linux-kernel - RE: [PATCH v1 1/1] media: i2c: imx290: Make use of get_unaligned_le24(), put_unaligned

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Date:   Wed, 8 Feb 2023 22:49:53 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Manivannan Sadhasivam <mani@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: RE: [PATCH v1 1/1] media: i2c: imx290: Make use of
 get_unaligned_le24(), put_unaligned_le24()

From: Andy Shevchenko
> Sent: 08 February 2023 11:30
> 
> Since we have a proper endianness converters for LE 24-bit data use
> them. While at it, format the code using switch-cases as it's done
> for the rest of the endianness handlers.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/media/i2c/imx290.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
> index 49d6c8bdec41..330098a0772d 100644
> --- a/drivers/media/i2c/imx290.c
> +++ b/drivers/media/i2c/imx290.c
> @@ -16,6 +16,9 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
> +
> +#include <asm/unaligned.h>
> +
>  #include <media/media-entity.h>
>  #include <media/v4l2-ctrls.h>
>  #include <media/v4l2-device.h>
> @@ -466,18 +469,20 @@ static int __always_unused imx290_read(struct imx290 *imx290, u32 addr, u32 *val
>  		return ret;
>  	}
> 
> -	*value = (data[2] << 16) | (data[1] << 8) | data[0];
> +	*value = get_unaligned_le24(data);
>  	return 0;
>  }
> 
>  static int imx290_write(struct imx290 *imx290, u32 addr, u32 value, int *err)
>  {
> -	u8 data[3] = { value & 0xff, (value >> 8) & 0xff, value >> 16 };
> +	u8 data[3];
>  	int ret;
> 
>  	if (err && *err)
>  		return *err;
> 
> +	put_unaligned_le24(value, data);
> +
>  	ret = regmap_raw_write(imx290->regmap, addr & IMX290_REG_ADDR_MASK,
>  			       data, (addr >> IMX290_REG_SIZE_SHIFT) & 3);

Why not just use an le32, htole32() and take the address of the low byte?

Anything doing put/get on a 24bit value is pretty much required
to do byte accesses anyway.

	David

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