8d836c66b2
PCI devices live at /sys/devices/pci0000:00/<addr> and USB devices under the xHCI controller that carries their bus, below that bus's root hub usbN; /sys/bus/pci/devices and /sys/bus/usb/devices are symlinks into it, and every device has its subsystem and driver links, which is how udev learns SUBSYSTEM and DRIVER. Writing to a device's uevent now announces it with MODALIAS, PCI_ID, PRODUCT and the rest, so udevadm trigger covers them, and the USB core sends add when a device is attached and remove as it goes. The root hub is announced when the controller comes up, before anything is plugged in. Checked under QEMU: lspci and udevadm info through the links, udevadm monitor showing the kernel and udev add event for device_add usb-kbd/usb-mouse and the remove event for device_del, and a triggered add for usb1 and 1-5. Known limits: the bus-to-controller mapping is a convention (bus N is the Nth xHCI in PCI order); PCI bridges are not parents; USB interfaces and /dev/bus/usb nodes are absent; busybox's lsusb reads /dev/bus/usb and prints nothing. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao
46 lines
1.8 KiB
C
46 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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//
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// The devices the kernel implements itself, as /sys and udev see them.
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//
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// /dev holds them already (kernel/fs/devfs.c). This is the other half of what
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// udev needs: for each node a place in /sys/devices, the class and dev/ links
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// that lead back to it, the facts udev's rules read (MAJOR, MINOR, DEVNAME,
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// input capabilities), and a way to announce it on the uevent netlink socket.
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#pragma once
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#include "core/types.h"
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#define KDEV_NAME 24
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#define KDEV_DEVNAME 32
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#define KDEV_BLK0 256 // kdev indexes from here are block devices
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enum { KD_NONE, KD_KEYBOARD, KD_MOUSE };
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struct kdev {
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char subsys[16]; // class: input, mem, tty, graphics, block
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char name[KDEV_NAME]; // directory name under the parent
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char devname[KDEV_DEVNAME]; // path below /dev, "" for a device with no node
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short major, minor;
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int block;
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int parent; // kdev index of the device it hangs off, or -1
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int cap; // KD_*: what an input device can do
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};
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int kdev_nsubsys(void);
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const char *kdev_subsys(int s);
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// Index of the Nth device that exists, 0.. until -1.
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int kdev_nth(int n);
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int kdev_get(int i, struct kdev *k);
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// The numbers stat() shows for its node, which are what /sys must show too.
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void kdev_numbers(const struct kdev *k, int *maj, int *min);
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// "devices/virtual/input/input0/event0": where it lives below /sys.
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int kdev_path(int i, char *buf, int cap);
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// Announce a device on the uevent socket: action is "add", "remove", "change".
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void kdev_uevent(int i, const char *action);
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// The next SEQNUM: events from every source (kdev, PCI, USB) share one count.
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uint kdev_seqnum(void);
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// What reading a device's `uevent` file says.
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int kdev_uevent_text(int i, char *buf, int cap);
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