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Message-ID: <72940e89-0384-4fd3-8a10-42d6db44fdf0@ideasonboard.com>
Date: Thu, 11 Apr 2024 14:07:34 +0300
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Subject: Re: [PATCH v3 9/9] media: subdev: Support single-stream case in
 v4l2_subdev_enable/disable_streams()
To: Umang Jain <umang.jain@ideasonboard.com>
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
 Mauro Carvalho Chehab <mchehab@kernel.org>, Hans Verkuil
 <hverkuil@xs4all.nl>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
 Sakari Ailus <sakari.ailus@linux.intel.com>
References: <20240410-enable-streams-impro-v3-0-e5e7a5da7420@ideasonboard.com>
 <20240410-enable-streams-impro-v3-9-e5e7a5da7420@ideasonboard.com>
 <f8e293b7-6a06-4477-9c7e-d1b83163f8e1@ideasonboard.com>
Content-Language: en-US
From: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Autocrypt: addr=tomi.valkeinen@ideasonboard.com; keydata=
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In-Reply-To: <f8e293b7-6a06-4477-9c7e-d1b83163f8e1@ideasonboard.com>
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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@ideasonboard.com/
> 
>>
>> - 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@ideasonboard.com>
>> ---
>>   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;
>>   }
>>
>