Re: [PATCH v7 09/15] media: bcm2835-unicam: Add support for CCP2/CSI2 camera interface

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Cc: linux-media@vger.kernel.org,
	Dave Stevenson <dave.stevenson@raspberrypi.com>,
	David Plowman <david.plowman@raspberrypi.com>,
	Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	Naushir Patuck <naush@raspberrypi.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	kernel-list@raspberrypi.com,
	linux-rpi-kernel@lists.infradead.org,
	Florian Fainelli <florian.fainelli@broadcom.com>,
	Ray Jui <rjui@broadcom.com>,
	Scott Branden <sbranden@broadcom.com>,
	bcm-kernel-feedback-list@broadcom.com,
	Conor Dooley <conor+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v7 09/15] media: bcm2835-unicam: Add support for CCP2/CSI2 camera interface
Date: Tue, 2 Apr 2024 09:05:07 +0300	[thread overview]
Message-ID: <20240402060507.GA4703@pendragon.ideasonboard.com> (raw)
In-Reply-To: <cdcf9848-eee9-44a7-b033-315b1514740d@ideasonboard.com>

On Tue, Apr 02, 2024 at 09:00:43AM +0300, Tomi Valkeinen wrote:
> On 01/04/2024 16:52, Laurent Pinchart wrote:
> > On Wed, Mar 27, 2024 at 01:21:09PM +0200, Tomi Valkeinen wrote:
> >> On 25/03/2024 00:08, Laurent Pinchart wrote:
> >>> From: Dave Stevenson <dave.stevenson@raspberrypi.com>
> >>>
> >>> Add a driver for the Unicam camera receiver block on BCM283x processors.
> >>> It is represented as two video device nodes: unicam-image and
> >>> unicam-embedded which are connected to an internal subdev (named
> >>> unicam-subdev) in order to manage streams routing.
> >>
> >> Shouldn't this driver call get_frame_desc somewhere to get the VC and DT
> >> for the streams?
> > 
> > Generally speaking, yes. In practice, configuring the DT from the frame
> > descriptor is probably not very useful, as CSI-2 sources that transmit
> > image data using a DT that doesn't correspond to the media bus code are
> > not very common and I don't expect this to be needed for unicam.
> 
> Perhaps, but if the driver gets the DT from the frame descriptor, then 
> the driver doesn't need to have tables for the DTs.
> 
> Although when I did this with the RPi CFE driver, I also implemented a 
> fallback mechanism for the cases when there is no get_frame_desc, and so 
> I still had to keep the DT tables...

I did the same in v9. The DT value in the existing format info table
also serves for CCP2 support, which isn't supported by
.get_frame_desc(). Even if it was, CCP2 doesn't have an explicit DT
concept (as far as I can tell), but the hardware requires the DT value
to still be programmed.

-- 
Regards,

Laurent Pinchart