Re: [PATCH v2 6/6] media: i2c: ov9282: Fix device detection

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Hi Alexander,

On Fri, Jul 15, 2022 at 09:48:58AM +0200, Alexander Stein wrote:
> Apparently the Vision Components model (VC MIPI OV9281) does not support
> address auto-increment, so probe fails with:
> ov9282 2-0060: chip id mismatch: 9281!=92ff
> Instead do two 1 byte reads and combine the result.
> 
> Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
> ---
> Changes in v2:
> * Fix commit message
> * Add comment about prevented auto-increment
> * Return early if reading ID register failed
> * Reorder ID registers, smaller register number first
> 
>  drivers/media/i2c/ov9282.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> index 263cdffc558f..532791304c3d 100644
> --- a/drivers/media/i2c/ov9282.c
> +++ b/drivers/media/i2c/ov9282.c
> @@ -761,11 +761,24 @@ static int ov9282_set_stream(struct v4l2_subdev *sd, int enable)
>  static int ov9282_detect(struct ov9282 *ov9282)
>  {
>  	int ret;
> +	u32 id[2];
>  	u32 val;
>  
> -	ret = ov9282_read_reg(ov9282, OV9282_REG_ID, 2, &val);
> +	/*
> +	 * Some vendors prevent auto-increment, so each register has to
> +	 * be read separately
> +	 */

I suppose it still works for writes I guess? Would be nice to have this in
the comment.

> +	ret = ov9282_read_reg(ov9282, OV9282_REG_ID,
> +			      1, &id[0]);

Fits on one line. Same below.

>  	if (ret)
>  		return ret;
> +	ret = ov9282_read_reg(ov9282, OV9282_REG_ID + 1,
> +			      1, &id[1]);
> +	if (ret)
> +		return ret;
> +
> +	val = id[1];
> +	val |= (id[0] << 8);
>  
>  	if (val != OV9282_ID) {
>  		dev_err(ov9282->dev, "chip id mismatch: %x!=%x",

-- 
Sakari Ailus



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