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

Laurent Pinchart
2024-04-04T14:25:27Z

On Thu, Apr 04, 2024 at 04:47:41PM +0300, Tomi Valkeinen wrote:
> On 04/04/2024 16:06, Laurent Pinchart wrote:
> > 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/
>
> Actually, now that we support multiple pads here... Should the comment
> and the if below, checking whether the pad is a source pad, be removed?
> Is there any reason to require a source pad here (but not in the
> non-fallback case)?

Mostly the lack of test platforms where we handle stream start/stop from
source to sink, calling the operations on sink pads. I'm sure there will
be unforeseen issues :-)

> > 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