Re: [PATCH v8 2/9] media: v4l: Support obtaining link frequency via get_mbus_config

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

Hi,

On 17/12/2024 23:54, Sakari Ailus wrote:
> Add link_freq field to struct v4l2_mbus_config in order to pass the link
> frequency to the receiving sub-device.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>   drivers/media/v4l2-core/v4l2-common.c | 15 +++++++++++++--
>   include/media/v4l2-mediabus.h         |  2 ++
>   2 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 9fe74c7e064f..e4b2de3833ee 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -508,12 +508,23 @@ EXPORT_SYMBOL_GPL(__v4l2_get_link_freq_ctrl);
>   s64 __v4l2_get_link_freq_pad(struct media_pad *pad, unsigned int mul,
>   			     unsigned int div)
>   {
> +	struct v4l2_mbus_config mbus_config = {};
>   	struct v4l2_subdev *sd;
> +	int ret;
>   
>   	sd = media_entity_to_v4l2_subdev(pad->entity);
> -	if (!sd)
> -		return -ENODEV;
> +	ret = v4l2_subdev_call(sd, pad, get_mbus_config, pad->index,
> +			       &mbus_config);
> +	if (ret < 0 && ret != -ENOIOCTLCMD)
> +		return ret;
> +
> +	if (mbus_config.link_freq)
> +		return mbus_config.link_freq;
>   
> +	/*
> +	 * Fall back to using the link frequency control if the media bus config
> +	 * doesn't provide a link frequency.
> +	 */
>   	return __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div);
>   }
>   EXPORT_SYMBOL_GPL(__v4l2_get_link_freq_pad);
> diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h
> index e7f019f68c8d..24c738cd7894 100644
> --- a/include/media/v4l2-mediabus.h
> +++ b/include/media/v4l2-mediabus.h
> @@ -169,6 +169,7 @@ enum v4l2_mbus_type {
>   /**
>    * struct v4l2_mbus_config - media bus configuration
>    * @type: interface type
> + * @link_freq: The link frequency. See also V4L2_CID_LINK_FREQ control.
>    * @bus: bus configuration data structure
>    * @bus.parallel: embedded &struct v4l2_mbus_config_parallel.
>    *		  Used if the bus is parallel or BT.656.
> @@ -183,6 +184,7 @@ enum v4l2_mbus_type {
>    */
>   struct v4l2_mbus_config {
>   	enum v4l2_mbus_type type;
> +	u64 link_freq;
>   	union {
>   		struct v4l2_mbus_config_parallel parallel;
>   		struct v4l2_mbus_config_mipi_csi1 mipi_csi1;

Maybe the docs (V4L2_CID_LINK_FREQ and/or struct v4l2_mbus_config?) 
should mention that only if v4l2_mbus_config.link_freq is == 0, 
V4L2_CID_LINK_FREQ is used. Or, in other words, the driver must only use 
one of those methods.

  Tomi