Re: [PATCH 5/8] iio: accel: kx022a: Switch to sparse friendly iio_device_claim/release_direct()

[David Lechner <dlechner@baylibre.com>]

On 2/19/25 6:21 AM, Matti Vaittinen wrote:
> On 19/02/2025 12:51, Nuno Sá wrote:
>> On Wed, 2025-02-19 at 07:36 +0200, Matti Vaittinen wrote:
>>> On 18/02/2025 17:42, David Lechner wrote:
>>>> On 2/18/25 1:39 AM, Matti Vaittinen wrote:
>>>>> On 17/02/2025 16:01, Jonathan Cameron wrote:
>>>>>> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>>>>>
>>>>>> These new functions allow sparse to find failures to release
>>>>>> direct mode reducing chances of bugs over the claim_direct_mode()
>>>>>> functions that are deprecated.
>>>>>>
>>>>>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>>>>> Cc: Matti Vaittinen <mazziesaccount@gmail.com>
>>>>>> ---
>>>>>>     drivers/iio/accel/kionix-kx022a.c | 14 ++++++--------
>>>>>>     1 file changed, 6 insertions(+), 8 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/iio/accel/kionix-kx022a.c
>>>>>> b/drivers/iio/accel/kionix-kx022a.c
>>>>>> index 727e007c5fc1..07dcf5f0599f 100644
>>>>>> --- a/drivers/iio/accel/kionix-kx022a.c
>>>>>> +++ b/drivers/iio/accel/kionix-kx022a.c
>>>>>> @@ -577,13 +577,12 @@ static int kx022a_write_raw(struct iio_dev *idev,
>>>>>>          * issues if users trust the watermark to be reached within known
>>>>>>          * time-limit).
>>>>>>          */
>>>>>> -    ret = iio_device_claim_direct_mode(idev);
>>>>>> -    if (ret)
>>>>>> -        return ret;
>>>>>> +    if (!iio_device_claim_direct(idev))
>>>>>> +        return -EBUSY;
>>>>>
>>>>> Not really in the scope of this review - but in my opinion the logic of
>>>>> this check is terribly counter intuitive. I mean,
>>>>>
>>>>>> +    if (iio_device_claim_direct(idev))
>>>>>> +        return -EBUSY;
>>>>
>>>> I'm curious how you read this then. I read this as:
>>>>
>>>> "If claiming direct mode succeeded, then return an error!"
>>>
>>> I am used to seeing a pattern where function returning zero indicates a
>>> success. I have no statistics but I believe this is true for a vast
>>> majority of functions in the kernel. I believe this was the case with
>>> the old 'iio_device_claim_direct_mode(idev)' too.
>>>
>>
>> Fair enough... Note though this is returning a boolean where true makes total
>> sense for the "good" case. I do agree it's not super clear just by reading the
>> code that the API is supposed to return a boolean.
> 
> Exactly. Just seeing the call in code was not obvious to me. It required finding the prototype to understand what happens.
> 
> Anyways, I guess this discussion is out of the scope of this patch and if no one else sees this important enough to go and change the iio_device_claim_direct() - then I am fine with this patch. So, with a bit of teeth grinding:
> 
> Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
> 
> Yours,
>   -- Matti
> 
> 

Would a name like iio_device_try_claim_direct_mode() make it more
obvious that it returned a bool instead of int?