linux-kernel - Re: [PATCH v4 33/36] media: imx: redo pixel format enumeration and negotiation

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Message-ID: <9d4fe000-f694-7d3d-34f2-a89cd637b3f0@gmail.com>
Date:   Thu, 23 Feb 2017 17:30:57 -0800
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     robh+dt@...nel.org, mark.rutland@....com, shawnguo@...nel.org,
        kernel@...gutronix.de, fabio.estevam@....com,
        linux@...linux.org.uk, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marIT.de,
        laurent.pinchart+renesas@...asonboard.com, bparrot@...com,
        geert@...ux-m68k.org, arnd@...db.de, sudipm.mukherjee@...il.com,
        minghsiu.tsai@...iatek.com, tiffany.lin@...iatek.com,
        jean-christophe.trotin@...com, horms+renesas@...ge.net.au,
        niklas.soderlund+renesas@...natech.se, robert.jarzmik@...e.fr,
        songjun.wu@...rochip.com, andrew-ct.chen@...iatek.com,
        gregkh@...uxfoundation.org, shuah@...nel.org,
        sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v4 33/36] media: imx: redo pixel format enumeration and
 negotiation



On 02/23/2017 01:10 AM, Philipp Zabel wrote:
> Hi Steve,
>
> On Wed, 2017-02-22 at 15:52 -0800, Steve Longerbeam wrote:
>> Hi Philipp,
>>
>>
>> On 02/16/2017 03:32 AM, Philipp Zabel wrote:
>>> On Wed, 2017-02-15 at 18:19 -0800, Steve Longerbeam wrote:
>>>> The previous API and negotiation of mbus codes and pixel formats
>>>> was broken, and has been completely redone.
>>>>
>>>> The negotiation of media bus codes should be as follows:
>>>>
>>>> CSI:
>>>>
>>>> sink pad     direct src pad      IDMAC src pad
>>>> --------     ----------------    -------------
>>>> RGB (any)        IPU RGB           RGB (any)
>>>> YUV (any)        IPU YUV           YUV (any)
>>>> Bayer              N/A             must be same bayer code as sink
>>>
>>> The IDMAC src pad should also use the internal 32-bit RGB / YUV format,
>>> except if bayer/raw mode is selected, in which case the attached capture
>>> video device should only allow a single mode corresponding to the output
>>> pad media bus format.
>>
>> The IDMAC source pad is going to memory, so it has left the IPU.
>> Are you sure it should be an internal IPU format? I realize it
>> is linked to a capture device node, and the IPU format could then
>> be translated to a v4l2 fourcc by the capture device, but IMHO this
>> pad is external to the IPU.
>
> The CSI IDMAC source pad should describe the format at the connection
> between the CSI and the IDMAC, just as the icprpvf and icprpenc source
> pads.
> The format outside of the IPU is the memory format written by the IDMAC,
> but that is a memory pixel format and not a media bus format at all.
>

True, it is a memory format. I don't really mind if the CSI and PRP
ENC/VF source pads are characterized as IPU internal formats, since
they are only used to indicate the colorspace to the capture device.

And yes it did simplify the enumeration and try_fmt code a bit. So
I went ahead and made the change.

Steve


> That would also make it more straightforward to enumerate the memory
> pixel formats in the capture device: If the source pad media bus format
> is 32-bit YUV, enumerate all YUV formats, if it is 32-bit RGB or RGB565,
> enumerate all rgb formats, otherwise (bayer/raw mode) only allow the
> specific memory format matching the bus format.
>
>