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Subject: Re: [PATCH] media: ov7670: check status of ov7670_read
To:     Sakari Ailus <sakari.ailus@iki.fi>
Cc:     corbet@lwn.net, mchehab@kernel.org, natechancellor@gmail.com,
        ndesaulniers@google.com, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20200828145518.26324-1-trix@redhat.com>
 <20201006124148.GC5682@valkosipuli.retiisi.org.uk>
From:   Tom Rix <trix@redhat.com>
Message-ID: <75462c9b-afc0-aeb7-018a-573db59192f4@redhat.com>
Date:   Tue, 6 Oct 2020 07:17:10 -0700
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On 10/6/20 5:41 AM, Sakari Ailus wrote:
> Hi Tom,
>
> On Fri, Aug 28, 2020 at 07:55:18AM -0700, trix@redhat.com wrote:
>> From: Tom Rix <trix@redhat.com>
>>
>> clang static analysis flags this representative problem
>>
>> drivers/media/i2c/ov7670.c:1463:9: warning: Assigned
>>   value is garbage or undefined
>>         *value = gain;
>>                ^ ~~~~
>>
>> gain is set by a successful call to ov7670_read()
>>
>> So check that ov7670_read() is successful.
>>
>> The remaining static analysis problems are false positives.
>> There appears to be a limitation with checking the
>> aggregated returns.
>>
>> Signed-off-by: Tom Rix <trix@redhat.com>
>> ---
>>  drivers/media/i2c/ov7670.c | 17 +++++++++++++----
>>  1 file changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/i2c/ov7670.c b/drivers/media/i2c/ov7670.c
>> index b42b289faaef..001d4b09db72 100644
>> --- a/drivers/media/i2c/ov7670.c
>> +++ b/drivers/media/i2c/ov7670.c
>> @@ -929,6 +929,8 @@ static int ov7670_set_hw(struct v4l2_subdev *sd, int hstart, int hstop,
>>  	ret =  ov7670_write(sd, REG_HSTART, (hstart >> 3) & 0xff);
>>  	ret += ov7670_write(sd, REG_HSTOP, (hstop >> 3) & 0xff);
>>  	ret += ov7670_read(sd, REG_HREF, &v);
>> +	if (ret)
>> +		return ret;
> Thanks for the patch.
>
> While the patch fixes a bug, could you also fix adding the return values?
> These are valid error codes to begin with, but it makes no sense to add
> them together.

Yes. That is a problem, a general problem with this file.

I count 10+

I'll see if fixing the general problem also fixes this problem.

Tom

>
>>  	v = (v & 0xc0) | ((hstop & 0x7) << 3) | (hstart & 0x7);
>>  	msleep(10);
>>  	ret += ov7670_write(sd, REG_HREF, v);
>> @@ -938,6 +940,8 @@ static int ov7670_set_hw(struct v4l2_subdev *sd, int hstart, int hstop,
>>  	ret += ov7670_write(sd, REG_VSTART, (vstart >> 2) & 0xff);
>>  	ret += ov7670_write(sd, REG_VSTOP, (vstop >> 2) & 0xff);
>>  	ret += ov7670_read(sd, REG_VREF, &v);
>> +	if (ret)
>> +		return ret;
>>  	v = (v & 0xf0) | ((vstop & 0x3) << 2) | (vstart & 0x3);
>>  	msleep(10);
>>  	ret += ov7670_write(sd, REG_VREF, v);
>> @@ -1460,6 +1464,8 @@ static int ov7670_g_gain(struct v4l2_subdev *sd, __s32 *value)
>>  	unsigned char gain;
>>  
>>  	ret = ov7670_read(sd, REG_GAIN, &gain);
>> +	if (ret)
>> +		return ret;
>>  	*value = gain;
>>  	return ret;
>>  }
>> @@ -1470,11 +1476,14 @@ static int ov7670_s_gain(struct v4l2_subdev *sd, int value)
>>  	unsigned char com8;
>>  
>>  	ret = ov7670_write(sd, REG_GAIN, value & 0xff);
>> +	if (ret)
>> +		return ret;
>>  	/* Have to turn off AGC as well */
>> -	if (ret == 0) {
>> -		ret = ov7670_read(sd, REG_COM8, &com8);
>> -		ret = ov7670_write(sd, REG_COM8, com8 & ~COM8_AGC);
>> -	}
>> +	ret = ov7670_read(sd, REG_COM8, &com8);
>> +	if (ret)
>> +		return ret;
>> +	ret = ov7670_write(sd, REG_COM8, com8 & ~COM8_AGC);
>> +
>>  	return ret;
>>  }
>>