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

Laurent Pinchart
2024-04-04T13:06:30Z

On Thu, Apr 04, 2024 at 03:38:45PM +0300, Tomi Valkeinen wrote:
> On 04/04/2024 15:18, Sakari Ailus wrote:
> > 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.

s/soruce/source/

> >>
> >> 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.

While at it, s/on/to/

Same below.

> >> */
> >> 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.

s/imlicit/implicit/

Same below.

> >> + */
> >> + 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.
>
> v4l2_subdev_enable_streams_fallback and v4l2_subdev_enable_streams? They
> have similar parts, but I don't right away see how combining them or
> making some common functions would help.

You could move the three checks to a
v4l2_subdev_streams_fallback_check() function (bikeshedding the name is
allowed).

> >> + 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)) {

if (!(sd->enabled_pads & 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;
> >> };
> >>

--
Regards,

Laurent Pinchart