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Re: [Qemu-devel] [PATCH] ps2: take exact use of ps2 buffer

From: Yang Hongyang
Subject: Re: [Qemu-devel] [PATCH] ps2: take exact use of ps2 buffer
Date: Thu, 2 Jun 2016 17:19:12 +0800

Hi Gerd,
  Thanks for reply!

On Thu, Jun 2, 2016 at 4:37 PM, Gerd Hoffmann <address@hidden> wrote:

> On Do, 2016-06-02 at 14:05 +0800, Yang Hongyang wrote:
> > According to PS/2 Mouse/Keyboard Protocol, the keyboard output buffer
> > size is 16 bytes, but we only use 15 bytes actually, this causes some
> > problem, for example, if I submit "123456789" in a bunch through VNC,
> > the actual result will be "12345678888888888...", because the 16th key
> > event which is "8" key up is dropped.
> What if you try a 10-char string next?

Actually I've tested this patch, I submit multiple 10-char string, things
as expected, it only takes the first 8-char.

> Things are failing again.
> Keyboards are low-bandwidth devices, you can't flood them with data and
> expect things to work.

The poin is not about to make it work with more then 8 string, it is to
make it competible with the protocol, which is a 16-bytes buffer, apparantly
we are not following this and which do cause the problem.
This chunk of code originally uses full QUEUE_SIZE buffer, and in
this commit 2858ab09e6f708e3, it changes the behaviour implicitly.

> Try this one instead: https://patchwork.ozlabs.org/patch/628491/

This seems like a good feature, we will use this, thanks, but it's not
related to
this patch.

> cheers,
>   Gerd


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