linux-kernel - Re: [PATCH v2] Input: usbtouchscreen

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Date:   Thu, 23 Jun 2022 08:59:52 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Input: usbtouchscreen - add driver_info sanity check

On Thu, Jun 23, 2022 at 08:24:46AM +0200, Johan Hovold wrote:
> Add a sanity check on the device id-table driver_info field to make sure
> we never access a type structure (and function pointers) outside of the
> device info array (e.g. if someone fails to ifdef a device-id entry).
> 
> Note that this also suppresses a compiler warning with -Warray-bounds
> (gcc-11.3.0) when compile-testing the driver without enabling any of
> the device type Kconfig options:
> 
>     drivers/input/touchscreen/usbtouchscreen.c: In function 'usbtouch_probe':
>     drivers/input/touchscreen/usbtouchscreen.c:1668:16:warning: array subscript <unknown> is outside array bounds of 'struct usbtouch_device_info[0]' [-Warray-bounds]
>      1668 |         type = &usbtouch_dev_info[id->driver_info];
> 
> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
> 
> Changes in v2
>  - use ARRAY_SIZE() for the sanity check (Dmitry)
>  - drop the dummy entry and combine the two patches as the sanity check
>    itself is enough to suppress the compiler warning (Dmitry)
>  - use -ENODEV instead of -EINVAL even if this means no error will be
>    logged in the unlikely event of a future driver bug

Is this on purpose or because I happened to have used this error code
when I suggested the change? I'm fine with returning -EINVAL there.

Thanks.

-- 
Dmitry