DRIVER, basep + off_avail);
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w64(common, VCOMMON_Q_DEVICE, basep + off_used);
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w16(common, VCOMMON_Q_ENABLE, 1);
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// Command and response buffers, also from the arena for the same reason.
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struct pciuser_dma b;
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b.size = 8192;
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if (ioctl(pcifd, PCIIOC_DMA, &b) < 0)
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die("no DMA memory for command buffers");
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cmdbuf = (void *)b.uaddr;
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cmdphys = b.paddr;
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respbuf = (void *)(b.uaddr + 4096);
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respphys = b.paddr + 4096;
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}
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// Submit one command and wait for the answer.
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//
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// Polled, not interrupt-driven. This driver issues a handful of commands at
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// startup and one flush per frame, and a poll on a used-ring index that the
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// device updates by DMA is both simpler and lower-latency than waking a
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// process. The interrupt path exists (PCIIOC_IRQ) and belongs in whatever
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// wants to sleep between frames.
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static int
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docmd(unsigned int cmdlen, unsigned int resplen)
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{
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unsigned short head = next_desc;
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desc[head].addr = cmdphys;
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desc[head].len = cmdlen;
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desc[head].flags = VRING_DESC_F_NEXT;
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desc[head].next = (unsigned short)(head + 1);
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desc[head + 1].addr = respphys;
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desc[head + 1].len = resplen;
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desc[head + 1].flags = VRING_DESC_F_WRITE;
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desc[head + 1].next = 0;
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avail->ring[avail->idx % qsize] = head;
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__sync_synchronize();
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avail->idx++;
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__sync_synchronize();
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*(volatile unsigned short *)(notify + notify_off * notify_mult) = CTRL_QUEUE;
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// Spin with a bound. A device that never answers is a bug somewhere, and
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// hanging for ever is a worse way to report it than saying so.
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for (int spin = 0; spin < 100000000; spin++) {
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__sync_synchronize();
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if (used->idx != last_used) {
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last_used = used->idx;
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next_desc = (unsigned short)((next_desc + 2) % qsize);
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return 0;
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}
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}
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return -1;
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}
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static void
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hdr_init(void *p, unsigned int type)
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{
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struct virtio_gpu_ctrl_hdr *h = (struct virtio_gpu_ctrl_hdr *)p;
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for (unsigned int i = 0; i < sizeof(*h); i++) ((unsigned char *)h)[i] = 0;
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h->type = type;
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}
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static int
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resp_ok(void)
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{
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struct virtio_gpu_ctrl_hdr *h = (struct virtio_gpu_ctrl_hdr *)respbuf;
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return h->type == VIRTIO_GPU_RESP_OK_NODATA ||
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h->type == VIRTIO_GPU_RESP_OK_DISPLAY_INFO;
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}
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// --- bringing the device up -------------------------------------------------
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static int width, height;
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static unsigned long long fb_uaddr, fb_paddr;
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static unsigned int fb_bytes; // what was allocated, not what is in use
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static int max_w, max_h; // the mode the allocation was sized for
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// The resource is recreated on every modeset; the framebuffer behind it is
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// not. PCIIOC_DMA has no free -- a driver's blocks come back when it exits and
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// not before -- so a modeset that allocated would exhaust sixteen slots and
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// then the arena, and the fault would look like a GPU bug rather than like
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// counting. Allocating once at the largest mode and reusing it for every
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// smaller one costs nothing: a 1024x768 frame is a prefix of a 1280x800 one.
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static unsigned int resource_id = 1;
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static void
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bring_up(void)
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{
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// Reset, then the status handshake in the order the spec sets out. A
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// device that finds the sequence wrong fails the feature step rather than
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// telling you which line was at fault, so it is written out plainly.
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w8(common, VCOMMON_STATUS, 0);
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while (r8(common, VCOMMON_STATUS) != 0)
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;
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w8(common, VCOMMON_STATUS, VSTATUS_ACK);
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w8(common, VCOMMON_STATUS, VSTATUS_ACK | VSTATUS_DRIVER);
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w32(common, VCOMMON_DFEAT_SEL, 1);
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unsigned int hi = r32(common, VCOMMON_DFEAT);
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if (!(hi & (1u << (VIRTIO_F_VERSION_1 - 32)))) {
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w8(common, VCOMMON_STATUS, VSTATUS_FAILED);
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die("device is not virtio 1.0");
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}
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w32(common, VCOMMON_GFEAT_SEL, 0);
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w32(common, VCOMMON_GFEAT, 0);
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w32(common, VCOMMON_GFEAT_SEL, 1);
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w32(common, VCOMMON_GFEAT, 1u << (VIRTIO_F_VERSION_1 - 32));
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w8(common, VCOMMON_STATUS, VSTATUS_ACK | VSTATUS_DRIVER | VSTATUS_FEATURES_OK);
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if (!(r8(common, VCOMMON_STATUS) & VSTATUS_FEATURES_OK)) {
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w8(common, VCOMMON_STATUS, VSTATUS_FAILED);
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die("device refused the feature set");
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}
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queue_setup();
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w8(common, VCOMMON_STATUS,
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VSTATUS_ACK | VSTATUS_DRIVER | VSTATUS_FEATURES_OK | VSTATUS_DRIVER_OK);
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// What size is the screen?
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hdr_init(cmdbuf, VIRTIO_GPU_CMD_GET_DISPLAY_INFO);
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if (docmd(sizeof(struct virtio_gpu_ctrl_hdr),
|
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sizeof(struct virtio_gpu_resp_display_info)) < 0)
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die("the device never answered GET_DISPLAY_INFO");
|
|
if (!resp_ok())
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die("GET_DISPLAY_INFO refused");
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|
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struct virtio_gpu_resp_display_info *di =
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(struct virtio_gpu_resp_display_info *)respbuf;
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|
width = (int)di->pmodes[0].r.width;
|
|
height = (int)di->pmodes[0].r.height;
|
|
if (width <= 0 || height <= 0)
|
|
die("the device reports no display");
|
|
|
|
vputs("vgpud: display is "); vputn(width); vputs("x"); vputn(height); vputs("\n");
|
|
|
|
// The framebuffer is claimed **before** the resource is created, because
|
|
// the resource has to be created at a size we can actually back.
|
|
//
|
|
// virtio-gpu's display size is the size of the host's window, which the
|
|
// user drags to whatever they like -- and every pixel of it is four bytes
|
|
// of contiguous DMA that has to be found twice during the handover, once
|
|
// for the kernel driver and once for this one. A big enough window does
|
|
// not fit, and what that used to look like was not a message, it was a
|
|
// loop:
|
|
//
|
|
// vgpud: wanted 7365 KB of DMA memory for a 1920x982 framebuffer
|
|
// schinitd: restarting os.schos.vgpud
|
|
// vgpud: wanted 7365 KB ... (and again, and again, until
|
|
// schinit: supervisor stopped answering schinit replaced schinitd)
|
|
//
|
|
// So: ask for what the display says, and if that cannot be had, ask for
|
|
// less. A smaller scanout on a larger display is a worse picture; a driver
|
|
// that will not start is no picture and a supervisor fighting itself.
|
|
{
|
|
struct pciuser_dma d;
|
|
int w = width, h = height, tries;
|
|
|
|
for (tries = 0; ; tries++) {
|
|
d.size = (unsigned long long)w * h * 4;
|
|
if (ioctl(pcifd, PCIIOC_DMA, &d) >= 0)
|
|
break;
|
|
|
|
// Two thirds each time, on an eight-pixel grid. Not halving:
|
|
// halving overshoots badly, and the arena is usually short by a
|
|
// little rather than by a lot.
|
|
w = ((w * 2 / 3) + 7) & ~7;
|
|
h = ((h * 2 / 3) + 7) & ~7;
|
|
if (w < 640 || h < 480) {
|
|
puts("vgpud: wanted "); putn(((long long)width * height * 4) / 1024);
|
|
puts(" KB of DMA memory for a "); putn(width); puts("x");
|
|
putn(height); puts(" framebuffer, and nothing down to 640x480\n");
|
|
puts("vgpud: `schdbg dma` shows the arena -- this is "
|
|
"DMA_ARENA_BYTES, not fragmentation\n");
|
|
// Not die(): a died driver is restarted, and restarting will
|
|
// fail identically for ever. The kernel keeps the VBE console,
|
|
// which is a working screen.
|
|
nothing_to_do("no room for a framebuffer; the console keeps the "
|
|
"VBE framebuffer");
|
|
}
|
|
}
|
|
|
|
if (tries) {
|
|
puts("vgpud: the display is "); putn(width); puts("x"); putn(height);
|
|
puts(" but only "); putn(w); puts("x"); putn(h);
|
|
puts(" of DMA could be had; using that\n");
|
|
width = w;
|
|
height = h;
|
|
}
|
|
fb_uaddr = d.uaddr;
|
|
fb_paddr = d.paddr;
|
|
}
|
|
fb_bytes = (unsigned int)(width * height * 4);
|
|
max_w = width;
|
|
max_h = height;
|
|
|
|
// A 2D resource the size of the screen.
|
|
struct virtio_gpu_resource_create_2d *c =
|
|
(struct virtio_gpu_resource_create_2d *)cmdbuf;
|
|
hdr_init(c, VIRTIO_GPU_CMD_RESOURCE_CREATE_2D);
|
|
c->resource_id = resource_id;
|
|
c->format = VIRTIO_GPU_FORMAT_B8G8R8X8_UNORM;
|
|
c->width = (unsigned int)width;
|
|
c->height = (unsigned int)height;
|
|
if (docmd(sizeof(*c), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 || !resp_ok())
|
|
die("RESOURCE_CREATE_2D refused");
|
|
|
|
// The framebuffer was claimed above, before the resource was created.
|
|
|
|
struct virtio_gpu_resource_attach_backing *a =
|
|
(struct virtio_gpu_resource_attach_backing *)cmdbuf;
|
|
hdr_init(a, VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING);
|
|
a->resource_id = resource_id;
|
|
a->nr_entries = 1;
|
|
// The entries follow the struct rather than being in it: the count is
|
|
// variable, so the command is a header with an array glued on the end.
|
|
struct virtio_gpu_mem_entry *e = (struct virtio_gpu_mem_entry *)(a + 1);
|
|
e->addr = fb_paddr;
|
|
e->length = fb_bytes;
|
|
e->padding = 0;
|
|
if (docmd(sizeof(*a) + sizeof(*e), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 ||
|
|
!resp_ok())
|
|
die("RESOURCE_ATTACH_BACKING refused");
|
|
|
|
// Put it on the screen.
|
|
struct virtio_gpu_set_scanout *so = (struct virtio_gpu_set_scanout *)cmdbuf;
|
|
hdr_init(so, VIRTIO_GPU_CMD_SET_SCANOUT);
|
|
so->r.x = so->r.y = 0;
|
|
so->r.width = (unsigned int)width;
|
|
so->r.height = (unsigned int)height;
|
|
so->scanout_id = 0;
|
|
so->resource_id = resource_id;
|
|
if (docmd(sizeof(*so), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 || !resp_ok())
|
|
die("SET_SCANOUT refused");
|
|
|
|
if (verbose_boot) {
|
|
puts("vgpud: scanout is ours, framebuffer at physical 0x");
|
|
puthex(fb_paddr, 16); puts("\n");
|
|
}
|
|
}
|
|
|
|
// Push what has been drawn to the host. Two commands, and both are needed:
|
|
// the transfer copies from the backing into the device's copy of the resource,
|
|
// the flush tells it to put that on screen.
|
|
//
|
|
// A rectangle rather than the screen, because the mirror below repaints a few
|
|
// changed rows at a time and a full-screen transfer of a 1280x800 resource to
|
|
// move one line of text is most of a megabyte for nothing. `offset` is where
|
|
// the rectangle's top-left pixel sits in the *backing*, which the device
|
|
// cannot work out for itself -- getting it wrong shifts the update diagonally
|
|
// rather than failing, so it is written once here and nowhere else.
|
|
static void
|
|
present_rect(int x, int y, int w, int h)
|
|
{
|
|
if (w <= 0 || h <= 0)
|
|
return;
|
|
|
|
struct virtio_gpu_transfer_to_host_2d *t =
|
|
(struct virtio_gpu_transfer_to_host_2d *)cmdbuf;
|
|
hdr_init(t, VIRTIO_GPU_CMD_TRANSFER_TO_HOST_2D);
|
|
t->r.x = (unsigned int)x;
|
|
t->r.y = (unsigned int)y;
|
|
t->r.width = (unsigned int)w;
|
|
t->r.height = (unsigned int)h;
|
|
t->offset = ((unsigned long long)y * (unsigned)width + x) * 4;
|
|
t->resource_id = resource_id;
|
|
t->padding = 0;
|
|
if (docmd(sizeof(*t), sizeof(struct virtio_gpu_ctrl_hdr)) < 0)
|
|
die("TRANSFER_TO_HOST_2D never answered");
|
|
|
|
struct virtio_gpu_resource_flush *f =
|
|
(struct virtio_gpu_resource_flush *)cmdbuf;
|
|
hdr_init(f, VIRTIO_GPU_CMD_RESOURCE_FLUSH);
|
|
f->r.x = (unsigned int)x;
|
|
f->r.y = (unsigned int)y;
|
|
f->r.width = (unsigned int)w;
|
|
f->r.height = (unsigned int)h;
|
|
f->resource_id = resource_id;
|
|
f->padding = 0;
|
|
if (docmd(sizeof(*f), sizeof(struct virtio_gpu_ctrl_hdr)) < 0)
|
|
die("RESOURCE_FLUSH never answered");
|
|
}
|
|
|
|
static void
|
|
present(void)
|
|
{
|
|
present_rect(0, 0, width, height);
|
|
}
|
|
|
|
// --- something to look at ---------------------------------------------------
|
|
|
|
// The mark, on the theme ground.
|
|
//
|
|
// This used to be a test card: three colour bands, four gradients, a
|
|
// checkerboard, and this instance's pid in binary along the bottom edge. That
|
|
// was scaffolding for hybrid.md's H2 and H3 -- a screenshot had to answer "did
|
|
// a *userspace process* put this here", and "did the driver come back" needed
|
|
// a second run to look different from a first that never stopped. Both
|
|
// milestones are closed, and what was left was a garish test pattern on a
|
|
// second display with no explanation of itself.
|
|
//
|
|
// The mark answers the same question a black screen cannot -- something is
|
|
// driving this device -- and answers it as the system rather than as a test
|
|
// rig. Same include/logo.h the loader splash and the kernel console draw, so
|
|
// there is one mark and one set of bytes.
|
|
static void
|
|
draw_mark(void)
|
|
{
|
|
volatile unsigned int *fb = (volatile unsigned int *)fb_uaddr;
|
|
int x0 = (width - LOGO_W) / 2;
|
|
int y0 = (height - LOGO_H) / 2;
|
|
|
|
for (int y = 0; y < height; y++)
|
|
for (int x = 0; x < width; x++)
|
|
fb[y * width + x] = SCH_BG;
|
|
|
|
if (x0 < 0 || y0 < 0)
|
|
return; // a display smaller than the mark: leave it
|
|
|
|
for (int dy = 0; dy < LOGO_H; dy++) {
|
|
for (int dx = 0; dx < LOGO_W; dx++) {
|
|
unsigned ink = LOGO_INK(dy * LOGO_W + dx);
|
|
if (!ink)
|
|
continue; // the mask is a square; the mark is not
|
|
// Coverage, not a stencil: the mark has soft edges, and stamping
|
|
// them as solid would show every one of them as a staircase.
|
|
unsigned r = (((SCH_ACCENT >> 16) & 0xFF) * ink +
|
|
((SCH_BG >> 16) & 0xFF) * (255 - ink)) / 255;
|
|
unsigned g = (((SCH_ACCENT >> 8) & 0xFF) * ink +
|
|
((SCH_BG >> 8) & 0xFF) * (255 - ink)) / 255;
|
|
unsigned b = (((SCH_ACCENT ) & 0xFF) * ink +
|
|
((SCH_BG ) & 0xFF) * (255 - ink)) / 255;
|
|
fb[(y0 + dy) * width + (x0 + dx)] = (r << 16) | (g << 8) | b;
|
|
}
|
|
}
|
|
}
|
|
|
|
// --- the mirror --------------------------------------------------------------
|
|
//
|
|
// What this display is *for*, which the mark alone never answered.
|
|
//
|
|
// The mark said "a userspace process is driving this device", which was the
|
|
// question H2 and H3 asked and is not a question any more. What was left was
|
|
// a second monitor showing a logo for ever, which is indistinguishable from a
|
|
// second monitor that does not work -- and that is exactly what it got called.
|
|
//
|
|
// So: the virtio-gpu head shows the console. Not because mirroring is the
|
|
// endpoint -- a compositor (Gate 3) will want this head for itself, and when
|
|
// there is one this goes away -- but because until then the honest thing for
|
|
// a working display to show is the system that is running on it.
|
|
//
|
|
// The mechanism is a *copy with a diff*, and the diff is what makes it cheap
|
|
// enough to run in a loop. The console framebuffer is mapped read-only-ish
|
|
// through /dev/fb0; the virtio backing store is already mapped. The backing
|
|
// therefore holds, at all times, exactly what was last sent to the device --
|
|
// which means it doubles as the previous frame, and no third buffer is needed
|
|
// to answer "what changed". Rows that compare equal are skipped; the run of
|
|
// rows that did not is copied and transferred as one rectangle.
|
|
//
|
|
// Mapping /dev/fb0 does not take the screen away from the console: the
|
|
// mapping is of the same physical pages the console draws into, and the
|
|
// kernel's fb_mapped() only arranges for a redraw when the fd is *closed*.
|
|
// This one is never closed.
|
|
// Ten passes a second. Fast enough that typing does not feel posted from
|
|
// elsewhere, slow enough that the comparison -- a few megabytes of memcmp
|
|
// against rows that are usually identical -- is not what the machine spends
|
|
// its time on.
|
|
#define MIRROR_MS 100
|
|
#define MIRROR_TICKS 10 // the same interval, in sleep()'s units
|
|
|
|
static volatile unsigned char *con_fb; // the console's framebuffer
|
|
static unsigned con_w, con_h, con_stride;
|
|
static int mirror_x, mirror_y, mirror_w, mirror_h;
|
|
static int mirror_full; // next pass copies every row
|
|
|
|
// Where the console lands on this display. The two are not the same size --
|
|
// the console is whatever mode the firmware left, this head is whatever mode
|
|
// it was last told -- so the smaller of each dimension is what gets copied.
|
|
//
|
|
// A head larger than the console centres it, on the theme ground draw_mark()
|
|
// leaves behind. A head smaller than the console shows its top-left corner,
|
|
// which is not a compromise: a terminal fills from the top-left, so that is
|
|
// where everything worth seeing is. Scaling is the alternative and it is the
|
|
// wrong one -- text resampled to a non-integer ratio is text you cannot read.
|
|
//
|
|
// Called again after every modeset, because both halves of that arithmetic
|
|
// move.
|
|
static void
|
|
mirror_geometry(void)
|
|
{
|
|
mirror_w = (int)con_w < width ? (int)con_w : width;
|
|
mirror_h = (int)con_h < height ? (int)con_h : height;
|
|
mirror_x = (width - mirror_w) / 2;
|
|
mirror_y = (height - mirror_h) / 2;
|
|
mirror_full = 1;
|
|
}
|
|
|
|
// Returns 0 if there is a console to mirror. Every failure here is a reason to
|
|
// keep showing the mark rather than a reason to die: a machine with no
|
|
// framebuffer console is a machine this daemon still has to hold the device
|
|
// on.
|
|
static int
|
|
mirror_open(void)
|
|
{
|
|
struct fb_var_screeninfo var;
|
|
struct fb_fix_screeninfo fix;
|
|
unsigned char *p;
|
|
|
|
int fd = open("/dev/fb0", O_RDWR);
|
|
if (fd < 0)
|
|
return -1;
|
|
if (ioctl(fd, FBIOGET_VSCREENINFO, &var) < 0 ||
|
|
ioctl(fd, FBIOGET_FSCREENINFO, &fix) < 0) {
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
|
|
// The copy below is a run of 32-bit words, so the two formats have to
|
|
// agree exactly rather than approximately. They do today -- both sides are
|
|
// XRGB8888 -- and if a console ever comes up 16-bit or BGR, converting per
|
|
// pixel is a different function and this one should decline instead of
|
|
// painting the screen in the wrong colours.
|
|
if (var.bits_per_pixel != 32 || var.red.offset != 16 ||
|
|
var.green.offset != 8 || var.blue.offset != 0) {
|
|
vputs("vgpud: console is not XRGB8888; not mirroring it\n");
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
|
|
p = mmap(0, fix.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
|
|
if (p == 0 || (long)p < 0) {
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
|
|
con_fb = p;
|
|
con_w = var.xres;
|
|
con_h = var.yres;
|
|
con_stride = fix.line_length; // NOT xres*4; the card may pad each row
|
|
mirror_geometry();
|
|
return 0; // fd deliberately left open; see above
|
|
}
|
|
|
|
// One pass. Cheap when nothing changed, which is almost always.
|
|
static void
|
|
mirror_pass(void)
|
|
{
|
|
volatile unsigned int *dst;
|
|
int y, first = -1, last = -1;
|
|
unsigned rowbytes;
|
|
|
|
if (!con_fb)
|
|
return;
|
|
|
|
dst = (volatile unsigned int *)fb_uaddr;
|
|
rowbytes = (unsigned)mirror_w * 4;
|
|
|
|
for (y = 0; y < mirror_h; y++) {
|
|
const void *src = (const void *)(con_fb +
|
|
(unsigned long)y * con_stride);
|
|
void *row = (void *)&dst[(unsigned long)(mirror_y + y) * width +
|
|
mirror_x];
|
|
if (!mirror_full && memcmp(row, src, rowbytes) == 0)
|
|
continue;
|
|
memcpy(row, src, rowbytes);
|
|
if (first < 0)
|
|
first = y;
|
|
last = y;
|
|
}
|
|
mirror_full = 0;
|
|
|
|
// One rectangle covering every changed row, rather than one per run. Text
|
|
// scrolling dirties everything anyway, and a cursor blinking at the bottom
|
|
// of a full screen is the worst case -- two rows apart, one transfer of
|
|
// the span between them. Chasing that with a list of runs is more code
|
|
// than the copy it saves.
|
|
if (first >= 0)
|
|
present_rect(mirror_x, mirror_y + first, mirror_w, last - first + 1);
|
|
}
|
|
|
|
// --- the modeset --------------------------------------------------------------
|
|
//
|
|
// docs/plan/hybrid.md milestone H3: *"a modeset API, which is the thing an
|
|
// out-of-kernel GPU driver makes affordable and an in-kernel one never got."*
|
|
//
|
|
// The claim is worth testing rather than repeating, so here is the whole of
|
|
// it: five commands to the device, no kernel change, and a driver that can be
|
|
// killed and restarted if it goes wrong. In the kernel the same sequence would
|
|
// be five commands *and* a reason to be nervous, because getting it wrong
|
|
// takes the machine rather than one process -- which is precisely why the
|
|
// in-kernel driver never grew one.
|
|
static int
|
|
set_mode(int w, int h)
|
|
{
|
|
if (w <= 0 || h <= 0)
|
|
return -1;
|
|
// Bounded by the allocation, not by the device. See fb_bytes.
|
|
if ((unsigned int)(w * h * 4) > fb_bytes)
|
|
return -2;
|
|
|
|
// Let go of the old resource first. The backing pages are ours and survive
|
|
// this; only the device's view of them goes away.
|
|
struct virtio_gpu_resource_unref *u =
|
|
(struct virtio_gpu_resource_unref *)cmdbuf;
|
|
hdr_init(u, VIRTIO_GPU_CMD_RESOURCE_UNREF);
|
|
u->resource_id = resource_id;
|
|
u->padding = 0;
|
|
if (docmd(sizeof(*u), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 || !resp_ok())
|
|
return -3;
|
|
|
|
// A fresh id rather than the same one again: the spec does not promise the
|
|
// old id is reusable the instant the unref completes, and an id is free.
|
|
resource_id++;
|
|
|
|
struct virtio_gpu_resource_create_2d *c =
|
|
(struct virtio_gpu_resource_create_2d *)cmdbuf;
|
|
hdr_init(c, VIRTIO_GPU_CMD_RESOURCE_CREATE_2D);
|
|
c->resource_id = resource_id;
|
|
c->format = VIRTIO_GPU_FORMAT_B8G8R8X8_UNORM;
|
|
c->width = (unsigned int)w;
|
|
c->height = (unsigned int)h;
|
|
if (docmd(sizeof(*c), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 || !resp_ok())
|
|
return -4;
|
|
|
|
struct virtio_gpu_resource_attach_backing *a =
|
|
(struct virtio_gpu_resource_attach_backing *)cmdbuf;
|
|
hdr_init(a, VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING);
|
|
a->resource_id = resource_id;
|
|
a->nr_entries = 1;
|
|
struct virtio_gpu_mem_entry *e = (struct virtio_gpu_mem_entry *)(a + 1);
|
|
e->addr = fb_paddr;
|
|
e->length = (unsigned int)(w * h * 4);
|
|
e->padding = 0;
|
|
if (docmd(sizeof(*a) + sizeof(*e), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 ||
|
|
!resp_ok())
|
|
return -5;
|
|
|
|
struct virtio_gpu_set_scanout *so = (struct virtio_gpu_set_scanout *)cmdbuf;
|
|
hdr_init(so, VIRTIO_GPU_CMD_SET_SCANOUT);
|
|
so->r.x = so->r.y = 0;
|
|
so->r.width = (unsigned int)w;
|
|
so->r.height = (unsigned int)h;
|
|
so->scanout_id = 0;
|
|
so->resource_id = resource_id;
|
|
if (docmd(sizeof(*so), sizeof(struct virtio_gpu_ctrl_hdr)) < 0 || !resp_ok())
|
|
return -6;
|
|
|
|
width = w;
|
|
height = h;
|
|
return 0;
|
|
}
|
|
|
|
// --- the control socket -------------------------------------------------------
|
|
//
|
|
// Lines of text, the same choice and the same reasons as
|
|
// docs/architecture/debugging.md's: it can be driven by hand, it needs no
|
|
// client to be useful, and a garbled answer is still mostly readable.
|
|
//
|
|
// The name is a *name*, not a path. AF_UNIX sockets in this kernel live in a
|
|
// table keyed by string and never touch the filesystem -- that is item 3 of
|
|
// docs/plan/foundations.md and it is not built. Nothing here depends on which
|
|
// it is, and the day it becomes a real path this keeps working.
|
|
#define VGPUD_SOCKET "/run/vgpud"
|
|
|
|
static void
|
|
reply(int fd, const char *s)
|
|
{
|
|
int n = 0;
|
|
while (s[n]) n++;
|
|
write(fd, (void *)s, n);
|
|
}
|
|
|
|
static void
|
|
reply_dim(int fd, int w, int h, const char *tail)
|
|
{
|
|
char b[48];
|
|
int n = 0, i, v;
|
|
|
|
v = w; i = 0; { char t[12]; if (!v) t[i++]='0'; while (v) { t[i++]='0'+v%10; v/=10; }
|
|
while (i-- > 0) b[n++] = t[i]; }
|
|
b[n++] = 'x';
|
|
v = h; i = 0; { char t[12]; if (!v) t[i++]='0'; while (v) { t[i++]='0'+v%10; v/=10; }
|
|
while (i-- > 0) b[n++] = t[i]; }
|
|
b[n] = 0;
|
|
reply(fd, b);
|
|
reply(fd, tail);
|
|
}
|
|
|
|
static int
|
|
num(const char **sp)
|
|
{
|
|
const char *s = *sp;
|
|
int v = 0, any = 0;
|
|
while (*s == ' ' || *s == 'x' || *s == '\t') s++;
|
|
while (*s >= '0' && *s <= '9') { v = v * 10 + (*s++ - '0'); any = 1; }
|
|
*sp = s;
|
|
return any ? v : -1;
|
|
}
|
|
|
|
// The modes offered. Not a list the device publishes -- virtio-gpu has no mode
|
|
// table, it will scan out whatever size it is given -- so this is the set that
|
|
// fits the framebuffer, which is the only real constraint.
|
|
static const struct { int w, h; } offered[] = {
|
|
{ 1280, 800 }, { 1280, 720 }, { 1024, 768 }, { 800, 600 }, { 640, 480 },
|
|
};
|
|
#define NOFFERED ((int)(sizeof(offered) / sizeof(offered[0])))
|
|
|
|
static void
|
|
serve(int fd)
|
|
{
|
|
char line[128];
|
|
int n;
|
|
|
|
while ((n = read(fd, line, sizeof(line) - 1)) > 0) {
|
|
const char *p = line;
|
|
line[n] = 0;
|
|
|
|
while (*p == ' ') p++;
|
|
|
|
if (p[0] == 'i') { /* info */
|
|
reply_dim(fd, width, height, " current\n");
|
|
reply_dim(fd, max_w, max_h, " maximum, framebuffer ");
|
|
{
|
|
char b[16]; int i = 0, v = (int)(fb_bytes / 1024);
|
|
char t[12]; int j = 0;
|
|
if (!v) t[j++] = '0';
|
|
while (v) { t[j++] = '0' + v % 10; v /= 10; }
|
|
while (j-- > 0) b[i++] = t[j];
|
|
b[i] = 0;
|
|
reply(fd, b);
|
|
}
|
|
reply(fd, " KB\n");
|
|
} else if (p[0] == 'm' && p[1] == 'o' && p[2] == 'd' && p[3] == 'e' &&
|
|
p[4] == 's') { /* modes */
|
|
for (int i = 0; i < NOFFERED; i++) {
|
|
if ((unsigned int)(offered[i].w * offered[i].h * 4) > fb_bytes)
|
|
continue;
|
|
reply_dim(fd, offered[i].w, offered[i].h,
|
|
(offered[i].w == width && offered[i].h == height)
|
|
? " *\n" : "\n");
|
|
}
|
|
} else if (p[0] == 'm') { /* mode W H or mode WxH */
|
|
int w, h;
|
|
while (*p && *p != ' ') p++;
|
|
w = num(&p);
|
|
h = num(&p);
|
|
if (w < 0 || h < 0) {
|
|
reply(fd, "usage: mode <width> <height>\n");
|
|
} else {
|
|
int r = set_mode(w, h);
|
|
if (r == -2) {
|
|
reply(fd, "refused: larger than the framebuffer, which is "
|
|
"fixed at startup\n");
|
|
} else if (r < 0) {
|
|
reply(fd, "the device refused the modeset\n");
|
|
} else {
|
|
// The ground first, then the console re-laid onto it: the
|
|
// mirror's placement is derived from both sizes, and one
|
|
// of them just changed.
|
|
draw_mark();
|
|
mirror_geometry();
|
|
mirror_pass();
|
|
present();
|
|
reply_dim(fd, width, height, " ok\n");
|
|
puts("vgpud: mode is now "); putn(width); puts("x");
|
|
putn(height); puts("\n");
|
|
}
|
|
}
|
|
} else if (p[0] == 'q') { /* quit */
|
|
return;
|
|
} else {
|
|
reply(fd, "info | modes | mode <w> <h> | quit\n");
|
|
}
|
|
}
|
|
}
|
|
|
|
static int
|
|
control_socket(void)
|
|
{
|
|
struct sockaddr_un sa;
|
|
int fd, i;
|
|
|
|
fd = socket(AF_UNIX, SOCK_STREAM, 0);
|
|
if (fd < 0)
|
|
return -1;
|
|
|
|
for (i = 0; i < (int)sizeof(sa.sun_path); i++)
|
|
sa.sun_path[i] = 0;
|
|
sa.sun_family = AF_UNIX;
|
|
for (i = 0; VGPUD_SOCKET[i] && i < (int)sizeof(sa.sun_path) - 1; i++)
|
|
sa.sun_path[i] = VGPUD_SOCKET[i];
|
|
|
|
// The node from the last time this ran, if there is one.
|
|
//
|
|
// /run is a directory on the root filesystem rather than a tmpfs, so a
|
|
// socket node outlives the process that bound it *and* the boot it was
|
|
// bound in. bind() onto an existing name fails, and what that produced was
|
|
// a vgpud holding the device with no way to talk to it -- on every boot
|
|
// after the first, on any image whose root is writable. `schmode` said
|
|
// "it is not running" about a process that was running perfectly well.
|
|
//
|
|
// Unlinking first is what a Unix daemon does, and the usual objection --
|
|
// that it lets a second instance steal a live socket -- does not apply
|
|
// here: two vgpuds cannot coexist anyway, because the first holds the PCI
|
|
// claim and the second is refused the device long before it reaches this
|
|
// function. The claim is the mutual exclusion; this node never was.
|
|
unlink(VGPUD_SOCKET);
|
|
|
|
if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
if (listen(fd, 4) < 0) {
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
return fd;
|
|
}
|
|
|
|
// --- main -------------------------------------------------------------------
|
|
|
|
int
|
|
main(int argc, char *argv[])
|
|
{
|
|
read_bootmode();
|
|
|
|
pcifd = open("/dev/pci", O_RDWR);
|
|
if (pcifd < 0)
|
|
die("cannot open /dev/pci");
|
|
|
|
int count = 0;
|
|
if (ioctl(pcifd, PCIIOC_COUNT, &count) < 0)
|
|
die("PCIIOC_COUNT failed");
|
|
|
|
// Find it by what it is, not by where it is. A driver that takes a bus
|
|
// address on the command line is one nobody can start automatically.
|
|
index_ = -1;
|
|
for (int i = 0; i < count; i++) {
|
|
info.index = (unsigned int)i;
|
|
if (ioctl(pcifd, PCIIOC_INFO, &info) < 0)
|
|
continue;
|
|
if (info.vendor == VIRTIO_VENDOR && info.device == VIRTIO_DEV_GPU) {
|
|
index_ = i;
|
|
break;
|
|
}
|
|
}
|
|
if (index_ < 0)
|
|
nothing_to_do("no virtio-gpu on this machine");
|
|
|
|
if (verbose_boot) {
|
|
puts("vgpud: virtio-gpu at "); puthex(info.bus, 2); puts(":");
|
|
puthex(info.slot, 2); puts("."); puthex(info.func, 1);
|
|
if (info.driver[0]) { puts(", currently held by "); puts(info.driver); }
|
|
puts("\n");
|
|
}
|
|
|
|
// The kernel driver is asked to let go here. It puts the VBE framebuffer
|
|
// back on screen before returning, so there is never a moment with no
|
|
// display -- see vgpu_release() and vga_fb_restore().
|
|
if (ioctl(pcifd, PCIIOC_CLAIM, &index_) < 0)
|
|
nothing_to_do("claim refused -- the kernel driver would not release it");
|
|
vputs("vgpud: claimed\n");
|
|
|
|
// The info is re-read because claiming is what enables memory space and
|
|
// bus mastering, and a BAR read before that can legitimately be zero.
|
|
info.index = (unsigned int)index_;
|
|
if (ioctl(pcifd, PCIIOC_INFO, &info) < 0)
|
|
die("PCIIOC_INFO failed after claim");
|
|
|
|
common = find_cfg(VIRTIO_PCI_CAP_COMMON_CFG, 0);
|
|
notify = find_cfg(VIRTIO_PCI_CAP_NOTIFY_CFG, ¬ify_mult);
|
|
isr = find_cfg(VIRTIO_PCI_CAP_ISR_CFG, 0);
|
|
if (!common || !notify)
|
|
die("no modern virtio capabilities -- not a 1.0 device");
|
|
|
|
bring_up();
|
|
draw_mark();
|
|
present();
|
|
|
|
vputs("vgpud: pid ");
|
|
vputn(getpid());
|
|
vputs(" drew the mark from userspace\n");
|
|
|
|
// From here the head shows the console rather than the mark. The mark
|
|
// stays on screen if there is nothing to mirror, and stays as the ground
|
|
// around the console either way.
|
|
if (mirror_open() == 0) {
|
|
mirror_pass();
|
|
vputs("vgpud: mirroring the console\n");
|
|
}
|
|
|
|
if (argc > 1 && argv[1][0] == '-' && argv[1][1] == 'x') {
|
|
// Exit without releasing, to show what a crashed driver leaves behind:
|
|
// the kernel takes the device back and the screen is whatever the
|
|
// device was last told to scan out.
|
|
puts("vgpud: exiting without cleaning up (simulated crash)\n");
|
|
exit();
|
|
}
|
|
|
|
// Hold the device, and answer.
|
|
//
|
|
// This used to sleep for ever, with a comment arguing that building a
|
|
// control socket before there is a compositor to judge it is the mistake
|
|
// the plan warns about. That argument was right about a *compositor*
|
|
// protocol and wrong as a reason to have no socket at all: H3 is a modeset
|
|
// API, and a modeset has a consumer that exists -- somebody changing the
|
|
// mode and looking at the screen. `schmode` is that consumer, and it is
|
|
// enough to judge an interface this small.
|
|
//
|
|
// What is deliberately *not* here is anything a compositor would need:
|
|
// no buffer submission, no damage, no vblank. Those wait for a compositor,
|
|
// for the original reason.
|
|
//
|
|
// Blocking accept, one client at a time. A driver whose whole job is to
|
|
// hold a device has nothing else to be doing, and a poll loop would be
|
|
// machinery in place of a call.
|
|
//
|
|
// Being killed here is not an error path, it is the H2 path: schinit
|
|
// restarts this process, and the device has to come back with it.
|
|
int srv = control_socket();
|
|
if (srv < 0) {
|
|
vputs("vgpud: no control socket; the mode is fixed at "
|
|
"whatever the device reported\n");
|
|
for (;;) {
|
|
sleep(MIRROR_TICKS);
|
|
mirror_pass();
|
|
}
|
|
}
|
|
|
|
vputs("vgpud: listening on " VGPUD_SOCKET "\n");
|
|
|
|
// Not a blocking accept any more. That was right when holding the device
|
|
// was the whole job; now there is a second thing to do between calls, and
|
|
// poll() is how a process waits for one of two reasons to wake up. The
|
|
// timeout is the frame interval: with nothing happening, this wakes ten
|
|
// times a second, compares rows, finds none changed, and goes back to
|
|
// sleep.
|
|
struct pollfd pf;
|
|
pf.fd = srv;
|
|
pf.events = POLLIN;
|
|
for (;;) {
|
|
pf.revents = 0;
|
|
if (poll(&pf, 1, MIRROR_MS) > 0 && (pf.revents & POLLIN)) {
|
|
int c = accept(srv, 0, 0);
|
|
if (c >= 0) {
|
|
serve(c);
|
|
close(c);
|
|
}
|
|
}
|
|
mirror_pass();
|
|
}
|
|
}
|