Re: [PATCH v3 9/9] media: subdev: Support single-stream case in v4l2_subdev_enable/disable_streams()

[Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>]

On 11/04/2024 14:02, Umang Jain wrote:
> Hi Tomi,
>
> On 10/04/24 6:05 pm, 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:
>
> Does this mean the patch needs to be worked upon more ?

I don't see the two issues below as blockers.

> I quickly tested the series by applying it locally with my use case of 
> IMX283 .enable/disable streams and s_stream as the helper function and 
> it seems I am still seeing the same behaviour as before (i.e. not being 
> streamed) and have to carry the workaround as mentioned in [1] **NOTE**

Ok... Then something bugs here, as it is supposed to fix the problem. 
Can you trace the code a bit to see where it goes wrong?

The execution should go to the "if (!(sd->flags & 
V4L2_SUBDEV_FL_STREAMS))" blocks in v4l2_subdev_collect_streams() and 
v4l2_subdev_set_streams_enabled(),

 Tomi

> [1] 
> https://lore.kernel.org/linux-media/20240313070705.91140-1-umang.jain@xxxxxxxxxxxxxxxx/
>
> > - 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.
> >
> > 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 0d376d72ecc7..4a73886741f9 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);
> > +        if (sd->enabled_pads & BIT_ULL(pad))
> > +            *enabled_streams = BIT_ULL(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 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);
> > -    if (!already_streaming)
> > +    if (!use_s_stream && !already_streaming)
> >           v4l2_subdev_enable_privacy_led(sd);
> >   done:
> > -    v4l2_subdev_unlock_state(state);
> > +    if (!use_s_stream)
> > +        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 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);
> > -    v4l2_subdev_unlock_state(state);
> > +        v4l2_subdev_unlock_state(state);
> > +    }
> >       return ret;
> >   }