From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lb1-smtp-cloud7.xs4all.net ([194.109.24.24]:59512 "EHLO lb1-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727177AbeH1OUW (ORCPT ); Tue, 28 Aug 2018 10:20:22 -0400 Subject: Re: [PATCH] media: v4l2-subdev.h: allow V4L2_FRMIVAL_TYPE_CONTINUOUS & _STEPWISE To: Philippe De Muyter Cc: linux-media@vger.kernel.org References: <1535442907-8659-1-git-send-email-phdm@macqel.be> <7bfc83d5-92dd-a604-35a6-4dc659feb7b5@xs4all.nl> <20180828102610.GA31307@frolo.macqel> From: Hans Verkuil Message-ID: Date: Tue, 28 Aug 2018 12:29:21 +0200 MIME-Version: 1.0 In-Reply-To: <20180828102610.GA31307@frolo.macqel> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 28/08/18 12:26, Philippe De Muyter wrote: > Hi Hans, > > On Tue, Aug 28, 2018 at 12:03:25PM +0200, Hans Verkuil wrote: >> Hi Philippe, >> >> On 28/08/18 09:55, Philippe De Muyter wrote: >>> add max_interval and step_interval to struct >>> v4l2_subdev_frame_interval_enum. >> >> Yeah, I never understood why this wasn't supported when this API was designed. >> Clearly an oversight. >> >>> >>> When filled correctly by the sensor driver, those fields must be >>> used as follows by the intermediate level : >>> >>> struct v4l2_frmivalenum *fival; >>> struct v4l2_subdev_frame_interval_enum fie; >>> >>> if (fie.max_interval.numerator == 0) { >>> fival->type = V4L2_FRMIVAL_TYPE_DISCRETE; >>> fival->discrete = fie.interval; >>> } else if (fie.step_interval.numerator == 0) { >>> fival->type = V4L2_FRMIVAL_TYPE_CONTINUOUS; >>> fival->stepwise.min = fie.interval; >>> fival->stepwise.max = fie.max_interval; >>> } else { >>> fival->type = V4L2_FRMIVAL_TYPE_STEPWISE; >>> fival->stepwise.min = fie.interval; >>> fival->stepwise.max = fie.max_interval; >>> fival->stepwise.step = fie.step_interval; >>> } >> >> This is a bit too magical for my tastes. I'd add a type field: >> >> #define V4L2_SUBDEV_FRMIVAL_TYPE_DISCRETE 0 >> #define V4L2_SUBDEV_FRMIVAL_TYPE_CONTINUOUS 1 >> #define V4L2_SUBDEV_FRMIVAL_TYPE_STEPWISE 2 > > Like that ? > > struct v4l2_subdev_frame_interval_enum { > __u32 index; > __u32 pad; > __u32 code; > __u32 width; > __u32 height; > struct v4l2_fract interval; > __u32 which; > __u32 type; > struct v4l2_fract max_interval; > struct v4l2_fract step_interval; > __u32 reserved[3]; > }; Yes. > > >> >> Older applications that do not know about the type field will just >> see a single discrete interval containing the minimum interval. >> I guess that's OK as they will keep working. > > That's actually what also happens with the above implementation, because > max_interval.numerator and step_interval.numerator were previously > reserved and thus 0, and if this code is moved to a helper function, > that does not matter if it's a little bit magical :). It's not just the kernel, but userspace can also enumerate directly from a v4l-subdevX device node, and they can't use any kernel helper functions. Let's keep this API clean. > Both implementations are equal to me, but the proposed one uses less > space from the 'reserved' field. That's OK. Regards, Hans > >> >> While at it: it would be really nice if you can also add stepwise >> support to VIDIOC_SUBDEV_ENUM_FRAME_SIZE. I think the only thing >> you need to do there is to add two new fields: step_width and step_height. >> If 0, then that just means a step size of 1. > > I'll look at that if I find enough interest and test opportunity for it, > but those things are unrelated except that they are missing :) > >> >> Add some helper functions to translate between v4l2_subdev_frame_size/interval_enum >> and v4l2_frmsize/ivalenum and this becomes much cleaner. > > OK > >> >> Regards, >> >> Hans >> >>> >>> Signed-off-by: Philippe De Muyter >>> --- >>> .../uapi/v4l/vidioc-subdev-enum-frame-interval.rst | 39 +++++++++++++++++++++- >>> include/uapi/linux/v4l2-subdev.h | 4 ++- >>> 2 files changed, 41 insertions(+), 2 deletions(-) >>> >>> diff --git a/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst b/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst >>> index 1bfe386..acc516e 100644 >>> --- a/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst >>> +++ b/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst >>> @@ -51,6 +51,37 @@ EINVAL error code if one of the input fields is invalid. All frame >>> intervals are enumerable by beginning at index zero and incrementing by >>> one until ``EINVAL`` is returned. >>> >>> +If the sub-device can work only at the fixed set of frame intervals, >>> +driver must enumerate them with increasing indexes, by only filling >>> +the ``interval`` field. If the sub-device can work with a continuous >>> +range of frame intervals, driver must only return success for index 0 >>> +and fill ``interval`` with the minimum interval, ``max_interval`` with >>> +the maximum interval, and ``step_interval`` with 0 or the step between >>> +the possible intervals. >>> + >>> +Callers are expected to use the returned information as follows : >>> + >>> +.. code-block:: c >>> + >>> + struct v4l2_frmivalenum * fival; >>> + struct v4l2_subdev_frame_interval_enum fie; >>> + >>> + if (fie.max_interval.numerator == 0) { >>> + fival->type = V4L2_FRMIVAL_TYPE_DISCRETE; >>> + fival->discrete = fie.interval; >>> + } else if (fie.step_interval.numerator == 0) { >>> + fival->type = V4L2_FRMIVAL_TYPE_CONTINUOUS; >>> + fival->stepwise.min = fie.interval; >>> + fival->stepwise.max = fie.max_interval; >>> + } else { >>> + fival->type = V4L2_FRMIVAL_TYPE_STEPWISE; >>> + fival->stepwise.min = fie.interval; >>> + fival->stepwise.max = fie.max_interval; >>> + fival->stepwise.step = fie.step_interval; >>> + } >>> + >>> +.. code-block:: c >>> + >>> Available frame intervals may depend on the current 'try' formats at >>> other pads of the sub-device, as well as on the current active links. >>> See :ref:`VIDIOC_SUBDEV_G_FMT` for more >>> @@ -92,8 +123,14 @@ multiple pads of the same sub-device is not defined. >>> - ``which`` >>> - Frame intervals to be enumerated, from enum >>> :ref:`v4l2_subdev_format_whence `. >>> + * - struct :c:type:`v4l2_fract` >>> + - ``max_interval`` >>> + - Maximum period, in seconds, between consecutive video frames, or 0. >>> + * - struct :c:type:`v4l2_fract` >>> + - ``step_interval`` >>> + - Frame interval step size, in seconds, or 0. >>> * - __u32 >>> - - ``reserved``\ [8] >>> + - ``reserved``\ [4] >>> - Reserved for future extensions. Applications and drivers must set >>> the array to zero. >>> >>> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h >>> index 03970ce..c944644 100644 >>> --- a/include/uapi/linux/v4l2-subdev.h >>> +++ b/include/uapi/linux/v4l2-subdev.h >>> @@ -128,7 +128,9 @@ struct v4l2_subdev_frame_interval_enum { >>> __u32 height; >>> struct v4l2_fract interval; >>> __u32 which; >>> - __u32 reserved[8]; >>> + struct v4l2_fract max_interval; >>> + struct v4l2_fract step_interval; >>> + __u32 reserved[4]; >>> }; >>> >>> /** >>> >