Re: [PATCH v2 1/2] media: v4l2-cci: Add support for little-endian encoded registers

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Alexander,

Thank you for the patch.

On Wed, Nov 01, 2023 at 01:23:53PM +0100, Alexander Stein wrote:
> Some sensors, e.g. Sony, are using little-endian registers. Add support for

I would write Sony IMX290 here, as there are Sony sensors that use big
endian.

> those by encoding the endianess into Bit 20 of the register address.
> 
> Fixes: af73323b97702 ("media: imx290: Convert to new CCI register access helpers")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---
>  drivers/media/v4l2-core/v4l2-cci.c | 44 ++++++++++++++++++++++++------
>  include/media/v4l2-cci.h           |  5 ++++
>  2 files changed, 41 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-cci.c b/drivers/media/v4l2-core/v4l2-cci.c
> index bc2dbec019b04..673637b67bf67 100644
> --- a/drivers/media/v4l2-core/v4l2-cci.c
> +++ b/drivers/media/v4l2-core/v4l2-cci.c
> @@ -18,6 +18,7 @@
>  
>  int cci_read(struct regmap *map, u32 reg, u64 *val, int *err)
>  {
> +	bool little_endian;
>  	unsigned int len;
>  	u8 buf[8];
>  	int ret;
> @@ -25,6 +26,7 @@ int cci_read(struct regmap *map, u32 reg, u64 *val, int *err)
>  	if (err && *err)
>  		return *err;
>  
> +	little_endian = reg & CCI_REG_LE;

You could initialize the variable when declaring it. Same below.

>  	len = FIELD_GET(CCI_REG_WIDTH_MASK, reg);
>  	reg = FIELD_GET(CCI_REG_ADDR_MASK, reg);
>  
> @@ -40,16 +42,28 @@ int cci_read(struct regmap *map, u32 reg, u64 *val, int *err)
>  		*val = buf[0];
>  		break;
>  	case 2:
> -		*val = get_unaligned_be16(buf);
> +		if (little_endian)
> +			*val = get_unaligned_le16(buf);
> +		else
> +			*val = get_unaligned_be16(buf);

Unrelated to this patch, isn't buf aligned to a 4 bytes boundary ?

>  		break;
>  	case 3:
> -		*val = get_unaligned_be24(buf);
> +		if (little_endian)
> +			*val = get_unaligned_le24(buf);
> +		else
> +			*val = get_unaligned_be24(buf);
>  		break;
>  	case 4:
> -		*val = get_unaligned_be32(buf);
> +		if (little_endian)
> +			*val = get_unaligned_le32(buf);
> +		else
> +			*val = get_unaligned_be32(buf);
>  		break;
>  	case 8:
> -		*val = get_unaligned_be64(buf);
> +		if (little_endian)
> +			*val = get_unaligned_le64(buf);
> +		else
> +			*val = get_unaligned_be64(buf);
>  		break;
>  	default:
>  		dev_err(regmap_get_device(map), "Error invalid reg-width %u for reg 0x%04x\n",
> @@ -68,6 +82,7 @@ EXPORT_SYMBOL_GPL(cci_read);
>  
>  int cci_write(struct regmap *map, u32 reg, u64 val, int *err)
>  {
> +	bool little_endian;
>  	unsigned int len;
>  	u8 buf[8];
>  	int ret;
> @@ -75,6 +90,7 @@ int cci_write(struct regmap *map, u32 reg, u64 val, int *err)
>  	if (err && *err)
>  		return *err;
>  
> +	little_endian = reg & CCI_REG_LE;
>  	len = FIELD_GET(CCI_REG_WIDTH_MASK, reg);
>  	reg = FIELD_GET(CCI_REG_ADDR_MASK, reg);
>  
> @@ -83,16 +99,28 @@ int cci_write(struct regmap *map, u32 reg, u64 val, int *err)
>  		buf[0] = val;
>  		break;
>  	case 2:
> -		put_unaligned_be16(val, buf);
> +		if (little_endian)
> +			put_unaligned_le16(val, buf);
> +		else
> +			put_unaligned_be16(val, buf);
>  		break;
>  	case 3:
> -		put_unaligned_be24(val, buf);
> +		if (little_endian)
> +			put_unaligned_le24(val, buf);
> +		else
> +			put_unaligned_be24(val, buf);
>  		break;
>  	case 4:
> -		put_unaligned_be32(val, buf);
> +		if (little_endian)
> +			put_unaligned_le32(val, buf);
> +		else
> +			put_unaligned_be32(val, buf);
>  		break;
>  	case 8:
> -		put_unaligned_be64(val, buf);
> +		if (little_endian)
> +			put_unaligned_le64(val, buf);
> +		else
> +			put_unaligned_be64(val, buf);
>  		break;
>  	default:
>  		dev_err(regmap_get_device(map), "Error invalid reg-width %u for reg 0x%04x\n",
> diff --git a/include/media/v4l2-cci.h b/include/media/v4l2-cci.h
> index 0f6803e4b17e9..ef3faf0c9d44d 100644
> --- a/include/media/v4l2-cci.h
> +++ b/include/media/v4l2-cci.h
> @@ -32,12 +32,17 @@ struct cci_reg_sequence {
>  #define CCI_REG_ADDR_MASK		GENMASK(15, 0)
>  #define CCI_REG_WIDTH_SHIFT		16
>  #define CCI_REG_WIDTH_MASK		GENMASK(19, 16)
> +#define CCI_REG_LE			BIT(20)
>  
>  #define CCI_REG8(x)			((1 << CCI_REG_WIDTH_SHIFT) | (x))
>  #define CCI_REG16(x)			((2 << CCI_REG_WIDTH_SHIFT) | (x))
>  #define CCI_REG24(x)			((3 << CCI_REG_WIDTH_SHIFT) | (x))
>  #define CCI_REG32(x)			((4 << CCI_REG_WIDTH_SHIFT) | (x))
>  #define CCI_REG64(x)			((8 << CCI_REG_WIDTH_SHIFT) | (x))
> +#define CCI_REG16_LE(x)			((2 << CCI_REG_WIDTH_SHIFT) | (x) | CCI_REG_LE)
> +#define CCI_REG24_LE(x)			((3 << CCI_REG_WIDTH_SHIFT) | (x) | CCI_REG_LE)
> +#define CCI_REG32_LE(x)			((4 << CCI_REG_WIDTH_SHIFT) | (x) | CCI_REG_LE)
> +#define CCI_REG64_LE(x)			((8 << CCI_REG_WIDTH_SHIFT) | (x) | CCI_REG_LE)

I would put CCI_REG_LE first, to match the bits order.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>  
>  /**
>   * cci_read() - Read a value from a single CCI register

-- 
Regards,

Laurent Pinchart