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SubjectRe: [PATCH v2 1/5] media: mt9p031: Add support for 8 bit and 10 bit formats
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Hi Laurent,

On 30.09.20 13:42, Laurent Pinchart wrote:
> Hi Stefan,
>
> Thank you for the patch.
>
> On Wed, Sep 30, 2020 at 12:51:29PM +0200, Stefan Riedmueller wrote:
>> From: Christian Hemp <c.hemp@phytec.de>
>>
>> Aside from 12 bit monochrome or color format the sensor implicitly
>> supports 10 and 8 bit formats as well by simply dropping the
>> corresponding LSBs.
>
> That's not how it should work though. If you set the format on
> MEDIA_BUS_FMT_SGRBG8_1X8 through the pipeline for instance, you will end
> up capturing the 8 LSB, not the 8 MSB.
>
> What's your use case for this ?

I use this sensor in combination with an i.MX 6 and i.MX 6UL. When the
sensor is connected with 12 bit (or 10 bit on the i.MX 6UL) and I set
MEDIA_BUS_FMT_SGRBG8_1X8 through the pipeline the CSI interface drops the
unused 4 LSB (or 2 LSB on the i.MX 6UL) so I get the 8 MSB from my 12 bit
sensor.

Does this clarify things? Maybe the description in the commit message is not
accurate enough or did I get something wrong?

Thanks,
Stefan

>
>> Signed-off-by: Christian Hemp <c.hemp@phytec.de>
>> [jlu@pengutronix.de: simplified by dropping v4l2_colorspace handling]
>> Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
>> Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
>> ---
>> Changes in v2:
>> - Use unsigned int for num_fmts and loop variable in find_datafmt
>> - Remove superfluous const qualifier from find_datafmt
>> ---
>> drivers/media/i2c/mt9p031.c | 50 +++++++++++++++++++++++++++++--------
>> 1 file changed, 40 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c
>> index dc23b9ed510a..2e6671ef877c 100644
>> --- a/drivers/media/i2c/mt9p031.c
>> +++ b/drivers/media/i2c/mt9p031.c
>> @@ -116,6 +116,18 @@ enum mt9p031_model {
>> MT9P031_MODEL_MONOCHROME,
>> };
>>
>> +static const u32 mt9p031_color_fmts[] = {
>> + MEDIA_BUS_FMT_SGRBG8_1X8,
>> + MEDIA_BUS_FMT_SGRBG10_1X10,
>> + MEDIA_BUS_FMT_SGRBG12_1X12,
>> +};
>> +
>> +static const u32 mt9p031_monochrome_fmts[] = {
>> + MEDIA_BUS_FMT_Y8_1X8,
>> + MEDIA_BUS_FMT_Y10_1X10,
>> + MEDIA_BUS_FMT_Y12_1X12,
>> +};
>> +
>> struct mt9p031 {
>> struct v4l2_subdev subdev;
>> struct media_pad pad;
>> @@ -138,6 +150,9 @@ struct mt9p031 {
>> struct v4l2_ctrl *blc_auto;
>> struct v4l2_ctrl *blc_offset;
>>
>> + const u32 *fmts;
>> + unsigned int num_fmts;
>> +
>> /* Registers cache */
>> u16 output_control;
>> u16 mode2;
>> @@ -148,6 +163,17 @@ static struct mt9p031 *to_mt9p031(struct v4l2_subdev *sd)
>> return container_of(sd, struct mt9p031, subdev);
>> }
>>
>> +static u32 mt9p031_find_datafmt(struct mt9p031 *mt9p031, u32 code)
>> +{
>> + unsigned int i;
>> +
>> + for (i = 0; i < mt9p031->num_fmts; i++)
>> + if (mt9p031->fmts[i] == code)
>> + return mt9p031->fmts[i];
>> +
>> + return mt9p031->fmts[mt9p031->num_fmts-1];
>> +}
>> +
>> static int mt9p031_read(struct i2c_client *client, u8 reg)
>> {
>> return i2c_smbus_read_word_swapped(client, reg);
>> @@ -476,10 +502,11 @@ static int mt9p031_enum_mbus_code(struct v4l2_subdev *subdev,
>> {
>> struct mt9p031 *mt9p031 = to_mt9p031(subdev);
>>
>> - if (code->pad || code->index)
>> + if (code->pad || code->index >= mt9p031->num_fmts)
>> return -EINVAL;
>>
>> - code->code = mt9p031->format.code;
>> + code->code = mt9p031->fmts[code->index];
>> +
>> return 0;
>> }
>>
>> @@ -573,6 +600,8 @@ static int mt9p031_set_format(struct v4l2_subdev *subdev,
>> __format->width = __crop->width / hratio;
>> __format->height = __crop->height / vratio;
>>
>> + __format->code = mt9p031_find_datafmt(mt9p031, format->format.code);
>> +
>> format->format = *__format;
>>
>> return 0;
>> @@ -951,10 +980,7 @@ static int mt9p031_open(struct v4l2_subdev *subdev, struct v4l2_subdev_fh *fh)
>>
>> format = v4l2_subdev_get_try_format(subdev, fh->pad, 0);
>>
>> - if (mt9p031->model == MT9P031_MODEL_MONOCHROME)
>> - format->code = MEDIA_BUS_FMT_Y12_1X12;
>> - else
>> - format->code = MEDIA_BUS_FMT_SGRBG12_1X12;
>> + format->code = mt9p031_find_datafmt(mt9p031, 0);
>>
>> format->width = MT9P031_WINDOW_WIDTH_DEF;
>> format->height = MT9P031_WINDOW_HEIGHT_DEF;
>> @@ -1121,10 +1147,14 @@ static int mt9p031_probe(struct i2c_client *client,
>> mt9p031->crop.left = MT9P031_COLUMN_START_DEF;
>> mt9p031->crop.top = MT9P031_ROW_START_DEF;
>>
>> - if (mt9p031->model == MT9P031_MODEL_MONOCHROME)
>> - mt9p031->format.code = MEDIA_BUS_FMT_Y12_1X12;
>> - else
>> - mt9p031->format.code = MEDIA_BUS_FMT_SGRBG12_1X12;
>> + if (mt9p031->model == MT9P031_MODEL_MONOCHROME) {
>> + mt9p031->fmts = mt9p031_monochrome_fmts;
>> + mt9p031->num_fmts = ARRAY_SIZE(mt9p031_monochrome_fmts);
>> + } else {
>> + mt9p031->fmts = mt9p031_color_fmts;
>> + mt9p031->num_fmts = ARRAY_SIZE(mt9p031_color_fmts);
>> + }
>> + mt9p031->format.code = mt9p031_find_datafmt(mt9p031, 0);
>>
>> mt9p031->format.width = MT9P031_WINDOW_WIDTH_DEF;
>> mt9p031->format.height = MT9P031_WINDOW_HEIGHT_DEF;
>

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