linux-kernel - Re: [PATCH] HID: i2c-hid: ensure various commands do not interfere with each other

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Message-ID: <nycvar.YFH.7.76.2409111526450.31206@cbobk.fhfr.pm>
Date: Wed, 11 Sep 2024 15:27:32 +0200 (CEST)
From: Jiri Kosina <jikos@...nel.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
cc: ". Benjamin Tissoires" <bentiss@...nel.org>, 
    Douglas Anderson <dianders@...omium.org>, 
    Hans de Goede <hdegoede@...hat.com>, Kenny Levinsen <kl@...wtf>, 
    linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: i2c-hid: ensure various commands do not interfere
 with each other

On Mon, 9 Sep 2024, Dmitry Torokhov wrote:

> i2c-hid uses 2 shared buffers: command and "raw" input buffer for
> sending requests to peripherals and read data from peripherals when
> executing variety of commands. Such commands include reading of HID
> registers, requesting particular power mode, getting and setting
> reports and so on. Because all such requests use the same 2 buffers
> they should not execute simultaneously.
> 
> Fix this by introducing "cmd_lock" mutex and acquire it whenever
> we needs to access ihid->cmdbuf or idid->rawbuf.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>

Thanks for the fix, Dmitry. Out of curiosity, did you find it by code 
inspection, or have you actually seen it happening for real, making the 
driver misbehave?

Thanks,

-- 
Jiri Kosina
SUSE Labs