From: mchehab@s-opensource•com (Mauro Carvalho Chehab)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit controls from a pipeline
Date: Sat, 11 Mar 2017 10:14:08 -0300 [thread overview]
Message-ID: <20170311101408.272a9187@vento.lan> (raw)
In-Reply-To: <5e1183f4-774f-413a-628a-96e0df321faf@xs4all.nl>
Em Sat, 11 Mar 2017 12:32:43 +0100
Hans Verkuil <hverkuil@xs4all•nl> escreveu:
> On 10/03/17 16:09, Mauro Carvalho Chehab wrote:
> > Em Fri, 10 Mar 2017 13:54:28 +0100
> > Hans Verkuil <hverkuil@xs4all•nl> escreveu:
> >
> >>> Devices that have complex pipeline that do essentially require using the
> >>> Media controller interface to configure them are out of that scope.
> >>>
> >>
> >> Way too much of how the MC devices should be used is in the minds of developers.
> >> There is a major lack for good detailed documentation, utilities, compliance
> >> test (really needed!) and libv4l plugins.
> >
> > Unfortunately, we merged an incomplete MC support at the Kernel. We knew
> > all the problems with MC-based drivers and V4L2 applications by the time
> > it was developed, and we requested Nokia developers (with was sponsoring MC
> > develoment, on that time) to work on a solution to allow standard V4L2
> > applications to work with MC based boards.
> >
> > Unfortunately, we took the decision to merge MC without that, because
> > Nokia was giving up on Linux development, and we didn't want to lose the
> > 2 years of discussions and work around it, as Nokia employers were leaving
> > the company. Also, on that time, there was already some patches floating
> > around adding backward support via libv4l. Unfortunately, those patches
> > were never finished.
> >
> > The net result is that MC was merged with some huge gaps, including
> > the lack of a proper solution for a generic V4L2 program to work
> > with V4L2 devices that use the subdev API.
> >
> > That was not that bad by then, as MC was used only on cell phones
> > that run custom-made applications.
> >
> > The reallity changed, as now, we have lots of low cost SoC based
> > boards, used for all sort of purposes. So, we need a quick solution
> > for it.
> >
> > In other words, while that would be acceptable support special apps
> > on really embedded systems, it is *not OK* for general purpose SoC
> > harware[1].
> >
> > [1] I'm calling "general purpose SoC harware" those ARM boards
> > like Raspberry Pi that are shipped to the mass and used by a wide
> > range of hobbyists and other people that just wants to run Linux on
> > ARM. It is possible to buy such boards for a very cheap price,
> > making them to be used not only on special projects, where a custom
> > made application could be interesting, but also for a lot of
> > users that just want to run Linux on a low cost ARM board, while
> > keeping using standard V4L2 apps, like "camorama".
> >
> > That's perhaps one of the reasons why it took a long time for us to
> > start receiving drivers upstream for such hardware: it is quite
> > intimidating and not logical to require developers to implement
> > on their drivers 2 complex APIs (MC, subdev) for those
> > hardware that most users won't care. From user's perspective,
> > being able to support generic applications like "camorama" and
> > "zbar" is all they want.
> >
> > In summary, I'm pretty sure we need to support standard V4L2
> > applications on boards like Raspberry Pi and those low-cost
> > SoC-based boards that are shipped to end users.
> >
> >> Anyway, regarding this specific patch and for this MC-aware driver: no, you
> >> shouldn't inherit controls from subdevs. It defeats the purpose.
> >
> > Sorry, but I don't agree with that. The subdev API is an optional API
> > (and even the MC API can be optional).
> >
> > I see the rationale for using MC and subdev APIs on cell phones,
> > ISV and other embedded hardware, as it will allow fine-tuning
> > the driver's support to allow providing the required quality for
> > certain custom-made applications. but on general SoC hardware,
> > supporting standard V4L2 applications is a need.
> >
> > Ok, perhaps supporting both subdev API and V4L2 API at the same
> > time doesn't make much sense. We could disable one in favor of the
> > other, either at compilation time or at runtime.
>
> Right. If the subdev API is disabled, then you have to inherit the subdev
> controls in the bridge driver (how else would you be able to access them?).
> And that's the usual case.
>
> If you do have the subdev API enabled, AND you use the MC, then the
> intention clearly is to give userspace full control and inheriting controls
> no longer makes any sense (and is highly confusing IMHO).
I tend to agree with that.
> >
> > This way, if the subdev API is disabled, the driver will be
> > functional for V4L2-based applications that don't support neither
> > MC or subdev APIs.
>
> I'm not sure if it makes sense for the i.MX driver to behave differently
> depending on whether the subdev API is enabled or disabled. I don't know
> enough of the hardware to tell if it would ever make sense to disable the
> subdev API.
Yeah, I don't know enough about it either. The point is: this is
something that the driver maintainer and driver users should
decide if it either makes sense or not, based on the expected use cases.
Thanks,
Mauro
next prev parent reply other threads:[~2017-03-11 13:14 UTC|newest]
Thread overview: 228+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-16 2:19 [PATCH v4 00/36] i.MX Media Driver Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 01/36] [media] dt-bindings: Add bindings for i.MX media driver Steve Longerbeam
2017-02-16 11:54 ` Philipp Zabel
2017-02-16 19:20 ` Steve Longerbeam
2017-02-27 14:38 ` Rob Herring
2017-03-01 0:00 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 02/36] ARM: dts: imx6qdl: Add compatible, clocks, irqs to MIPI CSI-2 node Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 03/36] ARM: dts: imx6qdl: Add mipi_ipu1/2 multiplexers, mipi_csi, and their connections Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 04/36] ARM: dts: imx6qdl: add capture-subsystem device Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 05/36] ARM: dts: imx6qdl-sabrelite: remove erratum ERR006687 workaround Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 06/36] ARM: dts: imx6-sabrelite: add OV5642 and OV5640 camera sensors Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 07/36] ARM: dts: imx6-sabresd: " Steve Longerbeam
2017-02-17 0:51 ` Fabio Estevam
2017-02-17 0:56 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 08/36] ARM: dts: imx6-sabreauto: create i2cmux for i2c3 Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 09/36] ARM: dts: imx6-sabreauto: add reset-gpios property for max7310_b Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 10/36] ARM: dts: imx6-sabreauto: add pinctrl for gpt input capture Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 11/36] ARM: dts: imx6-sabreauto: add the ADV7180 video decoder Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 12/36] add mux and video interface bridge entity functions Steve Longerbeam
2017-02-19 21:28 ` Pavel Machek
2017-02-22 17:19 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 13/36] [media] v4l2: add a frame timeout event Steve Longerbeam
2017-03-02 15:53 ` Sakari Ailus
2017-03-02 23:07 ` Steve Longerbeam
2017-03-03 11:45 ` Sakari Ailus
2017-03-03 22:43 ` Steve Longerbeam
2017-03-04 10:56 ` Sakari Ailus
2017-03-05 0:37 ` Steve Longerbeam
2017-03-05 21:31 ` Sakari Ailus
2017-03-05 22:41 ` Russell King - ARM Linux
2017-03-10 2:38 ` Steve Longerbeam
2017-03-10 9:33 ` Russell King - ARM Linux
2017-02-16 2:19 ` [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit controls from a pipeline Steve Longerbeam
2017-02-19 21:44 ` Pavel Machek
2017-03-02 16:02 ` Sakari Ailus
2017-03-02 23:48 ` Steve Longerbeam
2017-03-03 0:46 ` Steve Longerbeam
2017-03-03 2:12 ` Steve Longerbeam
2017-03-03 19:17 ` Sakari Ailus
2017-03-03 22:47 ` Steve Longerbeam
2017-03-03 23:06 ` Russell King - ARM Linux
2017-03-04 0:36 ` Steve Longerbeam
2017-03-04 13:13 ` Sakari Ailus
2017-03-10 12:54 ` Hans Verkuil
2017-03-10 13:07 ` Russell King - ARM Linux
2017-03-10 13:22 ` Hans Verkuil
2017-03-10 14:01 ` Russell King - ARM Linux
2017-03-10 14:20 ` Hans Verkuil
2017-03-10 15:53 ` Mauro Carvalho Chehab
2017-03-10 22:37 ` Sakari Ailus
2017-03-11 11:25 ` Mauro Carvalho Chehab
2017-03-11 21:52 ` Pavel Machek
2017-03-11 23:14 ` Russell King - ARM Linux
2017-03-12 0:19 ` Steve Longerbeam
2017-03-12 21:29 ` Pavel Machek
2017-03-12 22:37 ` Mauro Carvalho Chehab
2017-03-14 18:26 ` Pavel Machek
2017-03-13 12:46 ` Sakari Ailus
2017-03-14 3:45 ` Mauro Carvalho Chehab
2017-03-14 7:55 ` Hans Verkuil
2017-03-14 10:21 ` Mauro Carvalho Chehab
2017-03-14 22:32 ` media / v4l2-mc: wishlist for complex cameras (was Re: [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit controls from a pipeline) Pavel Machek
2017-03-15 0:54 ` Mauro Carvalho Chehab
2017-03-15 10:50 ` Philippe De Muyter
2017-03-15 18:55 ` Nicolas Dufresne
2017-03-16 9:26 ` Philipp Zabel
2017-03-16 9:47 ` Philippe De Muyter
2017-03-16 10:01 ` Philipp Zabel
2017-03-16 10:19 ` Philippe De Muyter
2017-03-15 18:04 ` Pavel Machek
2017-03-15 20:26 ` Mauro Carvalho Chehab
2017-03-16 22:11 ` Pavel Machek
2017-03-20 13:24 ` [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit controls from a pipeline Hans Verkuil
2017-03-20 15:39 ` Mauro Carvalho Chehab
2017-03-20 16:10 ` Russell King - ARM Linux
2017-03-20 17:37 ` Mauro Carvalho Chehab
2017-03-17 11:42 ` Russell King - ARM Linux
2017-03-17 11:55 ` Sakari Ailus
2017-03-17 13:24 ` Mauro Carvalho Chehab
2017-03-17 13:51 ` Philipp Zabel
2017-03-17 14:37 ` Russell King - ARM Linux
2017-03-20 13:10 ` Hans Verkuil
2017-03-20 15:06 ` Mauro Carvalho Chehab
2017-03-21 11:11 ` Pavel Machek
2017-03-20 11:16 ` Hans Verkuil
2017-03-17 12:02 ` Philipp Zabel
2017-03-17 12:16 ` Russell King - ARM Linux
2017-03-17 17:49 ` Mauro Carvalho Chehab
2017-03-19 13:25 ` Pavel Machek
2017-03-26 16:44 ` Laurent Pinchart
2017-03-10 15:26 ` Mauro Carvalho Chehab
2017-03-10 15:57 ` Russell King - ARM Linux
2017-03-10 17:06 ` Russell King - ARM Linux
2017-03-10 20:42 ` Mauro Carvalho Chehab
2017-03-10 21:55 ` Pavel Machek
2017-03-10 15:09 ` Mauro Carvalho Chehab
2017-03-11 11:32 ` Hans Verkuil
2017-03-11 13:14 ` Mauro Carvalho Chehab [this message]
2017-03-11 15:32 ` Sakari Ailus
2017-03-11 17:32 ` Russell King - ARM Linux
2017-03-11 18:08 ` Steve Longerbeam
2017-03-11 18:45 ` Russell King - ARM Linux
2017-03-11 18:54 ` Steve Longerbeam
2017-03-11 18:59 ` Russell King - ARM Linux
2017-03-11 19:06 ` Steve Longerbeam
2017-03-11 20:41 ` Russell King - ARM Linux
2017-03-12 3:31 ` Steve Longerbeam
2017-03-12 7:37 ` Russell King - ARM Linux
2017-03-12 17:56 ` Steve Longerbeam
2017-03-12 21:58 ` Mauro Carvalho Chehab
2017-03-26 9:12 ` script to setup pipeline was " Pavel Machek
2017-03-13 10:44 ` Hans Verkuil
2017-03-13 10:58 ` Russell King - ARM Linux
2017-03-13 11:08 ` Hans Verkuil
2017-03-13 11:42 ` Mauro Carvalho Chehab
2017-03-13 12:35 ` Russell King - ARM Linux
2017-03-12 18:14 ` Pavel Machek
2017-03-11 20:26 ` Pavel Machek
2017-03-11 20:33 ` Steve Longerbeam
2017-03-11 21:30 ` Pavel Machek
2017-02-16 2:19 ` [PATCH v4 15/36] platform: add video-multiplexer subdevice driver Steve Longerbeam
2017-02-19 22:02 ` Pavel Machek
2017-02-21 9:11 ` Philipp Zabel
2017-02-24 20:09 ` Pavel Machek
2017-02-27 14:41 ` Rob Herring
2017-03-01 0:20 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 16/36] UAPI: Add media UAPI Kbuild file Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 17/36] media: Add userspace header file for i.MX Steve Longerbeam
2017-02-16 11:33 ` Philipp Zabel
2017-02-22 23:54 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 18/36] media: Add i.MX media core driver Steve Longerbeam
2017-02-16 10:27 ` Russell King - ARM Linux
2017-02-16 17:53 ` Steve Longerbeam
2017-02-16 13:02 ` Philipp Zabel
2017-02-16 13:44 ` Russell King - ARM Linux
2017-02-17 1:33 ` Steve Longerbeam
2017-02-17 8:34 ` Philipp Zabel
2017-02-16 2:19 ` [PATCH v4 19/36] media: imx: Add Capture Device Interface Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 20/36] media: imx: Add CSI subdev driver Steve Longerbeam
2017-02-16 11:52 ` Russell King - ARM Linux
2017-02-16 12:40 ` Russell King - ARM Linux
2017-02-16 13:09 ` Russell King - ARM Linux
2017-02-16 14:20 ` Russell King - ARM Linux
2017-02-16 19:07 ` Steve Longerbeam
2017-02-16 18:44 ` Steve Longerbeam
2017-02-16 19:09 ` Russell King - ARM Linux
2017-02-16 2:19 ` [PATCH v4 21/36] media: imx: Add VDIC " Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 22/36] media: imx: Add IC subdev drivers Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev driver Steve Longerbeam
2017-02-16 10:28 ` Russell King - ARM Linux
2017-02-16 17:54 ` Steve Longerbeam
2017-02-17 10:47 ` Philipp Zabel
2017-02-17 11:06 ` Russell King - ARM Linux
2017-02-17 11:38 ` Philipp Zabel
2017-02-22 23:38 ` Steve Longerbeam
2017-02-22 23:41 ` Steve Longerbeam
2017-02-23 0:06 ` Steve Longerbeam
2017-02-23 0:09 ` Steve Longerbeam
2017-02-17 14:16 ` Philipp Zabel
2017-02-17 18:27 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 24/36] [media] add Omnivision OV5640 sensor driver Steve Longerbeam
2017-02-27 14:45 ` Rob Herring
2017-03-01 0:43 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 25/36] ARM: imx_v6_v7_defconfig: Enable staging video4linux drivers Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 26/36] media: imx: add support for bayer formats Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 27/36] media: imx: csi: " Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 28/36] media: imx: csi: fix crop rectangle changes in set_fmt Steve Longerbeam
2017-02-16 11:05 ` Russell King - ARM Linux
2017-02-16 18:16 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and getting of frame rates Steve Longerbeam
2017-02-18 1:11 ` Steve Longerbeam
2017-02-18 1:12 ` Steve Longerbeam
2017-02-18 9:23 ` Russell King - ARM Linux
2017-02-18 17:29 ` Steve Longerbeam
2017-02-18 18:08 ` Russell King - ARM Linux
2017-02-20 22:04 ` Sakari Ailus
2017-02-20 22:56 ` Steve Longerbeam
2017-02-20 23:47 ` Steve Longerbeam
2017-02-21 12:15 ` Sakari Ailus
2017-02-21 22:21 ` Steve Longerbeam
2017-02-21 23:34 ` Steve Longerbeam
2017-02-21 0:13 ` Russell King - ARM Linux
2017-02-21 0:18 ` Steve Longerbeam
2017-02-21 8:50 ` Philipp Zabel
2017-03-13 13:16 ` Sakari Ailus
2017-03-13 13:27 ` Russell King - ARM Linux
2017-03-13 13:55 ` Philipp Zabel
2017-03-13 18:06 ` Steve Longerbeam
2017-03-13 21:03 ` Sakari Ailus
2017-03-13 21:29 ` Russell King - ARM Linux
2017-03-14 7:34 ` Hans Verkuil
2017-03-14 10:43 ` Philipp Zabel
2017-03-13 20:56 ` Sakari Ailus
2017-03-13 21:07 ` Russell King - ARM Linux
2017-02-21 12:37 ` Sakari Ailus
2017-02-21 13:21 ` Russell King - ARM Linux
2017-02-21 15:38 ` Sakari Ailus
2017-02-21 16:03 ` Russell King - ARM Linux
2017-02-21 16:15 ` Sakari Ailus
2017-02-16 2:19 ` [PATCH v4 30/36] media: imx: update capture dev format on IDMAC output pad set_fmt Steve Longerbeam
2017-02-16 11:29 ` Philipp Zabel
2017-02-16 2:19 ` [PATCH v4 31/36] media: imx: csi: add __csi_get_fmt Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 32/36] media: imx: csi/fim: add support for frame intervals Steve Longerbeam
2017-02-16 2:38 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 33/36] media: imx: redo pixel format enumeration and negotiation Steve Longerbeam
2017-02-16 11:32 ` Philipp Zabel
2017-02-22 23:52 ` Steve Longerbeam
2017-02-23 9:10 ` Philipp Zabel
2017-02-24 1:30 ` Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 34/36] media: imx: csi: add frame skipping support Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 35/36] media: imx: csi: fix crop rectangle reset in sink set_fmt Steve Longerbeam
2017-02-16 2:19 ` [PATCH v4 36/36] media: imx: propagate sink pad formats to source pads Steve Longerbeam
2017-02-16 11:29 ` Philipp Zabel
2017-02-16 18:19 ` Steve Longerbeam
2017-02-16 11:37 ` [PATCH v4 00/36] i.MX Media Driver Russell King - ARM Linux
2017-02-16 18:30 ` Steve Longerbeam
2017-02-16 22:20 ` Russell King - ARM Linux
2017-02-16 22:27 ` Steve Longerbeam
2017-02-16 22:57 ` Russell King - ARM Linux
2017-02-17 10:39 ` Philipp Zabel
2017-02-17 10:56 ` Russell King - ARM Linux
2017-02-17 11:21 ` Philipp Zabel
2017-02-18 17:21 ` Steve Longerbeam
2017-02-17 11:43 ` Philipp Zabel
2017-02-17 12:22 ` Sakari Ailus
2017-02-17 12:31 ` Russell King - ARM Linux
2017-02-17 15:04 ` Philipp Zabel
2017-02-18 11:58 ` Sakari Ailus
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