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Message-ID: <ce4472dc-e414-404d-b3a5-1f736a01504a@collabora.com>
Date: Mon, 15 Jul 2024 15:47:19 +0200
From: Benjamin Gaignard <benjamin.gaignard@...labora.com>
To: Jacopo Mondi <jacopo.mondi@...asonboard.com>
Cc: mchehab@...nel.org, ezequiel@...guardiasur.com.ar,
hverkuil-cisco@...all.nl, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
kernel@...labora.com
Subject: Re: [PATCH v3 1/2] media: videodev2: Add flags to unconditionnaly
enumerate pixels formats
Le 15/07/2024 à 15:37, Jacopo Mondi a écrit :
> Hi Benjamin
>
> On Mon, Jul 15, 2024 at 08:09:55AM GMT, Benjamin Gaignard wrote:
>> Le 12/07/2024 à 18:31, Jacopo Mondi a écrit :
>>> Hi Benjamin
>>>
>>> On Fri, Jul 12, 2024 at 12:29:59PM GMT, Benjamin Gaignard wrote:
>>>> Add new flags to enumerate all pixels formats when calling VIDIOC_ENUM_FMT ioctl.
>>>> When this V4L2_FMT_FLAG_ENUM_ALL_FORMATS flag is set drivers must
>>>> ignore the configuration and return the hardware supported pixel
>>>> formats for the specified queue.
>>>> To distinguish this particular enumeration case V4L2_FMT_FLAG_ALL_FORMATS
>>>> flag must be set by the drivers to highlight support of this feature
>>>> to user space applications.
>>>> This will permit to discover which pixel formats are supported
>>>> without setting codec-specific information so userland can more easily
>>>> know if the driver suits its needs well.
>>>> The main target are stateless decoders so update the documentation
>>>> about how to use this flag.
>>>>
>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>>>> ---
>>>> changes in version 3:
>>>> - Add a flag to inform userspace application that driver
>>>> as take care of the flag.
>>>>
>>>> .../userspace-api/media/v4l/dev-stateless-decoder.rst | 6 ++++++
>>>> .../userspace-api/media/v4l/vidioc-enum-fmt.rst | 9 +++++++++
>>>> .../userspace-api/media/videodev2.h.rst.exceptions | 2 ++
>>>> drivers/media/v4l2-core/v4l2-ioctl.c | 3 +++
>>>> include/uapi/linux/videodev2.h | 2 ++
>>>> 5 files changed, 22 insertions(+)
>>>>
>>>> diff --git a/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst b/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
>>>> index 35ed05f2695e..b0b657de910d 100644
>>>> --- a/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
>>>> +++ b/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
>>>> @@ -58,6 +58,12 @@ Querying capabilities
>>>> default values for these controls being used, and a returned set of formats
>>>> that may not be usable for the media the client is trying to decode.
>>>>
>>>> + * If the ``V4L2_FMT_FLAG_ENUM_ALL_FORMATS`` flag is set the driver must enumerate
>>>> + all the supported formats without taking care of codec-dependent controls
>>>> + set on the ``OUTPUT`` queue. To indicate that the driver has take care of this
>>>> + flag it must set ``V4L2_FMT_FLAG_ALL_FORMATS`` flag for each format while
>>>> + enumerating.
>>>> +
>>>> 3. The client may use :c:func:`VIDIOC_ENUM_FRAMESIZES` to detect supported
>>>> resolutions for a given format, passing desired pixel format in
>>>> :c:type:`v4l2_frmsizeenum`'s ``pixel_format``.
>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>>>> index 3adb3d205531..0399e0fc09b3 100644
>>>> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>>>> @@ -234,6 +234,15 @@ the ``mbus_code`` field is handled differently:
>>>> valid. The buffer consists of ``height`` lines, each having ``width``
>>>> Data Units of data and the offset (in bytes) between the beginning of
>>>> each two consecutive lines is ``bytesperline``.
>>>> + * - ``V4L2_FMT_FLAG_ENUM_ALL_FORMATS``
>>>> + - 0x0400
>>>> + - Set by userland applications to enumerate all possible pixel formats
>>>> + without taking care of any OUTPUT or CAPTURE queue configuration.
>>> This seems to be only relevant for codecs and m2m devices.
>>>
>>> For 'regular' capture (and I presume output) devices isn't the default
>>> behaviour to enumerate all pixel formats, and userspace can decide to
>>> restrict them by providing a media bus code (if the device reports the
>>> V4L2_CAP_IO_MC capability)
>> Yes is targeting codecs because they have two queues.
> Well, m2m devices in general then
>
>> When device have only one queue, like 'regular' capture devices,
>> pixel enumeration doesn't have to take care of the other queue
>> configuration because it doesn't exist.
>>
> This probably needs to be captured in the description here ?
> We already have flags which apply only to some device types, and
> that's specified in the flag description
>
> * - ``V4L2_FMT_FLAG_CSC_QUANTIZATION``
> - 0x0100
> - The driver allows the application to try to change the default
> quantization. This flag is relevant only for capture devices.
That makes sense I will update the flags description in the next version.
Thanks,
Benjamin
>
>>>
>>>> + * - ``V4L2_FMT_FLAG_ALL_FORMATS``
>>>> + - 0x0800
>>>> + - Set by the driver to indicated that format have been enumerated because
>>>> + :ref:`V4L2_FMT_FLAG_ENUM_ALL_FORMATS <v4l2-pix-fmt-flag-set-csc>` has
>>>> + been set by the userland application.
>>>>
>>>> Return Value
>>>> ============
>>>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>> index bdc628e8c1d6..7a3a1e9dc055 100644
>>>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>> @@ -216,6 +216,8 @@ replace define V4L2_FMT_FLAG_CSC_YCBCR_ENC fmtdesc-flags
>>>> replace define V4L2_FMT_FLAG_CSC_HSV_ENC fmtdesc-flags
>>>> replace define V4L2_FMT_FLAG_CSC_QUANTIZATION fmtdesc-flags
>>>> replace define V4L2_FMT_FLAG_META_LINE_BASED fmtdesc-flags
>>>> +replace define V4L2_FMT_FLAG_ENUM_ALL_FORMATS fmtdesc-flags
>>>> +replace define V4L2_FMT_FLAG_ALL_FORMATS fmtdesc-flags
>>>>
>>>> # V4L2 timecode types
>>>> replace define V4L2_TC_TYPE_24FPS timecode-type
>>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>>>> index 4c76d17b4629..5785a98b6ba2 100644
>>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>>> @@ -1569,6 +1569,7 @@ static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
>>>> int ret = check_fmt(file, p->type);
>>>> u32 mbus_code;
>>>> u32 cap_mask;
>>>> + u32 flags;
>>>>
>>>> if (ret)
>>>> return ret;
>>>> @@ -1578,8 +1579,10 @@ static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
>>>> p->mbus_code = 0;
>>>>
>>>> mbus_code = p->mbus_code;
>>>> + flags = p->flags & V4L2_FMT_FLAG_ENUM_ALL_FORMATS;
>>>> memset_after(p, 0, type);
>>>> p->mbus_code = mbus_code;
>>>> + p->flags = flags;
>>>>
>>>> switch (p->type) {
>>>> case V4L2_BUF_TYPE_VIDEO_CAPTURE:
>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>>> index fe6b67e83751..b6a5da79ba21 100644
>>>> --- a/include/uapi/linux/videodev2.h
>>>> +++ b/include/uapi/linux/videodev2.h
>>>> @@ -886,6 +886,8 @@ struct v4l2_fmtdesc {
>>>> #define V4L2_FMT_FLAG_CSC_HSV_ENC V4L2_FMT_FLAG_CSC_YCBCR_ENC
>>>> #define V4L2_FMT_FLAG_CSC_QUANTIZATION 0x0100
>>>> #define V4L2_FMT_FLAG_META_LINE_BASED 0x0200
>>>> +#define V4L2_FMT_FLAG_ENUM_ALL_FORMATS 0x0400
>>>> +#define V4L2_FMT_FLAG_ALL_FORMATS 0x0800
>>>>
>>>> /* Frame Size and frame rate enumeration */
>>>> /*
>>>> --
>>>> 2.43.0
>>>>
>>>>
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