Re: [Qemu-devel] [PATCH v3] ps2: set ps/2 output buffer size as the same as kernel

[Gerd Hoffmann]

  Hi,

> > If the kernel has booted up, the check will not happen, so the Linux kernel 
> > will not get confused.
>  
> I didn't find that the checking is necessary in protocol docs.
> any hint?
> 
> If we still use 256 size buffer in qemu, guest ps2 driver will drop
> some input keys? or just delay them?

Real hardware has a 16 byte buffer.  linux kernel ps/2 driver flushes
everything at initialization time, probably to avoid processing stale
data / incomplete ps/2 data sequences.  That flush loop is limited to 16
iterations, and if the kernel maxes out the loop it is confused and
fails initialization -> non-functional keyboard.

cheers,
  Gerd