CVS commit: src/sys/dev/usb

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Sun Nov 29 22:54:51 UTC 2020

Modified Files:
        src/sys/dev/usb: uhid.c uhidev.c uhidev.h

Log Message:
usb: Overhaul uhid(4) and uhidev(4) locking.

- uhidev API rules:

  1. Call uhidev_open when you want exclusive use of a report id.
     After it succeeds, you will get interrupts.

  2. Call uhidev_close when done with exclusive use of a report id.
     After it returns, you will no longer get interrupts.

     => uhidev_open/close do not nest.

  3. uhidev_write no longer requires the caller to have exclusive
     access -- if there is a write in progress, it will block
     interruptibly until done.  This way drivers for individual
     report ids need not work separately to coordinate their writes.

  4. You must uhidev_stop to abort any pending writes on the same
     report id.  (uhidev_stop no longer does anything else -- to
     ensure no more interrupts, just use uhidev_close.)

- Fix uhidev_open/close locking -- uhidev now has an interruptible
  config lock held only on first open and last close by any report id
  in the device, to serialize the transition between zero and nonzero
  numbers of references which requires opening/closing pipes and
  allocating/freeing buffers.

- Make /dev/uhidN selnotify(POLLHUP) when the device is yanked.

- Factor uhid device lookup and reference counting and dying
  detection and so on into uhid_enter/exit.

- Nix struct uhid_softc::sc_access_lock.  This served no purpose but
  to confuse me when trying to understand the logic of this beast
  (and to ensure uhidev_write exclusion, but it was uninterruptible,
  which is wrong for something that implements userland operations,
  and didn't actually work because uhidev_write did nothing to
  coordinate between different report ids).

- Fix locking in select/poll.

- Use atomics to manage UHID_IMMED to keep it simple.  (sc_lock would
  be fine too but it makes the code more verbose.)

- Omit needless UHID_ASLP -- cv_broadcast already has this
  micro-optimization.

With these changes, my Pinebook survives

for i in `jot 100`; do
        echo '###' $i
        for j in `jot 16`; do
                usbhidctl -rf /dev/uhid$j >/dev/null &
        done
        wait
done

while plugging and unplugging uhid(4) devices (U2F keys), and the U2F
keys still work as U2F keys.

ok nick, mrg

XXX pullup-9
XXX pullup-8?

Note on ABI and pullups: This changes the layout of struct
uhidev_softc, but with the sole exception of ucycom(4) -- which at
the moment is completely broken and unusable -- the only members that
USB HID drivers use are sc_udev and sc_iface, which haven't changed.
The layout of struct uhidev, which is allocated by each USB HID
driver in its own softc structure, is unchanged.


To generate a diff of this commit:
cvs rdiff -u -r1.114 -r1.115 src/sys/dev/usb/uhid.c
cvs rdiff -u -r1.78 -r1.79 src/sys/dev/usb/uhidev.c
cvs rdiff -u -r1.20 -r1.21 src/sys/dev/usb/uhidev.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.