drm/ssd130x: Set SPI .id_table to prevent an SPI core warning

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 member 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 member 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.

Fixes: 74373977d2ca ("drm/solomon: Add SSD130x OLED displays SPI support")
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Javier Martinez Canillas <[e-mail]>

drivers/gpu/drm/solomon/ssd130x-spi.c

···
 };
 MODULE_DEVICE_TABLE(of, ssd130x_of_match);
 
-#if IS_MODULE(CONFIG_DRM_SSD130X_SPI)
 /*
  * The SPI core always reports a MODALIAS uevent of the form "spi:<dev>", even
  * if the device was registered via OF. This means that the module will not be
···
  * To workaround this issue, add a SPI device ID table. Even when this should
  * not be needed for this driver to match the registered SPI devices.
  */
-static const struct spi_device_id ssd130x_spi_table[] = {
+static const struct spi_device_id ssd130x_spi_id[] = {
 	/* ssd130x family */
 	{ "sh1106",  SH1106_ID },
 	{ "ssd1305", SSD1305_ID },
···
 	{ "ssd1331", SSD1331_ID },
 	{ /* sentinel */ }
 };
-MODULE_DEVICE_TABLE(spi, ssd130x_spi_table);
-#endif
+MODULE_DEVICE_TABLE(spi, ssd130x_spi_id);
 
 static struct spi_driver ssd130x_spi_driver = {
 	.driver = {
 		.name = DRIVER_NAME,
 		.of_match_table = ssd130x_of_match,
 	},
+	.id_table = ssd130x_spi_id,
 	.probe = ssd130x_spi_probe,
 	.remove = ssd130x_spi_remove,
 	.shutdown = ssd130x_spi_shutdown,