linux-kernel - Re: [PATCH] media: staging: atomisp: improve error handling in gc2235

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Message-ID: <20210524153247.GQ3@paasikivi.fi.intel.com>
Date:   Mon, 24 May 2021 18:32:47 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     trix@...hat.com
Cc:     mchehab@...nel.org, gregkh@...uxfoundation.org,
        hverkuil-cisco@...all.nl, drv@...lo.com,
        martinsdecarvalhobeatriz@...il.com, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: staging: atomisp: improve error handling in
 gc2235_detect()

Hi Tom,

On Fri, May 21, 2021 at 12:48:05PM -0700, trix@...hat.com wrote:
> From: Tom Rix <trix@...hat.com>
> 
> Static analysis reports this representative problem
> 
> atomisp-gc2235.c:867:20: warning: The right operand
>   of '|' is a garbage value
>         id = ((high << 8) | low);
>                           ^ ~~~
> When gc2235_read_reg() fails, its return val is never written.
> 
> For gc2235_detect(), high and low are or-ed and compared
> with GC2235_ID, 0x2235.  Initialize both to 0 and skip
> checking the read returns, it's errors are not passed up, only
> -ENODEV is.
> 
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  drivers/staging/media/atomisp/i2c/atomisp-gc2235.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> index 38defa0f81513..3b6e02b1f45d1 100644
> --- a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> +++ b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> @@ -849,21 +849,14 @@ static int gc2235_get_fmt(struct v4l2_subdev *sd,
>  static int gc2235_detect(struct i2c_client *client)
>  {
>  	struct i2c_adapter *adapter = client->adapter;
> -	u16 high, low;
> -	int ret;
> +	u16 high = 0, low = 0;
>  	u16 id;
>  
>  	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
>  		return -ENODEV;
>  
> -	ret = gc2235_read_reg(client, GC2235_8BIT,
> -			      GC2235_SENSOR_ID_H, &high);
> -	if (ret) {
> -		dev_err(&client->dev, "sensor_id_high = 0x%x\n", high);
> -		return -ENODEV;

It'd be nice if the function returned a different value for different
errors, such as there was an I/O error and that the ID was wrong.

> -	}
> -	ret = gc2235_read_reg(client, GC2235_8BIT,
> -			      GC2235_SENSOR_ID_L, &low);
> +	gc2235_read_reg(client, GC2235_8BIT, GC2235_SENSOR_ID_H, &high);
> +	gc2235_read_reg(client, GC2235_8BIT, GC2235_SENSOR_ID_L, &low);
>  	id = ((high << 8) | low);
>  
>  	if (id != GC2235_ID) {

-- 
Sakari Ailus