From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Cc: kieran.bingham@ideasonboard.com, Lee Jones <lee.jones@linaro.org>,
Vladimir Zapolskiy <vz@mleia.com>,
Linus Walleij <linus.walleij@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Marek Vasut <marek.vasut@gmail.com>,
Wolfram Sang <wsa@the-dreams.de>,
devicetree@vger.kernel.org, linux-gpio@vger.kernel.org,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/7] mfd: ds90ux9xx: add TI DS90Ux9xx de-/serializer MFD driver
Date: Tue, 16 Oct 2018 16:12:02 +0300 [thread overview]
Message-ID: <6392366.NPbusjoGUK@avalon> (raw)
In-Reply-To: <369ef3ac-6f68-c450-713f-762b1c5cd5c9@mentor.com>
Hi Vladimir,
On Saturday, 13 October 2018 18:10:25 EEST Vladimir Zapolskiy wrote:
> On 10/12/2018 04:01 PM, Laurent Pinchart wrote:
> > On Friday, 12 October 2018 14:47:52 EEST Kieran Bingham wrote:
> >> On 12/10/18 11:58, Vladimir Zapolskiy wrote:
> [snip]
>
> >> Essentially they are multi purpose buses - which do not yet have a home.
> >> We have used media as a home because of our use case.
> >>
> >> The use case whether they transfer frames from a camera or to a display
> >> are of course closely related, but ultimately covered by two separate
> >> subsystems at the pixel level (DRM vs V4L, or other for other data)
> >>
> >> Perhaps as they are buses - on a level with USB or I2C (except they can
> >> of course carry I2C or Serial as well as 'bi-directional video' etc ),
> >> they are looking for their own subsystem.
> >>
> >> Except I don't think we don't want to add a new subsystem for just one
> >> (or two) devices...
> >
> > I'm not sure a new subsystem is needed. As you've noted there's an overlap
> > between drivers/media/ and drivers/gpu/drm/ in terms of supported
> > hardware. We even have a devices supported by two drivers, one in drivers/
> > media/ and one in drivers/gpu/drm/ (I'm thinking about the adv7511 in
> > particular). This is a well known issue, and so far nothing has been done
> > in mainline to try and solve it.
>
> I agree that there's an overlap between drivers/media/ and drivers/gpu/drm/,
> formally a hypothetical (sic!) DS90Ux9xx video bridge cell driver should be
> added into both subsystems also, and the actual driver of two should be
> selected in runtime. I call such a driver 'hypothetical', because in fact I
> don't have it, and I'm not so sure that its existence is justified, but
> that's only because DS90Ux9xx video bridge functionality is _transparent_,
> it does not have any controls literally, but it is a pure luck eventually.
I don't think that's entirely correct, there's at least the video bus width
(18-bit/24-bit) that needs to be selected. You currently do so through a
pinctrl property, but that's not right.
> So, as I've stated in my cover letter, I can misuse yours 'lvds-encoder'
> driver only for the purpose of establishing a mediated link between
> an LVDS controller and a panel over a serializer-deserializer pair.
>
> > Trying to find another home in drivers/mfd/ to escape from the problem
> > isn't a good solution in my opinion. The best option from a Linux point
> > of view would be to unify V4L2 and DRM/KMS when it comes to bridge
> > support, but that's a long way down the road (I won't complain if you
> > want to give it a go though>
> > :-)).
>
> I return you a wider smile :)
>
> > As your use cases are display, focused, I would propose to start with
> > drivers/gpu/drm/bridge/, and leave the problem of camera support for first
> > person who will have such a use case.
>
> Frankly speaking I would like to start from copy-pasting your 'lvds-encoder'
> driver into an 'absolutely-transparent-video-bridge' driver with no LVDS or
> 'encoder' specifics, adding just a new compatible may suffice, if the
> driver is renamed/redefined.
>
> PS, I remember I owe you a reference OF snippet of data path to a panel.
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2018-10-16 13:11 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-08 21:11 [PATCH 0/7] mfd/pinctrl: add initial support of TI DS90Ux9xx ICs Vladimir Zapolskiy
2018-10-08 21:11 ` [PATCH 1/7] dt-bindings: mfd: ds90ux9xx: add description " Vladimir Zapolskiy
2018-10-09 0:13 ` Marek Vasut
2018-10-09 11:11 ` Vladimir Zapolskiy
2018-10-09 20:55 ` Vladimir Zapolskiy
2018-10-09 21:03 ` Marek Vasut
2018-10-10 8:41 ` Linus Walleij
2018-10-12 11:44 ` Laurent Pinchart
2018-10-13 14:28 ` Vladimir Zapolskiy
2018-10-16 12:30 ` Laurent Pinchart
2018-10-30 16:43 ` Luca Ceresoli
2018-10-30 23:40 ` Vladimir Zapolskiy
2018-10-08 21:12 ` [PATCH 2/7] dt-bindings: mfd: ds90ux9xx: add description of TI DS90Ux9xx I2C bridge Vladimir Zapolskiy
2018-10-12 11:54 ` Laurent Pinchart
2018-10-30 16:43 ` Luca Ceresoli
2018-10-31 20:12 ` Vladimir Zapolskiy
2018-11-03 21:00 ` Luca Ceresoli
2018-11-03 22:07 ` Vladimir Zapolskiy
2018-10-08 21:12 ` [PATCH 3/7] dt-bindings: pinctrl: ds90ux9xx: add description of TI DS90Ux9xx pinmux Vladimir Zapolskiy
2018-10-10 8:45 ` Linus Walleij
2018-10-17 15:02 ` Rob Herring
2018-10-12 12:01 ` Laurent Pinchart
2018-10-13 13:47 ` Vladimir Zapolskiy
2018-10-16 12:48 ` Laurent Pinchart
2018-10-30 16:44 ` Luca Ceresoli
2018-10-31 20:31 ` Vladimir Zapolskiy
2018-10-08 21:12 ` [PATCH 4/7] mfd: ds90ux9xx: add TI DS90Ux9xx de-/serializer MFD driver Vladimir Zapolskiy
2018-10-09 4:08 ` kbuild test robot
2018-10-09 11:14 ` Vladimir Zapolskiy
2018-10-12 6:03 ` Lee Jones
2018-10-12 7:41 ` Vladimir Zapolskiy
2018-10-12 8:39 ` Lee Jones
2018-10-12 9:20 ` Kieran Bingham
2018-10-12 10:58 ` Vladimir Zapolskiy
2018-10-12 11:34 ` Lee Jones
2018-10-12 14:13 ` Vladimir Zapolskiy
2018-10-12 14:25 ` Lee Jones
2018-10-12 11:47 ` Kieran Bingham
2018-10-12 13:01 ` Laurent Pinchart
2018-10-12 13:59 ` Vladimir Zapolskiy
2018-10-16 13:08 ` Laurent Pinchart
2018-10-23 8:16 ` Vladimir Zapolskiy
2018-10-30 16:44 ` Luca Ceresoli
2018-10-13 15:10 ` Vladimir Zapolskiy
2018-10-16 13:12 ` Laurent Pinchart [this message]
2018-10-16 18:32 ` Vladimir Zapolskiy
2018-10-13 12:33 ` Vladimir Zapolskiy
2018-10-12 11:24 ` Vladimir Zapolskiy
2018-10-12 11:43 ` Lee Jones
2018-10-12 14:23 ` Vladimir Zapolskiy
2018-10-12 13:07 ` Laurent Pinchart
2018-10-08 21:12 ` [PATCH 5/7] mfd: ds90ux9xx: add I2C bridge/alias and link connection driver Vladimir Zapolskiy
2018-10-12 6:04 ` Lee Jones
2018-10-12 7:32 ` Vladimir Zapolskiy
2018-10-12 9:03 ` Lee Jones
2018-10-12 13:12 ` Laurent Pinchart
2018-10-12 14:36 ` Vladimir Zapolskiy
2018-10-16 14:06 ` Laurent Pinchart
2018-10-08 21:12 ` [PATCH 6/7] pinctrl: ds90ux9xx: add TI DS90Ux9xx pinmux and GPIO controller driver Vladimir Zapolskiy
2018-10-10 9:04 ` Linus Walleij
2018-10-08 21:12 ` [PATCH 7/7] MAINTAINERS: add entry for TI DS90Ux9xx FPD-Link III drivers Vladimir Zapolskiy
2018-10-12 11:34 ` [PATCH 0/7] mfd/pinctrl: add initial support of TI DS90Ux9xx ICs Laurent Pinchart
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