Re: [PATCH v8 03/36] media: subdev: add 'which' to subdev state

[Jacopo Mondi <jacopo@jmondi.org>]

Hi Tomi,

On Mon, Aug 30, 2021 at 02:00:43PM +0300, Tomi Valkeinen wrote:
> The subdev state is passed to functions in the media drivers, and
> usually either V4L2_SUBDEV_FORMAT_ACTIVE or V4L2_SUBDEV_FORMAT_TRY is
> also given to the function in one way or another.
>
> One op where this is not the case is v4l2_subdev_pad_ops.init_cfg. One
> could argue that the initialization of the state should be the same for
> both ACTIVE and TRY cases, but unfortunately that is not the case:
>
> - Some drivers do also other things than just touch the state when
> dealing with ACTIVE, e.g. if there is extra state outside the standard
> subdev state.
> - Some drivers might need to create, say, struct v4l2_subdev_format
> which has 'which' field, and that needs to be filled with either ACTIVE
> or TRY.
>
> Currently init_cfg is only called for TRY case from the v4l2 framework,
> passing the TRY state. Some drivers call their own init_cfg, passing
> NULL as the state, which is used to indicate ACTIVE case.
>
> In the future we want to pass subdev's active state from the v4l2
> framework side, so we need a solution to this.
>
> We could change the init_cfg() to include the TRY/ACTIVE value, which
> would require changing more or less all the drivers. Instead, I have
> added 'which' field to the subdev state itself, filled at state
> allocation time, which only requires changes to the drivers that
> allocate a state themselves.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  drivers/media/platform/rcar-vin/rcar-v4l2.c |  2 +-
>  drivers/media/platform/vsp1/vsp1_entity.c   |  2 +-
>  drivers/media/v4l2-core/v4l2-subdev.c       | 10 +++++++---
>  drivers/staging/media/tegra-video/vi.c      |  2 +-
>  include/media/v4l2-subdev.h                 |  7 ++++++-
>  5 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-v4l2.c b/drivers/media/platform/rcar-vin/rcar-v4l2.c
> index 5f4fa8c48f68..1de30d5b437f 100644
> --- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
> +++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
> @@ -252,7 +252,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
>  	u32 width, height;
>  	int ret;
>
> -	sd_state = v4l2_alloc_subdev_state(sd);
> +	sd_state = v4l2_alloc_subdev_state(sd, V4L2_SUBDEV_FORMAT_ACTIVE);

Shouldn't the 'which' parameters be used to decide if either ACTIVE or
TRY have to be used ? this function is also used to set TRY formats,
in example...

Oh, maybe I got how it works, the state's which is not
relevant but the v4l2_subdev_format's which is, as it will be used in
the next patch to decide if the subdev's state of the file-handle's
state should be passed to the ioctl.

>  	if (IS_ERR(sd_state))
>  		return PTR_ERR(sd_state);
>
> diff --git a/drivers/media/platform/vsp1/vsp1_entity.c b/drivers/media/platform/vsp1/vsp1_entity.c
> index e40bca254b8b..63ea5e472c33 100644
> --- a/drivers/media/platform/vsp1/vsp1_entity.c
> +++ b/drivers/media/platform/vsp1/vsp1_entity.c
> @@ -675,7 +675,7 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
>  	 * Allocate the pad configuration to store formats and selection
>  	 * rectangles.
>  	 */
> -	entity->config = v4l2_alloc_subdev_state(&entity->subdev);
> +	entity->config = v4l2_alloc_subdev_state(&entity->subdev, V4L2_SUBDEV_FORMAT_ACTIVE);
>  	if (IS_ERR(entity->config)) {
>  		media_entity_cleanup(&entity->subdev.entity);
>  		return PTR_ERR(entity->config);
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index e1a794f69815..04ad319fb150 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -28,7 +28,7 @@ static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
>  {
>  	struct v4l2_subdev_state *state;
>
> -	state = v4l2_alloc_subdev_state(sd);
> +	state = v4l2_alloc_subdev_state(sd, V4L2_SUBDEV_FORMAT_TRY);

At the same time I'm not sure I get the purpose of this. Don't
init_cfg() callback implementations deal with try formats themeselves
? I mean, it's not a fixed rule, they can as well initialize their
default 'active' formats, but what matters is that they initialize
their per-fh try states ?

Shouldn't init_cfg receive the fh's state so that it can initialize
it, and just in case they need to, access their subdev's state and
initialize them ? I'm missing what the purpose of the flag is tbh.

Thanks
   j


>  	if (IS_ERR(state))
>  		return PTR_ERR(state);
>
> @@ -870,7 +870,9 @@ int v4l2_subdev_link_validate(struct media_link *link)
>  }
>  EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
>
> -struct v4l2_subdev_state *v4l2_alloc_subdev_state(struct v4l2_subdev *sd)
> +struct v4l2_subdev_state *
> +v4l2_alloc_subdev_state(struct v4l2_subdev *sd,
> +			enum v4l2_subdev_format_whence which)
>  {
>  	struct v4l2_subdev_state *state;
>  	int ret;
> @@ -879,6 +881,8 @@ struct v4l2_subdev_state *v4l2_alloc_subdev_state(struct v4l2_subdev *sd)
>  	if (!state)
>  		return ERR_PTR(-ENOMEM);
>
> +	state->which = which;
> +
>  	if (sd->entity.num_pads) {
>  		state->pads = kvmalloc_array(sd->entity.num_pads,
>  					     sizeof(*state->pads),
> @@ -948,7 +952,7 @@ int v4l2_subdev_alloc_state(struct v4l2_subdev *sd)
>  {
>  	struct v4l2_subdev_state *state;
>
> -	state = v4l2_alloc_subdev_state(sd);
> +	state = v4l2_alloc_subdev_state(sd, V4L2_SUBDEV_FORMAT_ACTIVE);
>  	if (IS_ERR(state))
>  		return PTR_ERR(state);
>
> diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
> index a94d19e2a67c..691f5e04b0a1 100644
> --- a/drivers/staging/media/tegra-video/vi.c
> +++ b/drivers/staging/media/tegra-video/vi.c
> @@ -507,7 +507,7 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
>  	if (!subdev)
>  		return -ENODEV;
>
> -	sd_state = v4l2_alloc_subdev_state(subdev);
> +	sd_state = v4l2_alloc_subdev_state(subdev, V4L2_SUBDEV_FORMAT_ACTIVE);
>  	if (IS_ERR(sd_state))
>  		return PTR_ERR(sd_state);
>  	/*
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index ecaf040ead57..5ec78ffda4f5 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -655,6 +655,7 @@ struct v4l2_subdev_pad_config {
>  /**
>   * struct v4l2_subdev_state - Used for storing subdev state information.
>   *
> + * @which: state type (from enum v4l2_subdev_format_whence)
>   * @pads: &struct v4l2_subdev_pad_config array
>   *
>   * This structure only needs to be passed to the pad op if the 'which' field
> @@ -662,6 +663,7 @@ struct v4l2_subdev_pad_config {
>   * %V4L2_SUBDEV_FORMAT_ACTIVE it is safe to pass %NULL.
>   */
>  struct v4l2_subdev_state {
> +	u32 which;
>  	struct v4l2_subdev_pad_config *pads;
>  };
>
> @@ -1141,10 +1143,13 @@ int v4l2_subdev_link_validate(struct media_link *link);
>   * v4l2_alloc_subdev_state - allocate v4l2_subdev_state
>   *
>   * @sd: pointer to &struct v4l2_subdev for which the state is being allocated.
> + * @which: configuration type for the state (from enum v4l2_subdev_format_whence)
>   *
>   * Must call v4l2_free_subdev_state() when state is no longer needed.
>   */
> -struct v4l2_subdev_state *v4l2_alloc_subdev_state(struct v4l2_subdev *sd);
> +struct v4l2_subdev_state *
> +v4l2_alloc_subdev_state(struct v4l2_subdev *sd,
> +			enum v4l2_subdev_format_whence which);
>
>  /**
>   * v4l2_free_subdev_state - free a v4l2_subdev_state
> --
> 2.25.1
>