linux-kernel - Re: [PATCH] drm/ssd130x: Set SPI .id_table to prevent an SPI core warning

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Message-ID: <p2hzb3ysmthgfi4j6ehwulzk44zf4s5d6bm3nqs2rww47boshl@jr6aqmas4l5p>
Date: Tue, 31 Dec 2024 16:36:34 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Javier Martinez Canillas <javierm@...hat.com>
Cc: linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>, 
	David Airlie <airlied@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Simona Vetter <simona@...ll.ch>, 
	Thomas Zimmermann <tzimmermann@...e.de>, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/ssd130x: Set SPI .id_table to prevent an SPI core
 warning

On Tue, Dec 31, 2024 at 12:44:58PM +0100, Javier Martinez Canillas wrote:
> The only reason for the ssd130x-spi driver to have an spi_device_id table
> is that the SPI core always reports an "spi:" MODALIAS, even when the SPI
> device has been registered via a Device Tree Blob.
> 
> Without spi_device_id table information in the module's metadata, module
> autoloading would not work because there won't be an alias that matches
> the MODALIAS reported by the SPI core.
> 
> This spi_device_id table is not needed for device matching though, since
> the of_device_id table is always used in this case. For this reason, the
> struct spi_driver .id_table field is currently not set in the SPI driver.
> 
> Because the spi_device_id table is always required for module autoloading,
> the SPI core checks during driver registration that both an of_device_id
> table and a spi_device_id table are present and that they contain the same
> entries for all the SPI devices.
> 
> Not setting the .id_table field in the driver then confuses the core and
> leads to the following warning when the ssd130x-spi driver is registered:
> 
>   [   41.091198] SPI driver ssd130x-spi has no spi_device_id for sinowealth,sh1106
>   [   41.098614] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1305
>   [   41.105862] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1306
>   [   41.113062] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1307
>   [   41.120247] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1309
>   [   41.127449] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1322
>   [   41.134627] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1325
>   [   41.141784] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1327
>   [   41.149021] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1331
> 
> To prevent the warning, set the .id_table even though it's not necessary.
> 
> Since the check is done even for built-in drivers, drop the condition to
> only define the ID table when the driver is built as a module. Finally,
> rename the variable to use the "_spi_id" convention used for ID tables.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>

Fixes: 74373977d2ca ("drm/solomon: Add SSD130x OLED displays SPI support")

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>


> ---
> 
>  drivers/gpu/drm/solomon/ssd130x-spi.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 

-- 
With best wishes
Dmitry