linux-kernel - RE: [PATCH v1 2/8] media: ov2740: Replace voodoo coding with understandle flow

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Message-ID: <DM8PR11MB5653E47793F38ADA5174BFF399979@DM8PR11MB5653.namprd11.prod.outlook.com>
Date:   Wed, 27 Jul 2022 09:52:08 +0000
From:   "Cao, Bingbu" <bingbu.cao@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Qiu, Tian Shu" <tian.shu.qiu@...el.com>,
        "Tu, ShawnX" <shawnx.tu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: RE: [PATCH v1 2/8] media: ov2740: Replace voodoo coding with
 understandle flow

Andy, 

Thanks for your patch.

Although I am not familiar with the voodoo programming, it looks
good for me.

Reviewed-by: Bingbu Cao <bingbu.cao@...el.com>

________________________
BRs,  
Bingbu Cao 

> -----Original Message-----
> From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Sent: Tuesday, July 26, 2022 8:06 PM
> To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>; linux-
> media@...r.kernel.org; linux-kernel@...r.kernel.org
> Cc: Qiu, Tian Shu <tian.shu.qiu@...el.com>; Tu, ShawnX
> <shawnx.tu@...el.com>; Cao, Bingbu <bingbu.cao@...el.com>; Mauro Carvalho
> Chehab <mchehab@...nel.org>
> Subject: [PATCH v1 2/8] media: ov2740: Replace voodoo coding with
> understandle flow
> 
> Besides not being understandable at the first glance, the code might
> provoke a compiler or a static analyser tool to warn about out-of-bound
> access (when len == 0).
> 
> Replace it with clear flow an understandable intention.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/media/i2c/ov2740.c | 28 +++++++++++++++++++++++-----
>  1 file changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov2740.c b/drivers/media/i2c/ov2740.c index
> c975db1bbe8c..81c0ab220339 100644
> --- a/drivers/media/i2c/ov2740.c
> +++ b/drivers/media/i2c/ov2740.c
> @@ -377,10 +377,10 @@ static int ov2740_read_reg(struct ov2740 *ov2740,
> u16 reg, u16 len, u32 *val)
>  	struct i2c_client *client = v4l2_get_subdevdata(&ov2740->sd);
>  	struct i2c_msg msgs[2];
>  	u8 addr_buf[2];
> -	u8 data_buf[4] = {0};
> +	u8 data_buf[4];
>  	int ret = 0;
> 
> -	if (len > sizeof(data_buf))
> +	if (len > 4)
>  		return -EINVAL;
> 
>  	put_unaligned_be16(reg, addr_buf);
> @@ -391,13 +391,22 @@ static int ov2740_read_reg(struct ov2740 *ov2740,
> u16 reg, u16 len, u32 *val)
>  	msgs[1].addr = client->addr;
>  	msgs[1].flags = I2C_M_RD;
>  	msgs[1].len = len;
> -	msgs[1].buf = &data_buf[sizeof(data_buf) - len];
> +	msgs[1].buf = data_buf;
> 
>  	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
>  	if (ret != ARRAY_SIZE(msgs))
>  		return ret < 0 ? ret : -EIO;
> 
> -	*val = get_unaligned_be32(data_buf);
> +	if (len == 4)
> +		*val = get_unaligned_be32(data_buf);
> +	else if (len == 3)
> +		*val = get_unaligned_be24(data_buf);
> +	else if (len == 2)
> +		*val = get_unaligned_be16(data_buf);
> +	else if (len == 1)
> +		*val = data_buf[0];
> +	else
> +		return -EINVAL;
> 
>  	return 0;
>  }
> @@ -412,7 +421,16 @@ static int ov2740_write_reg(struct ov2740 *ov2740,
> u16 reg, u16 len, u32 val)
>  		return -EINVAL;
> 
>  	put_unaligned_be16(reg, buf);
> -	put_unaligned_be32(val << 8 * (4 - len), buf + 2);
> +	if (len == 4)
> +		put_unaligned_be32(val, buf + 2);
> +	else if (len == 3)
> +		put_unaligned_be24(val, buf + 2);
> +	else if (len == 2)
> +		put_unaligned_be16(val, buf + 2);
> +	else if (len == 1)
> +		buf[2] = val;
> +	else
> +		return -EINVAL;
> 
>  	ret = i2c_master_send(client, buf, len + 2);
>  	if (ret != len + 2)
> --
> 2.35.1