4805dbd892
The fixed tables that a bigger machine than the one they were written
on reaches first, each raised to where it costs little:
NPCI 64 -> 256 a desktop with cards and Thunderbolt passes 64,
and the devices past it -- often the disk or
NIC last in bus order -- were ignored; 44 KB
NSOCK 32 -> 128 Unix sockets, which a desktop session uses by
the dozen; 4.9 KB each, 470 KB in all
NDEVICE 32 -> 128 120 bytes each
NIFDEV 16 -> 64 one dock is a hub, Ethernet, audio and a card
reader at two or three interfaces apiece
NETIF_MAX 4 -> 8
Device names took one digit and clamped there, so the tenth device of
a kind and every one after it was named "...9". Two digits now.
Checked under QEMU with two bridges of test devices: 68 functions,
all in lspci, /proc/pci and /sys/bus/pci.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
90 lines
3.5 KiB
C
90 lines
3.5 KiB
C
#pragma once
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// The device model: one list of everything attached, whatever bus found it.
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//
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// Before this there were two registries in kernel/drivers/registry.c -- one
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// array of PCI drivers, one of USB drivers -- and nothing that knew about both.
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// That is fine for binding drivers to hardware, which is all it was for, and
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// useless for the three things wanted next:
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//
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// *Enumeration.* "What is in this machine, and what claimed it" had no
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// answer that covered a USB disk and a PCI display at once. A device manager
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// is exactly that question, so it needs exactly this list.
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//
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// *Classes.* A compositor should ask for "the display" and not care whether
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// that is the VBE framebuffer or virtio-gpu. Without a class, every consumer
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// hardcodes a driver, and adding the second driver means editing the
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// consumers -- which is how a framebuffer address ends up hardcoded in three
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// places, as it once was here.
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//
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// *A boundary for drivers that are not compiled in.* Drivers the user
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// installs (see docs/architecture/devices.md) have to attach somewhere that is not "an
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// array in registry.c", because that array is fixed at link time.
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//
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// The shape is deliberately the one NeXTSTEP/macOS uses rather than Linux's:
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// a device is an object with a class and an ops vtable, and consumers talk to
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// the class. It is *not* a device tree -- there is no parent/child nesting
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// here, only a flat list with a bus tag, because nothing yet needs to walk a
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// hierarchy and a tree that nobody traverses is just a harder list.
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#define DEV_NAMELEN 24
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// Which bus found it. This is provenance, not capability -- what the device
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// *does* is its class.
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enum dev_bus {
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DEVBUS_PLATFORM = 0, // found by looking, not by enumerating: PS/2, VBE
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DEVBUS_PCI,
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DEVBUS_USB,
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DEVBUS_NBUS
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};
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// What it is. A consumer asks for a class and gets whatever is bound.
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enum dev_class {
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DEVCLASS_OTHER = 0,
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DEVCLASS_DISPLAY,
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DEVCLASS_INPUT,
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DEVCLASS_STORAGE,
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DEVCLASS_NET,
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DEVCLASS_BUS, // a controller that finds more devices (xHCI, hubs)
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DEVCLASS_AUDIO,
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DEVCLASS_NCLASS
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};
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struct device {
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char name[DEV_NAMELEN]; // "vga0", "xhci0" -- unique, human-readable
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char desc[48]; // free text for the enumerator
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enum dev_bus bus;
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enum dev_class class;
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// Where it came from, for the enumerator to print. Zero when not applicable.
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uint16 vendor, product;
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uint8 b, s, f; // PCI bus/slot/func
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const char *driver; // whatever claimed it, or 0 for unclaimed
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void *ops; // class-specific vtable; see display.h
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void *priv; // the driver's own state
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int in_use;
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};
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#define NDEVICE 128
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// Register a device. Returns it, or 0 if the table is full. The name is made
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// unique by appending an index, so a caller passes "vga" and gets "vga0".
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struct device *device_add(const char *base, enum dev_bus bus,
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enum dev_class class, const char *driver);
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// Set the human-readable description. Bounded copy into the fixed field, so
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// callers do not each need to know how long it is.
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void device_set_desc(struct device *, const char *);
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// Walk. Returns 0 past the end; index is dense over registered devices.
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struct device *device_at(int i);
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int device_count(void);
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// First device of a class with a bound driver, or 0. This is how a consumer
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// finds "the display" without naming a driver.
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struct device *device_find_class(enum dev_class class);
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const char *dev_bus_name(enum dev_bus);
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const char *dev_class_name(enum dev_class);
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