On Wed, Apr 24, 2024 at 04:11:36PM +0300, Tomi Valkeinen wrote:
> On 24/04/2024 16:09, Laurent Pinchart wrote:
> > On Wed, Apr 24, 2024 at 04:05:31PM +0300, Tomi Valkeinen wrote:
> >> On 19/04/2024 18:36, Laurent Pinchart wrote:
> >>> On Tue, Apr 16, 2024 at 04:55:12PM +0300, Tomi Valkeinen wrote:
> >>>> At the moment the v4l2_subdev_enable/disable_streams() functions call
> >>>> fallback helpers to handle the case where the subdev only implements
> >>>> .s_stream(), and the main function handles the case where the subdev
> >>>> implements streams (V4L2_SUBDEV_FL_STREAMS, which implies
> >>>> .enable/disable_streams()).
> >>>>
> >>>> What is missing is support for subdevs which do not implement streams
> >>>> support, but do implement .enable/disable_streams(). Example cases of
> >>>> these subdevices are single-stream cameras, where using
> >>>> .enable/disable_streams() is not required but helps us remove the users
> >>>> of the legacy .s_stream(), and subdevices with multiple source pads (but
> >>>> single stream per pad), where .enable/disable_streams() allows the
> >>>> subdevice to control the enable/disable state per pad.
> >>>>
> >>>> The two single-streams cases (.s_stream() and .enable/disable_streams())
> >>>> are very similar, and with small changes we can change the
> >>>> v4l2_subdev_enable/disable_streams() functions to support all three
> >>>> cases, without needing separate fallback functions.
> >>>>
> >>>> A few potentially problematic details, though:
> >>>>
> >>>> - For the single-streams cases we use sd->enabled_pads field, which
> >>>> limits the number of pads for the subdevice to 64. For simplicity I
> >>>> added the check for this limitation to the beginning of the function,
> >>>> and it also applies to the streams case.
> >>>>
> >>>> - The fallback functions only allowed the target pad to be a source pad.
> >>>> It is not very clear to me why this check was needed, but it was not
> >>>> needed in the streams case. However, I doubt the
> >>>> v4l2_subdev_enable/disable_streams() code has ever been tested with
> >>>> sink pads, so to be on the safe side, I added the same check
> >>>> to the v4l2_subdev_enable/disable_streams() functions.
> >>>>
> >>>
> >>> Now that v4l2_subdev_enable_streams() is usable by (almost) every
> >>> driver, should we update documentation to indicate that manual calls to
> >>> .s_stream() should be avoided ?
> >>
> >> How about:
> >>
> >> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> >> index dabe1b5dfe4a..f52bb790773c 100644
> >> --- a/include/media/v4l2-subdev.h
> >> +++ b/include/media/v4l2-subdev.h
> >> @@ -450,6 +450,11 @@ enum v4l2_subdev_pre_streamon_flags {
> >> * already started or stopped subdev. Also see call_s_stream wrapper in
> >> * v4l2-subdev.c.
> >> *
> >> + * New drivers should instead implement &v4l2_subdev_pad_ops.enable_streams
> >> + * and &v4l2_subdev_pad_ops.disable_streams operations, and use
> >> + * v4l2_subdev_s_stream_helper for the &v4l2_subdev_video_ops.s_stream
> >> + * operation to support legacy users.A
> >> + *
> >
> > Add
> >
> > * Drivers should also not call the .s_stream() subdev operation directly,
> > * but use the v4l2_subdev_enable_streams() and
> > * v4l2_subdev_disable_streams() helpers.
> >
> >> * @g_pixelaspect: callback to return the pixelaspect ratio.
> >> *
> >> * @s_dv_timings: Set custom dv timings in the sub device. This is used
> >>
> >>
> >> Although now that I think about it, can we "ever" get rid of s_stream?
> >> enable_streams is only usable if the subdev has pads.
> >
> > Do we have pad-less subdevs that can stream ?
>
> Probably not, but isn't s_stream used to enable any type of subdev? Or
> is there a different op to power on padless subdevs?
.s_stream() is supposed to start/stop streaming, and you can't really
have streams without pads, as they have to come from/go somewhere.
> >> If that's the
> >> case, the text above should probably clarify when one should continue
> >> using s_stream.
> >>
> >>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
> >>>> ---
> >>>> drivers/media/v4l2-core/v4l2-subdev.c | 187 ++++++++++++++--------------------
> >>>> 1 file changed, 79 insertions(+), 108 deletions(-)
> >>>>
> >>>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> >>>> index e45fd42da1e3..10406acfb9d0 100644
> >>>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> >>>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> >>>> @@ -2106,6 +2106,13 @@ static void v4l2_subdev_collect_streams(struct v4l2_subdev *sd,
> >>>> u64 *found_streams,
> >>>> u64 *enabled_streams)
> >>>> {
> >>>> + if (!(sd->flags & V4L2_SUBDEV_FL_STREAMS)) {
> >>>> + *found_streams = BIT_ULL(0);
> >>>> + *enabled_streams =
> >>>> + (sd->enabled_pads & BIT_ULL(pad)) ? BIT_ULL(0) : 0;
> >>>> + return;
> >>>> + }
> >>>> +
> >>>> *found_streams = 0;
> >>>> *enabled_streams = 0;
> >>>>
> >>>> @@ -2127,6 +2134,14 @@ static void v4l2_subdev_set_streams_enabled(struct v4l2_subdev *sd,
> >>>> u32 pad, u64 streams_mask,
> >>>> bool enabled)
> >>>> {
> >>>> + if (!(sd->flags & V4L2_SUBDEV_FL_STREAMS)) {
> >>>> + if (enabled)
> >>>> + sd->enabled_pads |= BIT_ULL(pad);
> >>>> + else
> >>>> + sd->enabled_pads &= ~BIT_ULL(pad);
> >>>> + return;
> >>>> + }
> >>>> +
> >>>> for (unsigned int i = 0; i < state->stream_configs.num_configs; ++i) {
> >>>> struct v4l2_subdev_stream_config *cfg =
> >>>> &state->stream_configs.configs[i];
> >>>> @@ -2136,51 +2151,6 @@ static void v4l2_subdev_set_streams_enabled(struct v4l2_subdev *sd,
> >>>> }
> >>>> }
> >>>>
> >>>> -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;
> >>>> - int ret;
> >>>> -
> >>>> - /*
> >>>> - * The subdev doesn't implement pad-based stream enable, fall back
> >>>> - * to the .s_stream() operation.
> >>>> - */
> >>>> - if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
> >>>> - return -EOPNOTSUPP;
> >>>> -
> >>>> - /*
> >>>> - * .s_stream() means there is no streams support, so the only allowed
> >>>> - * stream is the implicit 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) * BITS_PER_BYTE)
> >>>> - return -EOPNOTSUPP;
> >>>> -
> >>>> - 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 pad is enabled. */
> >>>> - if (!sd->enabled_pads) {
> >>>> - ret = v4l2_subdev_call(sd, video, s_stream, 1);
> >>>> - if (ret)
> >>>> - return ret;
> >>>> - }
> >>>> -
> >>>> - sd->enabled_pads |= BIT_ULL(pad);
> >>>> -
> >>>> - return 0;
> >>>> -}
> >>>> -
> >>>> int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>> u64 streams_mask)
> >>>> {
> >>>> @@ -2189,21 +2159,33 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>> bool already_streaming;
> >>>> u64 enabled_streams;
> >>>> u64 found_streams;
> >>>> + bool use_s_stream;
> >>>> int ret;
> >>>>
> >>>> /* A few basic sanity checks first. */
> >>>> if (pad >= sd->entity.num_pads)
> >>>> return -EINVAL;
> >>>>
> >>>> + if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
> >>>> + 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) * BITS_PER_BYTE)
> >>>> + return -EOPNOTSUPP;
> >>>> +
> >>>> if (!streams_mask)
> >>>> return 0;
> >>>>
> >>>> /* Fallback on .s_stream() if .enable_streams() isn't available. */
> >>>> - if (!v4l2_subdev_has_op(sd, pad, enable_streams))
> >>>> - return v4l2_subdev_enable_streams_fallback(sd, pad,
> >>>> - streams_mask);
> >>>> + use_s_stream = !v4l2_subdev_has_op(sd, pad, enable_streams);
> >>>>
> >>>> - state = v4l2_subdev_lock_and_get_active_state(sd);
> >>>> + if (!use_s_stream)
> >>>> + state = v4l2_subdev_lock_and_get_active_state(sd);
> >>>> + else
> >>>> + state = NULL;
> >>>>
> >>>> /*
> >>>> * Verify that the requested streams exist and that they are not
> >>>> @@ -2231,9 +2213,18 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>>
> >>>> already_streaming = v4l2_subdev_is_streaming(sd);
> >>>>
> >>>> - /* Call the .enable_streams() operation. */
> >>>> - ret = v4l2_subdev_call(sd, pad, enable_streams, state, pad,
> >>>> - streams_mask);
> >>>> + if (!use_s_stream) {
> >>>> + /* Call the .enable_streams() operation. */
> >>>> + ret = v4l2_subdev_call(sd, pad, enable_streams, state, pad,
> >>>> + streams_mask);
> >>>> + } else {
> >>>> + /* Start streaming when the first pad is enabled. */
> >>>> + if (!already_streaming)
> >>>> + ret = v4l2_subdev_call(sd, video, s_stream, 1);
> >>>> + else
> >>>> + ret = 0;
> >>>> + }
> >>>> +
> >>>> if (ret) {
> >>>> dev_dbg(dev, "enable streams %u:%#llx failed: %d\n", pad,
> >>>> streams_mask, ret);
> >>>> @@ -2243,34 +2234,32 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>> /* Mark the streams as enabled. */
> >>>> v4l2_subdev_set_streams_enabled(sd, state, pad, streams_mask, true);
> >>>
> >>> state gets set to a non-null value above if the subdev has an
> >>> enable_streams operation, while in v4l2_subdev_set_streams_enabled(),
> >>
> >> That's not quite true, v4l2_subdev_lock_and_get_active_state() returns
> >> NULL if there's no state. If the driver has .enable_streams but no
> >> subdev-state, we'll have NULL state. But is that a driver bug? Probably,
> >> although I'm not quite sure. Whereas V4L2_SUBDEV_FL_STREAMS without
> >> state is a driver bug.
> >>
> >>> you use it if the V4L2_SUBDEV_FL_STREAMS flag is set. The second
> >>> condition is a subset of the first one, so it should be safe now, but I
> >>> wonder if we're at risk of crashes in the future when reworking the
> >>> code. I'm probably worrying needlessly.
> >>
> >> I agree that this is a bit messy. We have multiple different scenarios
> >> which we handle in the same functions, and it's somewhat unclear what
> >> op/state/flag combinations the drivers are allowed to have and what not.
> >>
> >> I could add a !state check here, and then use sd->enabled_pads. But that
> >> doesn't feel correct, and I think it's just better to crash and then fix
> >> it if we end up there.
> >>
> >>>>
> >>>> - if (!already_streaming)
> >>>> + if (!use_s_stream && !already_streaming)
> >>>> v4l2_subdev_enable_privacy_led(sd);
> >>>
> >>> Once everybody switches to v4l2_subdev_enable_streams() (am I dreaming?)
> >>> we should move LED handling from the .s_stream() wrapper to here for the
> >>> fallback case too. How about a TODO comment ?
> >>
> >> Let's get back to this after we figure out if s_stream can ever be removed.
> >>
> >>>>
> >>>> done:
> >>>> - v4l2_subdev_unlock_state(state);
> >>>> + if (!use_s_stream)
> >>>
> >>> if (state)
> >>>
> >>> would be better I think.
> >>
> >> We get the state and state lock if (!use_s_stream), so I think it makes
> >> sense to use the same condition when unlocking to be symmetric. I'm sure
> >> I can be convinced to use if (state) too, though =).
> >>
> >>>> + v4l2_subdev_unlock_state(state);
> >>>>
> >>>> return ret;
> >>>> }
> >>>> EXPORT_SYMBOL_GPL(v4l2_subdev_enable_streams);
> >>>>
> >>>> -static int v4l2_subdev_disable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
> >>>> - u64 streams_mask)
> >>>> +int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>> + u64 streams_mask)
> >>>> {
> >>>> struct device *dev = sd->entity.graph_obj.mdev->dev;
> >>>> + struct v4l2_subdev_state *state;
> >>>> + u64 enabled_streams;
> >>>> + u64 found_streams;
> >>>> + bool use_s_stream;
> >>>> int ret;
> >>>>
> >>>> - /*
> >>>> - * If the subdev doesn't implement pad-based stream enable, fall back
> >>>> - * to the .s_stream() operation.
> >>>> - */
> >>>> - if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
> >>>> - return -EOPNOTSUPP;
> >>>> + /* A few basic sanity checks first. */
> >>>> + if (pad >= sd->entity.num_pads)
> >>>> + return -EINVAL;
> >>>>
> >>>> - /*
> >>>> - * .s_stream() means there is no streams support, so the only allowed
> >>>> - * stream is the implicit stream 0.
> >>>> - */
> >>>> - if (streams_mask != BIT_ULL(0))
> >>>> + if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
> >>>> return -EOPNOTSUPP;
> >>>>
> >>>> /*
> >>>> @@ -2280,46 +2269,16 @@ static int v4l2_subdev_disable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
> >>>> if (pad >= sizeof(sd->enabled_pads) * BITS_PER_BYTE)
> >>>> return -EOPNOTSUPP;
> >>>>
> >>>> - 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_pads & ~BIT_ULL(pad))) {
> >>>> - ret = v4l2_subdev_call(sd, video, s_stream, 0);
> >>>> - if (ret)
> >>>> - return ret;
> >>>> - }
> >>>> -
> >>>> - sd->enabled_pads &= ~BIT_ULL(pad);
> >>>> -
> >>>> - return 0;
> >>>> -}
> >>>> -
> >>>> -int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>> - u64 streams_mask)
> >>>> -{
> >>>> - struct device *dev = sd->entity.graph_obj.mdev->dev;
> >>>> - struct v4l2_subdev_state *state;
> >>>> - u64 enabled_streams;
> >>>> - u64 found_streams;
> >>>> - int ret;
> >>>> -
> >>>> - /* A few basic sanity checks first. */
> >>>> - if (pad >= sd->entity.num_pads)
> >>>> - return -EINVAL;
> >>>> -
> >>>> if (!streams_mask)
> >>>> return 0;
> >>>>
> >>>> /* Fallback on .s_stream() if .disable_streams() isn't available. */
> >>>> - if (!v4l2_subdev_has_op(sd, pad, disable_streams))
> >>>> - return v4l2_subdev_disable_streams_fallback(sd, pad,
> >>>> - streams_mask);
> >>>> + use_s_stream = !v4l2_subdev_has_op(sd, pad, disable_streams);
> >>>>
> >>>> - state = v4l2_subdev_lock_and_get_active_state(sd);
> >>>> + if (!use_s_stream)
> >>>> + state = v4l2_subdev_lock_and_get_active_state(sd);
> >>>> + else
> >>>> + state = NULL;
> >>>>
> >>>> /*
> >>>> * Verify that the requested streams exist and that they are not
> >>>> @@ -2345,9 +2304,19 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>>
> >>>> dev_dbg(dev, "disable streams %u:%#llx\n", pad, streams_mask);
> >>>>
> >>>> - /* Call the .disable_streams() operation. */
> >>>> - ret = v4l2_subdev_call(sd, pad, disable_streams, state, pad,
> >>>> - streams_mask);
> >>>> + if (!use_s_stream) {
> >>>> + /* Call the .disable_streams() operation. */
> >>>> + ret = v4l2_subdev_call(sd, pad, disable_streams, state, pad,
> >>>> + streams_mask);
> >>>> + } else {
> >>>> + /* Stop streaming when the last streams are disabled. */
> >>>> +
> >>>> + if (!(sd->enabled_pads & ~BIT_ULL(pad)))
> >>>> + ret = v4l2_subdev_call(sd, video, s_stream, 0);
> >>>> + else
> >>>> + ret = 0;
> >>>> + }
> >>>> +
> >>>> if (ret) {
> >>>> dev_dbg(dev, "disable streams %u:%#llx failed: %d\n", pad,
> >>>> streams_mask, ret);
> >>>> @@ -2357,10 +2326,12 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
> >>>> v4l2_subdev_set_streams_enabled(sd, state, pad, streams_mask, false);
> >>>>
> >>>> done:
> >>>> - if (!v4l2_subdev_is_streaming(sd))
> >>>> - v4l2_subdev_disable_privacy_led(sd);
> >>>> + if (!use_s_stream) {
> >>>> + if (!v4l2_subdev_is_streaming(sd))
> >>>> + v4l2_subdev_disable_privacy_led(sd);
> >>>
> >>> Do we want to disable the privacy LED on failure in all cases, in
> >>> particular when the .s_stream() or .disable_streams() operations are not
> >>> even called ?
> >>>
> >>> And now that I wrote that, I realize the !v4l2_subdev_is_streaming()
> >>> condition will not be true if the operations failed, so it should be
> >>> fine.
> >>>
> >>> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> >>>
> >>>>
> >>>> - v4l2_subdev_unlock_state(state);
> >>>> + v4l2_subdev_unlock_state(state);
> >>>> + }
> >>>>
> >>>> return ret;
> >>>> }
> >>>>
--
Regards,
Laurent Pinchart
