Re: [PATCH 3/4] media: subdev: Improve v4l2_subdev_enable/disable_streams_fallback

Sakari Ailus
2024-04-04T12:23:55Z

Moi,

Thanks for the patch.

On Thu, Apr 04, 2024 at 01:50:02PM +0300, Tomi Valkeinen wrote:
> v4l2_subdev_enable/disable_streams_fallback() supports falling back to
> .s_stream() for subdevs with a single source pad. It also tracks the
> enabled streams for that one pad in the sd->enabled_streams field.
>
> Tracking the enabled streams with sd->enabled_streams does not make
> sense, as with .s_stream() there can only be a single stream per pad.
> Thus, as the v4l2_subdev_enable/disable_streams_fallback() only supports
> a single source pad, all we really need is a boolean which tells whether
> streaming has been enabled on this pad or not.
>
> However, as we only need a true/false state for a pad (instead of
> tracking which streams have been enabled for a pad), we can easily
> extend the fallback mechanism to support multiple source pads as we only
> need to keep track of which pads have been enabled.
>
> Change the sd->enabled_streams field to sd->enabled_pads, which is a
> 64-bit bitmask tracking the enabled source pads. With this change we can
> remove the restriction that
> v4l2_subdev_enable/disable_streams_fallback() only supports a single
> soruce pad.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
> drivers/media/v4l2-core/v4l2-subdev.c | 68 ++++++++++++++++++++---------------
> include/media/v4l2-subdev.h | 9 +++--
> 2 files changed, 44 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 3b3310bce5d4..91298bb84e6b 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -2090,37 +2090,43 @@ static int v4l2_subdev_enable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
> u64 streams_mask)
> {
> struct device *dev = sd->entity.graph_obj.mdev->dev;
> - unsigned int i;
> int ret;
>
> /*
> * The subdev doesn't implement pad-based stream enable, fall back
> - * on the .s_stream() operation. This can only be done for subdevs that
> - * have a single source pad, as sd->enabled_streams is global to the
> - * subdev.
> + * on the .s_stream() operation.
> */
> if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
> return -EOPNOTSUPP;
>
> - for (i = 0; i < sd->entity.num_pads; ++i) {
> - if (i != pad && sd->entity.pads[i].flags & MEDIA_PAD_FL_SOURCE)
> - return -EOPNOTSUPP;
> - }
> + /*
> + * .s_stream() means there is no streams support, so only allowed stream
> + * is the imlicit stream 0.
> + */
> + if (streams_mask != BIT_ULL(0))
> + return -EOPNOTSUPP;
> +
> + /*
> + * We use a 64-bit bitmask for tracking enabled pads, so only subdevices
> + * with 64 pads or less can be supported.
> + */
> + if (pad >= sizeof(sd->enabled_pads) * 8)

s/8/BITS_PER_BYTE/

> + return -EOPNOTSUPP;
>
> - if (sd->enabled_streams & streams_mask) {
> - dev_dbg(dev, "set of streams %#llx already enabled on %s:%u\n",
> - streams_mask, sd->entity.name, pad);
> + if (sd->enabled_pads & BIT_ULL(pad)) {
> + dev_dbg(dev, "pad %u already enabled on %s\n",
> + pad, sd->entity.name);
> return -EALREADY;
> }
>
> - /* Start streaming when the first streams are enabled. */
> - if (!sd->enabled_streams) {
> + /* Start streaming when the first pad is enabled. */
> + if (!sd->enabled_pads) {
> ret = v4l2_subdev_call(sd, video, s_stream, 1);
> if (ret)
> return ret;
> }
>
> - sd->enabled_streams |= streams_mask;
> + sd->enabled_pads |= BIT_ULL(pad);
>
> return 0;
> }
> @@ -2207,37 +2213,43 @@ static int v4l2_subdev_disable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
> u64 streams_mask)
> {
> struct device *dev = sd->entity.graph_obj.mdev->dev;
> - unsigned int i;
> int ret;
>
> /*
> - * If the subdev doesn't implement pad-based stream enable, fall back
> - * on the .s_stream() operation. This can only be done for subdevs that
> - * have a single source pad, as sd->enabled_streams is global to the
> - * subdev.
> + * If the subdev doesn't implement pad-based stream enable, fall back
> + * on the .s_stream() operation.
> */
> if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
> return -EOPNOTSUPP;
>
> - for (i = 0; i < sd->entity.num_pads; ++i) {
> - if (i != pad && sd->entity.pads[i].flags & MEDIA_PAD_FL_SOURCE)
> - return -EOPNOTSUPP;
> - }
> + /*
> + * .s_stream() means there is no streams support, so only allowed stream
> + * is the imlicit stream 0.
> + */
> + if (streams_mask != BIT_ULL(0))
> + return -EOPNOTSUPP;
> +
> + /*
> + * We use a 64-bit bitmask for tracking enabled pads, so only subdevices
> + * with 64 pads or less can be supported.
> + */
> + if (pad >= sizeof(sd->enabled_pads) * 8)

Ditto.

How much of the code of the two functions is the same? Could some of this
be put to a common function both would call? They look (almost) exactly the
same.

> + return -EOPNOTSUPP;
>
> - if ((sd->enabled_streams & streams_mask) != streams_mask) {
> - dev_dbg(dev, "set of streams %#llx already disabled on %s:%u\n",
> - streams_mask, sd->entity.name, pad);
> + if ((sd->enabled_pads & BIT_ULL(pad)) != BIT_ULL(pad)) {
> + dev_dbg(dev, "pad %u already disabled on %s\n",
> + pad, sd->entity.name);
> return -EALREADY;
> }
>
> /* Stop streaming when the last streams are disabled. */
> - if (!(sd->enabled_streams & ~streams_mask)) {
> + if (!(sd->enabled_pads & ~BIT_ULL(pad))) {
> ret = v4l2_subdev_call(sd, video, s_stream, 0);
> if (ret)
> return ret;
> }
>
> - sd->enabled_streams &= ~streams_mask;
> + sd->enabled_pads &= ~BIT_ULL(pad);
>
> return 0;
> }
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 8bd1e3c96d2b..7077aec3176c 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -1039,10 +1039,9 @@ struct v4l2_subdev_platform_data {
> * @active_state: Active state for the subdev (NULL for subdevs tracking the
> * state internally). Initialized by calling
> * v4l2_subdev_init_finalize().
> - * @enabled_streams: Bitmask of enabled streams used by
> - * v4l2_subdev_enable_streams() and
> - * v4l2_subdev_disable_streams() helper functions for fallback
> - * cases.
> + * @enabled_pads: Bitmask of enabled pads used by v4l2_subdev_enable_streams()
> + * and v4l2_subdev_disable_streams() helper functions for
> + * fallback cases.
> * @streaming_enabled: Tracks whether streaming has been enabled with s_stream.
> *
> * Each instance of a subdev driver should create this struct, either
> @@ -1091,7 +1090,7 @@ struct v4l2_subdev {
> * doesn't support it.
> */
> struct v4l2_subdev_state *active_state;
> - u64 enabled_streams;
> + u64 enabled_pads;
> bool streaming_enabled;
> };
>
>

--
Kind regards,

Sakari Ailus