linux-kernel - RE: [RESEND v3 2/3] media: qcom: venus: Fix uninitialized variable warning

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Message-ID:
 <SL2P216MB1246B8100FF5853ACD68F8EDFB972@SL2P216MB1246.KORP216.PROD.OUTLOOK.COM>
Date: Fri, 30 Aug 2024 04:26:13 +0000
From: Nas Chung <nas.chung@...psnmedia.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>, "mchehab@...nel.org"
	<mchehab@...nel.org>, "hverkuil@...all.nl" <hverkuil@...all.nl>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RESEND v3 2/3] media: qcom: venus: Fix uninitialized variable
 warning

Hi, Bryan O'Donoghue.

I received feedback from Hans with detailed information about this error.
https://lore.kernel.org/linux-kernel/a962e94f-a669-40e1-8b28-9ef077cf69be@xs4all.nl/

And, you may face the following error message using the smatch and the sparse test.
"find_format_by_index() error: uninitialized symbol 'valid'."

"make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- -j8 M=drivers/media/platform/qcom/venus C=2 CHECK=smatch"

Or, linux-kernel build with "-Wmaybe-uninitialized" gcc option.
"make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- -j8 M=drivers/media/platform/qcom/venus KCFLAGS="-Wmaybe-uninitialized"

>-----Original Message-----
>From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>Sent: Thursday, August 29, 2024 7:31 PM
>To: Nas Chung <nas.chung@...psnmedia.com>; mchehab@...nel.org;
>hverkuil@...all.nl; linux-media@...r.kernel.org
>Cc: linux-kernel@...r.kernel.org
>Subject: Re: [RESEND v3 2/3] media: qcom: venus: Fix uninitialized
>variable warning
>
>On 25/07/2024 07:10, Nas Chung wrote:
>> Avoid uninitialized variable when both V4L2_TYPE_IS_OUTPUT() and
>> V4L2_TYPE_IS_CAPTURE() return false.
>>
>> Signed-off-by: Nas Chung <nas.chung@...psnmedia.com>
>> ---
>>   drivers/media/platform/qcom/venus/vdec.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/vdec.c
>b/drivers/media/platform/qcom/venus/vdec.c
>> index d12089370d91..b72b579018e3 100644
>> --- a/drivers/media/platform/qcom/venus/vdec.c
>> +++ b/drivers/media/platform/qcom/venus/vdec.c
>> @@ -161,7 +161,7 @@ find_format_by_index(struct venus_inst *inst,
>unsigned int index, u32 type)
>>
>>   		if (V4L2_TYPE_IS_OUTPUT(type)) {
>>   			valid = venus_helper_check_codec(inst, fmt[i].pixfmt);
>> -		} else if (V4L2_TYPE_IS_CAPTURE(type)) {
>> +		} else {
>>   			valid = venus_helper_check_format(inst, fmt[i].pixfmt);
>>
>>   			if (fmt[i].pixfmt == V4L2_PIX_FMT_QC10C &&
>
>Can you give an example of the error - compile time I assume, this fixes ?
>
>---
>bod