linux-kernel - Re: [PATCH] counter: add defaults to switch-statements

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Message-ID: <fc462e60-9a33-39a4-a0be-b6331923be74@redhat.com>
Date:   Mon, 28 Feb 2022 05:18:51 -0800
From:   Tom Rix <trix@...hat.com>
To:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     nathan@...nel.org, ndesaulniers@...gle.com,
        Jonathan.Cameron@...wei.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] counter: add defaults to switch-statements


On 2/28/22 5:03 AM, William Breathitt Gray wrote:
> On Sun, Feb 27, 2022 at 05:46:10PM +0000, Jonathan Cameron wrote:
>> On Sun, 27 Feb 2022 08:17:46 -0800
>> trix@...hat.com wrote:
>>
>>> From: Tom Rix <trix@...hat.com>
>>>
>>> Clang static analysis reports this representative problem
>>> counter-chrdev.c:482:3: warning: Undefined or garbage value
>>>    returned to caller
>>>    return ret;
>>>    ^~~~~~~~~~
>>>
>>> counter_get_data() has a multilevel switches, some without
>>> defaults, so ret is sometimes not set.
>>> Add returning -EINVAL similar to other defaults.
>>>
>>> Fixes: b6c50affda59 ("counter: Add character device interface")
>>> Signed-off-by: Tom Rix <trix@...hat.com>
>> I'm fairly sure this one is warning supression rather than a fix as
>> that type u8 being used in the switch is storing an enum which is
>> set only by kernel code and all values of the enum are covered.
>>
>> However, that's not locally visible so to me the addition looks good, I'd
>> just be tempted to drop the fixes tag as backporting this looks like noise
>> to me.
>>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Yes, this isn't really a bug because the only values available are those
> from the enum, but I see how this is not immediately obvious at first.
> If Tom has no objections, I'll pick this up and drop the fixes tag so
> that we have it along with the other counter changes for the 5.18 merge.

Sounds good.

Thanks,

Tom

> Thanks,
>
> William Breathitt Gray
>
>>> ---
>>>   drivers/counter/counter-chrdev.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c
>>> index b7c62f957a6a8..69d340be9c93f 100644
>>> --- a/drivers/counter/counter-chrdev.c
>>> +++ b/drivers/counter/counter-chrdev.c
>>> @@ -477,6 +477,8 @@ static int counter_get_data(struct counter_device *const counter,
>>>   		case COUNTER_SCOPE_COUNT:
>>>   			ret = comp->count_u8_read(counter, parent, &value_u8);
>>>   			break;
>>> +		default:
>>> +			return -EINVAL;
>>>   		}
>>>   		*value = value_u8;
>>>   		return ret;
>>> @@ -496,6 +498,8 @@ static int counter_get_data(struct counter_device *const counter,
>>>   		case COUNTER_SCOPE_COUNT:
>>>   			ret = comp->count_u32_read(counter, parent, &value_u32);
>>>   			break;
>>> +		default:
>>> +			return -EINVAL;
>>>   		}
>>>   		*value = value_u32;
>>>   		return ret;