SchOS/kernel/dev/device.c

// The device model. See include/device.h for why it exists.
//
// A fixed table rather than a linked list: this is populated once during boot
// by whichever bus found each device, and read afterwards. Nothing is removed
// yet -- hot-unplug would need it, and when that arrives the in_use flag is
// already the hook for it.
//
// No lock. Every device_add() happens during single-threaded boot, before
// userspace exists, and every reader afterwards only walks. If a bus ever
// enumerates at runtime -- USB hotplug is the obvious one -- this needs a
// spinlock, and the reader in procfs needs to take it.

#include "types.h"
#include "defs.h"
#include "param.h"
#include "device.h"
#include "display.h"
#include "netdev.h"
#include "theme.h"
#include "text.h"
#include "spinlock.h"
#include "gfx.h"
#include "pci.h"
#include "mmu.h"
#include "memlayout.h"

static struct device devices[NDEVICE];
static int ndevices;

static const char *bus_names[DEVBUS_NBUS] = {
  [DEVBUS_PLATFORM] = "platform",
  [DEVBUS_PCI]      = "pci",
  [DEVBUS_USB]      = "usb",
};

static const char *class_names[DEVCLASS_NCLASS] = {
  [DEVCLASS_OTHER]   = "other",
  [DEVCLASS_DISPLAY] = "display",
  [DEVCLASS_INPUT]   = "input",
  [DEVCLASS_STORAGE] = "storage",
  [DEVCLASS_NET]     = "net",
  [DEVCLASS_BUS]     = "bus",
};

const char *
dev_bus_name(enum dev_bus b)
{
  if (b < 0 || b >= DEVBUS_NBUS || !bus_names[b])
    return "?";
  return bus_names[b];
}

const char *
dev_class_name(enum dev_class c)
{
  if (c < 0 || c >= DEVCLASS_NCLASS || !class_names[c])
    return "?";
  return class_names[c];
}

// How many devices already share this base name, so "vga" becomes vga0, vga1.
static int
count_base(const char *base)
{
  int n = 0;
  for (int i = 0; i < ndevices; i++) {
    const char *a = devices[i].name, *b = base;
    while (*b && *a == *b) { a++; b++; }
    // Matched the whole base and the rest is the index we appended.
    if (*b == '\0' && *a >= '0' && *a <= '9')
      n++;
  }
  return n;
}

struct device *
device_add(const char *base, enum dev_bus bus, enum dev_class class,
           const char *driver)
{
  if (ndevices >= NDEVICE)
    return 0;

  struct device *d = &devices[ndevices++];
  d->bus    = bus;
  d->class  = class;
  d->driver = driver;
  d->in_use = 1;

  int idx = count_base(base);
  int n = 0;
  while (base[n] && n < DEV_NAMELEN - 3) {
    d->name[n] = base[n];
    n++;
  }
  // Single digit is enough for NDEVICE of 32 per base name, and a two-digit
  // path that is never taken is a two-digit path that is never tested.
  if (idx > 9)
    idx = 9;
  d->name[n++] = (char)('0' + idx);
  d->name[n]   = '\0';

  return d;
}

void
device_set_desc(struct device *d, const char *s)
{
  if (!d)
    return;
  int n = 0;
  while (s[n] && n < (int)sizeof(d->desc) - 1) {
    d->desc[n] = s[n];
    n++;
  }
  d->desc[n] = '\0';
}

struct device *
device_at(int i)
{
  if (i < 0 || i >= ndevices)
    return 0;
  return &devices[i];
}

int
device_count(void)
{
  return ndevices;
}

struct device *
device_find_class(enum dev_class class)
{
  for (int i = 0; i < ndevices; i++)
    // Unclaimed devices are deliberately skipped. A display nobody drives is
    // not a display you can draw on, and returning it would push the "is there
    // a driver" check out to every caller.
    if (devices[i].class == class && devices[i].driver)
      return &devices[i];
  return 0;
}

// --- the display class -----------------------------------------------------
//
// Thin wrappers over device_find_class() plus a null check on each op. They
// exist so that consumers are not each written around a vtable that may be
// absent -- a compositor asking to present on a machine with no display driver
// should be a no-op, not a null dereference in the middle of a frame.

struct device *
display_get(void)
{
  return device_find_class(DEVCLASS_DISPLAY);
}

int
display_mode(struct display_mode *out)
{
  struct device *d = display_get();
  if (!d || !d->ops || !((struct display_ops *)d->ops)->mode)
    return -1;
  ((struct display_ops *)d->ops)->mode(d, out);
  return 0;
}

void *
display_acquire(uint32 *stride_out)
{
  struct device *d = display_get();
  if (!d || !d->ops || !((struct display_ops *)d->ops)->acquire)
    return 0;
  return ((struct display_ops *)d->ops)->acquire(d, stride_out);
}

void
display_present(int x, int y, int w, int h)
{
  struct device *d = display_get();
  if (!d || !d->ops || !((struct display_ops *)d->ops)->present)
    return;
  ((struct display_ops *)d->ops)->present(d, x, y, w, h);
}

// Where this display's pixels actually end up. 0 when the driver does not say,
// which callers must read as "assume it is the console's" -- see the comment
// on scanout_phys in include/display.h.
uint64
display_scanout_phys(void)
{
  struct device *d = display_get();
  if (!d || !d->ops || !((struct display_ops *)d->ops)->scanout_phys)
    return 0;
  return ((struct display_ops *)d->ops)->scanout_phys(d);
}

void
display_wait_vblank(void)
{
  struct device *d = display_get();
  if (!d || !d->ops || !((struct display_ops *)d->ops)->wait_vblank)
    return;
  ((struct display_ops *)d->ops)->wait_vblank(d);
}

// --- the crash screen, on every display the machine has ---------------------
//
// panic() paints the report into the console framebuffer, which is one screen
// on a machine that may have several. The others showed whatever they were
// showing when the machine died -- a shell prompt, most misleadingly -- and
// this is what walks them and puts the report there instead.
//
// Called from panic(), with interrupts off and everything the rules of that
// place imply: no allocation, no locks, no sleeping. It is deliberately the
// last thing the paint path does, so that a fault in here cannot cost the
// screen that was already drawn correctly.
//
// Two cases, and they are not the same:
//
//   the kernel still drives it   display_acquire() hands back a buffer; copy
//                                and present, the ordinary path
//   userspace drives it          the kernel let go of the device and the
//                                process holding it will not run again, so
//                                the driver it was taken from is asked to
//                                take it back for one frame
//
// The second is the one worth having. It is also the one that only works
// because the userspace driver said in advance where it was scanning out --
// see PCIIOC_PANICFB in include/pciuser.h.

// Copy the console framebuffer into a surface, with the same rules vgpud's
// mirror uses: the overlap, centred if the surface is larger, top-left if it
// is smaller. Both sides are XRGB8888; anything else is refused by whoever
// registered it.
// Copy rows [r0, r1] of the console framebuffer into a surface, with the same
// rules vgpud's mirror uses: the overlap, centred if the surface is larger,
// top-left if it is smaller. Both sides are XRGB8888; anything else is refused
// by whoever registered it. Returns the destination row span it wrote, so the
// caller can present exactly that.
static int
copy_console_rows(volatile uchar *dst, int dw, int dh, uint32 dstride,
                  int r0, int r1, int *out_y, int *out_h)
{
  const volatile uchar *src = gfx_fb_ptr();
  int sw = (int)gfx_width(), sh = (int)gfx_height();
  uint32 sstride = gfx_fb_stride();
  int cw = sw < dw ? sw : dw;
  int ch = sh < dh ? sh : dh;
  int x0 = (dw - cw) / 2, y0 = (dh - ch) / 2;

  if (!src || gfx_fb_bpp() != 32 || cw <= 0 || ch <= 0)
    return 0;
  if (r0 < 0) r0 = 0;
  if (r1 > ch - 1) r1 = ch - 1;
  if (r1 < r0)
    return 0;

  for (int y = r0; y <= r1; y++) {
    const volatile uint32 *s = (const volatile uint32 *)(src + (uint64)y * sstride);
    volatile uint32 *d = (volatile uint32 *)(dst + (uint64)(y0 + y) * dstride);
    for (int x = 0; x < cw; x++)
      d[x0 + x] = s[x];
  }
  *out_y = y0 + r0;
  *out_h = r1 - r0 + 1;
  return 1;
}

static void
panic_copy_console(volatile uchar *dst, int dw, int dh, uint32 dstride)
{
  int y, h;
  copy_console_rows(dst, dw, dh, dstride, 0, dh, &y, &h);
}

// --- the console, on a second screen ---------------------------------------
//
// A machine with two displays shows the console on one of them and whatever
// the other device happened to be left holding on the other -- which during
// boot is nothing at all: a black rectangle next to the machine starting up.
//
// So the rows the console draws are copied across as they are drawn. Cheap
// because gfx remembers which rows those were: a line of boot text is one
// cell-row transfer, not a screen.
//
// This is the same job vgpud does from userspace, and the two do not overlap.
// While the kernel drives the second GPU this runs; the moment vgpud claims
// it, display_acquire() returns nothing here and vgpud's mirror takes over
// from the same console framebuffer. The handover needs no coordination
// because neither side owns anything the other wants.
void
display_mirror_console(void)
{
  // cprintf() from inside the display driver would come straight back here
  // and present again, for ever.
  static int inside;
  // And two terminals on two CPUs would interleave into one command queue.
  // The lock is held across the copy and the present, which is microseconds of
  // polled virtio and the same thing the panic path does with everything else
  // already stopped.
  static struct spinlock lk;
  static int lk_init;
  // Which buffer was last brought up to date; see below.
  static volatile uchar *last_buf;
  struct display_mode m;
  uint32 stride = 0;
  volatile uchar *buf;
  int r0, r1, y, h;

  if (inside || !gfx_ready())
    return;

  // Is there a second screen at all? Asked first, and asked of the *scanout*,
  // because both halves of that matter.
  //
  // Of the scanout, because the buffer acquire() returns is not the same
  // thing: vga_fb hands back a back buffer it copies onto the console's own
  // framebuffer afterwards, so comparing pointers said "a different screen"
  // about the only screen there is -- and then mirrored the console onto
  // itself through two megabytes of intermediate.
  //
  // First, because this question has no side effects and acquire() has two:
  // it allocates a back buffer on first call, and it announces it with a
  // cprintf -- which comes straight back here. On a one-screen machine both
  // were pure waste, and the cprintf was a panic.
  uint64 phys = display_scanout_phys();
  if (phys == 0 || phys == gfx_fb_phys())
    return;

  if (!lk_init) {
    initlock(&lk, "dispmirror");
    lk_init = 1;
  }
  acquire(&lk);
  // Set before the first call into the driver, not after: a driver may
  // cprintf, cprintf comes back here, and the second entry would block on a
  // lock its own call chain is holding.
  inside = 1;
  buf = display_acquire(&stride);

  if (!buf || display_mode(&m) != 0 || m.bpp != 32) {
    inside = 0;
    release(&lk);
    return;
  }

  // A buffer we have not written before is owed the whole screen, not the
  // damage since last time.
  //
  // This is what a handover looks like from here: the loader draws the splash
  // straight into the framebuffer, the kernel's display driver probes some
  // milliseconds later with a black scanout of its own, and gfx has no damage
  // to report because gfx did not draw any of it. Without this the second head
  // went black at that moment and filled in a line at a time as output
  // arrived. It happens once per driver, and the same rule covers the device
  // coming back from a userspace driver that exited.
  int have = gfx_damage_take(&r0, &r1);
  if (buf != last_buf) {
    last_buf = buf;
    r0 = 0;
    r1 = (int)m.height - 1;
    have = 1;
  }
  if (!have) {
    inside = 0;
    release(&lk);
    return;
  }

  if (copy_console_rows(buf, m.width, m.height, stride ? stride : m.stride,
                        r0, r1, &y, &h))
    display_present(0, y, m.width, h);
  inside = 0;
  release(&lk);
}

void
display_panic_present(void)
{
  if (!gfx_ready())
    return;

  // The kernel's own display, when it is not the console's. On a machine where
  // the console is the VBE framebuffer and a virtio-gpu is the display class,
  // these are two different screens and only one of them has the report.
  {
    struct display_mode m;
    uint32 stride = 0;
    volatile uchar *buf = display_acquire(&stride);

    uint64 phys = display_scanout_phys();

    if (buf && phys && phys != gfx_fb_phys() &&
        display_mode(&m) == 0 && m.bpp == 32) {
      panic_copy_console(buf, m.width, m.height, stride ? stride : m.stride);
      display_present(0, 0, m.width, m.height);
    }
  }

  // And every display the kernel handed to a process. The report is painted
  // into memory that process registered, then its old kernel driver is asked
  // to put it on screen -- which means resetting the device out from under a
  // driver that is still nominally running. That is safe here and nowhere
  // else: nothing is going to run again.
  for (int i = 0; i < pci_count() && i < NPCI; i++) {
    const struct pci_driver *drv = 0;
    uint64 paddr = 0;
    uint32 stride = 0;
    int w = 0, h = 0;

    if (!pciuser_panic_surface(i, &paddr, &w, &h, &stride, &drv))
      continue;
    // A packed surface, because that is what the device is about to be told it
    // is. A padded one would shear, which is worse than not appearing.
    if (stride != (uint32)w * 4)
      continue;

    panic_copy_console((volatile uchar *)P2V(paddr), w, h, stride);
    drv->panic_present((struct pci_dev *)pci_get(i), paddr, w, h);
  }
}

// Drive the whole display path once and report what happened: find the class,
// read the mode, acquire a back buffer, draw into RAM, present it.
//
// A self-test rather than a unit test because none of this can be checked
// without a display: the assertion is "did the right pixels reach the screen",
// and the only instrument for that is a screendump. Triggered with
// `echo d > /proc/sysrq` and photographed by tools/dispshot.ps1.
//
// The pattern is chosen to be wrong in visible ways. Four solid quadrants in
// theme colours catch a stride error (the bands would slant) and a bpp error
// (the colours would be wrong); the white frame one pixel inside the edge
// catches an off-by-one in the present rectangle; and the fact that it is
// drawn entirely into RAM before a single byte reaches the framebuffer is what
// double buffering means.
void
display_selftest(void)
{
  struct display_mode m;
  uint32 stride;

  if (display_mode(&m) != 0) {
    cprintf("display: no display bound\n");
    return;
  }
  cprintf("display: %dx%d %dbpp stride %d\n", m.width, m.height, m.bpp, m.stride);

  unsigned char *b = display_acquire(&stride);
  if (!b) {
    cprintf("display: no back buffer available\n");
    return;
  }

  static const uint32 quad[4] = {
    SCH_ACCENT, SCH_ACCENT_DIM, SCH_DIM, SCH_BG
  };
  for (int y = 0; y < m.height; y++) {
    uint32 *row = (uint32 *)(b + (uint64)y * stride);
    int top = y < m.height / 2;
    for (int x = 0; x < m.width; x++) {
      int left = x < m.width / 2;
      row[x] = quad[(top ? 0 : 2) + (left ? 0 : 1)];
    }
  }
  for (int x = 1; x < m.width - 1; x++) {
    *(uint32 *)(b + 1 * (uint64)stride + x * 4) = SCH_FG;
    *(uint32 *)(b + (uint64)(m.height - 2) * stride + x * 4) = SCH_FG;
  }
  for (int y = 1; y < m.height - 1; y++) {
    *(uint32 *)(b + (uint64)y * stride + 1 * 4) = SCH_FG;
    *(uint32 *)(b + (uint64)y * stride + (m.width - 2) * 4) = SCH_FG;
  }

  // Between frames, so the blit does not land halfway down a scan-out.
  display_wait_vblank();
  display_present(0, 0, m.width, m.height);
  cprintf("display: presented a full frame\n");
}

// Draw a text specimen through the display class. `echo t > /proc/sysrq`.
//
// It exercises the three things a character-cell console cannot do, so a
// screenshot says whether the layer works rather than whether it compiled:
// glyphs on a common baseline at arbitrary x (not multiples of eight), text
// blended over an existing background rather than drawn into cleared cells, and
// codepoints above 255.
void
text_selftest(void)
{
  struct display_mode m;
  uint32 stride;

  if (display_mode(&m) != 0) {
    cprintf("text: no display\n");
    return;
  }
  unsigned char *b = display_acquire(&stride);
  if (!b) {
    cprintf("text: no back buffer\n");
    return;
  }

  struct surface s = { b, stride, m.width, m.height };
  struct font *f = font_builtin();

  // A background with structure in it, so blending is visible as blending
  // rather than as drawing onto a flat colour.
  for (int y = 0; y < m.height; y++) {
    uint32 *row = (uint32 *)(b + (uint64)y * stride);
    for (int x = 0; x < m.width; x++)
      row[x] = ((x / 32 + y / 32) & 1) ? SCH_BG : SCH_ACCENT_DIM;
  }

  int base = f->ops->baseline(f);
  int line = f->ops->height(f) + 6;
  int y = 80;

  text_draw(&s, f, 60, y + base, "SchOS text rendering", SCH_FG);
  y += line * 2;

  // Deliberately not on a multiple of eight. On the old console this string
  // could only start at x = 56 or x = 64.
  text_draw(&s, f, 61, y + base, "positioned at x=61, off the cell grid", SCH_DIM);
  y += line;
  text_draw(&s, f, 63, y + base, "and here at x=63", SCH_DIM);
  y += line * 2;

  // Above U+00FF, which a 256-entry table cannot index at all.
  text_draw(&s, f, 60, y + base,
            "utf-8: \xe2\x94\x8c\xe2\x94\x80\xe2\x94\x90 "
            "\xe2\x96\x88\xe2\x96\x93\xe2\x96\x92\xe2\x96\x91 "
            "\xc2\xb0 \xc2\xb1 \xe2\x86\x92 \xe2\x80\xa2", SCH_ACCENT);
  y += line * 2;

  // Measure, then centre on it -- the thing you cannot do without metrics.
  const char *msg = "measured and centred";
  int w = text_measure(f, msg);
  text_draw(&s, f, (m.width - w) / 2, y + base, msg, SCH_FG);

  display_present(0, 0, m.width, m.height);
  cprintf("text: drew a specimen, \"%s\" measures %d px\n", msg, w);
}

// ---------------------------------------------------------------------------
// The network class. See include/netdev.h.
//
// Plural where the display class is singular: a machine with two NICs is
// ordinary, and "the network" is not a thing a stack can ask for the way a
// compositor asks for "the display". So this walks, and the caller decides
// what to do with each interface it finds.

struct device *
netdev_at(int i)
{
  int seen = 0;

  for (int k = 0; k < device_count(); k++) {
    struct device *d = device_at(k);
    if (!d || d->class != DEVCLASS_NET || !d->driver || !d->ops)
      continue;
    if (seen++ == i)
      return d;
  }
  return 0;
}

int
netdev_count(void)
{
  int n = 0;

  while (netdev_at(n))
    n++;
  return n;
}

int
netdev_transmit(struct device *d, const void *frame, int len)
{
  if (!d || !d->ops || !((struct netdev_ops *)d->ops)->transmit)
    return -1;
  return ((struct netdev_ops *)d->ops)->transmit(d, frame, len);
}

int
netdev_receive(struct device *d, void *out, int cap)
{
  if (!d || !d->ops || !((struct netdev_ops *)d->ops)->receive)
    return 0;
  return ((struct netdev_ops *)d->ops)->receive(d, out, cap);
}

const unsigned char *
netdev_mac(struct device *d)
{
  if (!d || !d->ops || !((struct netdev_ops *)d->ops)->mac)
    return 0;
  return ((struct netdev_ops *)d->ops)->mac(d);
}

int
netdev_link_up(struct device *d)
{
  // A driver that cannot tell is treated as up. Reporting "down" for a link
  // whose state is simply unknown would stop the stack on hardware that works.
  if (!d || !d->ops || !((struct netdev_ops *)d->ops)->link_up)
    return 1;
  return ((struct netdev_ops *)d->ops)->link_up(d);
}

static void
put_be16(uint8 *p, uint16 v)
{
  p[0] = (uint8)(v >> 8);
  p[1] = (uint8)v;
}

// The ARP probe. Written for the e1000 when it was the only driver and there
// was no stack to test it with; it belongs here because it is the first thing
// anyone will want to run against the *next* driver, and none of it is
// specific to a chip.
//
// Under QEMU's user-mode networking the guest is 10.0.2.15 and the gateway is
// 10.0.2.2. SLIRP is silent until spoken to, which is why this has to transmit
// before it can expect to receive anything.
void
netdev_selftest(void)
{
  struct device *d = netdev_at(0);
  uint8 frame[42];
  uint8 reply[2048];

  if (!d) {
    cprintf("netdev: no interface\n");
    return;
  }

  const unsigned char *mac = netdev_mac(d);
  if (!mac) {
    cprintf("netdev: %s has no station address\n", d->name);
    return;
  }

  static const uint8 me[4]   = { 10, 0, 2, 15 };  // QEMU SLIRP guest address
  static const uint8 them[4] = { 10, 0, 2, 2 };   // and its gateway

  memset(frame, 0, sizeof(frame));
  for (int i = 0; i < 6; i++)
    frame[i] = 0xFF;                              // broadcast
  for (int i = 0; i < 6; i++)
    frame[6 + i] = mac[i];
  put_be16(&frame[12], 0x0806);                   // ARP

  put_be16(&frame[14], 1);                        // Ethernet
  put_be16(&frame[16], 0x0800);                   // IPv4
  frame[18] = 6;                                  // hardware address length
  frame[19] = 4;                                  // protocol address length
  put_be16(&frame[20], 1);                        // request
  for (int i = 0; i < 6; i++)
    frame[22 + i] = mac[i];                       // sender hardware address
  for (int i = 0; i < 4; i++)
    frame[28 + i] = me[i];                        // sender protocol address
  // target hardware address stays zero -- that is what is being asked
  for (int i = 0; i < 4; i++)
    frame[38 + i] = them[i];

  cprintf("netdev: %s asking who has %d.%d.%d.%d\n",
          d->name, them[0], them[1], them[2], them[3]);
  if (netdev_transmit(d, frame, sizeof(frame)) != 0) {
    cprintf("netdev: %s transmit ring full\n", d->name);
    return;
  }

  // Bounded poll. This runs from a sysrq write and there is nothing to sleep
  // on that would be woken by a raw frame, so spinning briefly is honest.
  //
  // It will also swallow whatever else is on the wire, including the stack's
  // own traffic if it is running -- which is why a non-ARP frame is reported
  // rather than treated as a failure.
  for (int spin = 0; spin < 20000000; spin++) {
    int n = netdev_receive(d, reply, sizeof(reply));
    if (n <= 0)
      continue;

    cprintf("netdev: %d bytes from %x:%x:%x:%x:%x:%x type %x\n",
            n, reply[6], reply[7], reply[8], reply[9], reply[10], reply[11],
            ((uint32)reply[12] << 8) | reply[13]);

    if (n >= 42 && reply[12] == 0x08 && reply[13] == 0x06 &&
        reply[20] == 0 && reply[21] == 2) {
      cprintf("netdev: ARP reply -- %d.%d.%d.%d is at %x:%x:%x:%x:%x:%x\n",
              reply[28], reply[29], reply[30], reply[31],
              reply[22], reply[23], reply[24], reply[25],
              reply[26], reply[27]);
      cprintf("netdev: %s self-test passed\n", d->name);
      return;
    }
  }
  cprintf("netdev: %s no reply\n", d->name);
}