linux-kernel - Re: [PATCH 1/4] drm: Add I2C connector type

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Date:   Tue, 1 Feb 2022 13:58:16 +0100
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Sam Ravnborg <sam@...nborg.org>,
        Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        dri-devel@...ts.freedesktop.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Maxime Ripard <maxime@...no.tech>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Emil Velikov <emil.l.velikov@...il.com>
Subject: Re: [PATCH 1/4] drm: Add I2C connector type



Den 31.01.2022 21.52, skrev Sam Ravnborg:
> On Mon, Jan 31, 2022 at 09:12:21PM +0100, Javier Martinez Canillas wrote:
>> There isn't a connector type for display controllers accesed through I2C,
>> most drivers use DRM_MODE_CONNECTOR_Unknown or DRM_MODE_CONNECTOR_VIRTUAL.
>>
>> Add an I2C connector type to match the actual connector.
>>
>> As Noralf Trønnes mentions in commit fc06bf1d76d6 ("drm: Add SPI connector
>> type"), user-space should be able to cope with a connector type that does
>> not yet understand.
>>

It turned out that I wasn't entirely correct here, mpv didn't cope with
unknown types. In the PR to add support Emil Velikov wondered if libdrm
should handle these connector names:
https://github.com/mpv-player/mpv/pull/8989#issuecomment-879187711

>> Tested with `modetest -M ssd1307 -c` and shows the connector as unknown-1.
> I had expected unknown-21??
> 
>>
>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> Reviewed-by: Sam Ravnborg <sam@...nborg.org>

Sam, didn't you and Laurent discuss adding DRM_MODE_CONNECTOR_PANEL for
such a use case?

If someone adds parallel bus support to the MIPI DBI helper, there will
be one more connector type (I wonder what that one will be called).

Noralf.

>> ---
>>
>>  drivers/gpu/drm/drm_connector.c | 1 +
>>  include/uapi/drm/drm_mode.h     | 1 +
>>  2 files changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
>> index a50c82bc2b2f..975a7525a508 100644
>> --- a/drivers/gpu/drm/drm_connector.c
>> +++ b/drivers/gpu/drm/drm_connector.c
>> @@ -105,6 +105,7 @@ static struct drm_conn_prop_enum_list drm_connector_enum_list[] = {
>>  	{ DRM_MODE_CONNECTOR_WRITEBACK, "Writeback" },
>>  	{ DRM_MODE_CONNECTOR_SPI, "SPI" },
>>  	{ DRM_MODE_CONNECTOR_USB, "USB" },
>> +	{ DRM_MODE_CONNECTOR_I2C, "I2C" },
>>  };
>>  
>>  void drm_connector_ida_init(void)
>> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
>> index e1e351682872..d6d6288242db 100644
>> --- a/include/uapi/drm/drm_mode.h
>> +++ b/include/uapi/drm/drm_mode.h
>> @@ -421,6 +421,7 @@ enum drm_mode_subconnector {
>>  #define DRM_MODE_CONNECTOR_WRITEBACK	18
>>  #define DRM_MODE_CONNECTOR_SPI		19
>>  #define DRM_MODE_CONNECTOR_USB		20
>> +#define DRM_MODE_CONNECTOR_I2C		21
>>  
>>  /**
>>   * struct drm_mode_get_connector - Get connector metadata.
>> -- 
>> 2.34.1