Re: [Qemu-devel] [PATCH] virtio-input: implement pass-through evdev writes

[Gerd Hoffmann <kraxel@redhat.com>]

On Fr, 2016-04-01 at 11:31 +0200, Ladi Prosek wrote:
> The write path for pass-through devices, commonly used for controlling
> keyboard LEDs via EV_LED, was not implemented. This commit adds the
> necessary plumbing to connect the status virtio queue to the host evdev
> file descriptor.
> 
> Signed-off-by: Ladi Prosek <lprosek@redhat.com>
> ---
> Most of the new code has to do with handling EAGAIN/EWOULDBLOCK. I don't
> believe that this will be happening in practise for local evdev devices.

Agree.

> Of course, all bets are off if fd is an arbitrary file,

It can't be, it would fail the evdev ioctls.

> with the event stream). So part of me would just do one best-effort
> write and ignore all errors. I'm curious what you think. 

Just do best-effort sounds reasonable to me.

The code to handle EGAIN will just bitrot b/c it will never be used (and
I guess it is untested too, or did you manage to provoke EGAIN somehow?)

cheers,
  Gerd