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SubjectRe: [PATCH 1/3] media: atmel-isc: Not support RBG format from sensor.
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Hi Hans,


On 2017/8/24 14:41, Hans Verkuil wrote:
> On 08/24/2017 08:25 AM, Yang, Wenyou wrote:
>>
>> On 2017/8/23 18:37, Hans Verkuil wrote:
>>> On 08/22/17 09:30, Wenyou.Yang@microchip.com wrote:
>>>> Hi Hans,
>>>>
>>>>> -----Original Message-----
>>>>> From: Hans Verkuil [mailto:hverkuil@xs4all.nl]
>>>>> Sent: 2017年8月22日 15:00
>>>>> To: Wenyou Yang - A41535 <Wenyou.Yang@microchip.com>; Mauro Carvalho
>>>>> Chehab <mchehab@s-opensource.com>
>>>>> Cc: Nicolas Ferre - M43238 <Nicolas.Ferre@microchip.com>; linux-
>>>>> kernel@vger.kernel.org; Sakari Ailus <sakari.ailus@iki.fi>; Jonathan Corbet
>>>>> <corbet@lwn.net>; linux-arm-kernel@lists.infradead.org; Linux Media Mailing List
>>>>> <linux-media@vger.kernel.org>
>>>>> Subject: Re: [PATCH 1/3] media: atmel-isc: Not support RBG format from sensor.
>>>>>
>>>>> On 08/22/2017 03:18 AM, Yang, Wenyou wrote:
>>>>>> Hi Hans,
>>>>>>
>>>>>> On 2017/8/21 22:07, Hans Verkuil wrote:
>>>>>>> On 08/17/2017 09:16 AM, Wenyou Yang wrote:
>>>>>>>> The 12-bit parallel interface supports the Raw Bayer, YCbCr,
>>>>>>>> Monochrome and JPEG Compressed pixel formats from the external
>>>>>>>> sensor, not support RBG pixel format.
>>>>>>>>
>>>>>>>> Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
>>>>>>>> ---
>>>>>>>>
>>>>>>>> drivers/media/platform/atmel/atmel-isc.c | 5 +++++
>>>>>>>> 1 file changed, 5 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/media/platform/atmel/atmel-isc.c
>>>>>>>> b/drivers/media/platform/atmel/atmel-isc.c
>>>>>>>> index d4df3d4ccd85..535bb03783fe 100644
>>>>>>>> --- a/drivers/media/platform/atmel/atmel-isc.c
>>>>>>>> +++ b/drivers/media/platform/atmel/atmel-isc.c
>>>>>>>> @@ -1478,6 +1478,11 @@ static int isc_formats_init(struct isc_device *isc)
>>>>>>>> while (!v4l2_subdev_call(subdev, pad, enum_mbus_code,
>>>>>>>> NULL, &mbus_code)) {
>>>>>>>> mbus_code.index++;
>>>>>>>> +
>>>>>>>> + /* Not support the RGB pixel formats from sensor */
>>>>>>>> + if ((mbus_code.code & 0xf000) == 0x1000)
>>>>>>>> + continue;
>>>>>>> Am I missing something? Here you skip any RGB mediabus formats, but
>>>>>>> in patch 3/3 you add RGB mediabus formats. But this patch prevents
>>>>>>> those new formats from being selected, right?
>>>>>> This patch prevents getting the RGB format from the sensor directly.
>>>>>> The RGB format can be produced by ISC controller by itself.
>>>>> OK, I think I see what is going on here. The isc_formats array really is two arrays
>>>>> in one: up to RAW_FMT_IND_END it describes what it can receive from the
>>>>> source, and after that it describes what it can convert it to.
>>>> Not exactly.
>>>>
>>>> Yes, up to RAW_FMT_IND_END, these formats must be got from the senor, they are RAW formats.
>>>> From ISC_FMT_IND_START to ISC_FMT_IND_END, they can be generated by the ISC controller.
>>>> It is possible they can be got from the sensor too, the driver will check it.
>>>> If it can be got from both the sensor and the ISC controller, the user can use the "sensor_preferred" parameter to decide from which one to get.
>>>> The RBG formats are the exception.
>>>>
>>>>> But if you can't handle RGB formats from the sensor, then why not make sure
>>>>> none of the mbus codes in isc_formats uses RGB? That makes much more sense.
>>>>>
>>>>> E.g.:
>>>>>
>>>>> { V4L2_PIX_FMT_RGB565, MEDIA_BUS_FMT_RGB565_2X8_LE, 16,
>>>>> ISC_PFE_CFG0_BPS_EIGHT, ISC_BAY_CFG_BGBG,
>>>>> ISC_RLP_CFG_MODE_RGB565,
>>>>> ISC_DCFG_IMODE_PACKED16, ISC_DCTRL_DVIEW_PACKED, 0x7b,
>>>>> false, false },
>>>>>
>>>>> Why use MEDIA_BUS_FMT_RGB565_2X8_LE if this apparently is not supported?
>>>> This array is also the lists of all formats supported by the ISC(including got from the sensor).
>>>> The RGB formats are only generated by the ISC controller, not from the sensor.
>>> You're adding code that skips any entries of the table where mbus_code is an
>>> RGB code. But this can also be done by not having RGB mbus codes in the table
>>> in the first place since they make no sense if the HW cannot handle that!
>>> Set the mbus_code to e.g. 0 for such entries, that makes more sense.
>>>
>>> I also strongly suggest changing how the table is organized since those
>>> _FMT_IND_ indices are all to easy to get wrong (and frankly hard to understand).
>> Yes, you are right, I will change it. Do you have some advice?
> Two options spring to mind: split into two tables or add a bool that tells whether
> the format can be created by the isc or not.
I reworked the format table,
http://lists.infradead.org/pipermail/linux-arm-kernel/2017-August/529683.html
Please give your comments.

>
> Regards,
>
> Hans

Best Regards,
Wenyou Yang

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