Re: [PATCH] drm/bridge-connector: select DRM_DISPLAY_HELPER from DRM_BRIDGE_CONNECTOR

["Arnd Bergmann" <arnd@arndb.de>]

On Fri, Oct 18, 2024, at 15:42, Dmitry Baryshkov wrote:
> On Fri, Oct 18, 2024 at 03:08:45PM +0000, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>> 
>> The imx display drivers use the new bridge connector helpers but don't
>> explicitly select CONFIG_DRM_DISPLAY_HELPER, leading to a link failure
>> in rare configurations:
>> 
>> ld.lld-20: error: undefined symbol: drm_bridge_connector_init
>> >>> referenced by imx-ldb.c
>> >>>               drivers/gpu/drm/imx/ipuv3/imx-ldb.o:(imx_ldb_bind) in archive vmlinux.a
>> >>> referenced by parallel-display.c
>> >>>               drivers/gpu/drm/imx/ipuv3/parallel-display.o:(imx_pd_bind) in archive vmlinux.a
>> 
>> Move DRM_BRIDGE_CONNECTOR out of the DRM_DISPLAY_HELPER block and
>> instead select that symbol indirectly.
>> 
>> Fixes: f94b9707a1c9 ("drm/imx: parallel-display: switch to imx_legacy_bridge / drm_bridge_connector")
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> I think a correct fix is to select DRM_DISPLAY_HELPER instead.

I think I just didn't express that clearly enough, selecting
DRM_DISPLAY_HELPER is what I did and what I tried to explain:

>>  config DRM_BRIDGE_CONNECTOR
>>  	bool
>>  	select DRM_DISPLAY_HDMI_STATE_HELPER
>> +	select DRM_DISPLAY_HELPER
>>  	help
>>  	  DRM connector implementation terminating DRM bridge chains.

I had to move the 'if' block just to avoid a circular
dependency.

Or did you mean the imx driver is the one that should
'select DRM_DISPLAY_HELPER'? That would also work, but
adds a bit more complexity.

      Arnd