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Date: Thu, 4 Apr 2024 16:47:41 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>, Hans Verkuil
<hverkuil@...all.nl>, Umang Jain <umang.jain@...asonboard.com>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] media: subdev: Improve
v4l2_subdev_enable/disable_streams_fallback
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@...asonboard.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)?
Tomi
>
> 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;
>>>> };
>>>>
>
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