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SubjectRe: [PATCH v5 1/8] drivers: kunit: Generic helpers for test device creation
On 3/23/23 12:27, Greg Kroah-Hartman wrote:
> On Thu, Mar 23, 2023 at 12:01:15PM +0200, Matti Vaittinen wrote:
>> On 3/23/23 10:58, Greg Kroah-Hartman wrote:
>>> On Thu, Mar 23, 2023 at 07:17:40AM +0000, Vaittinen, Matti wrote:
>>>> On 3/22/23 20:57, Greg Kroah-Hartman wrote:
>>>>> On Wed, Mar 22, 2023 at 03:48:00PM +0200, Matti Vaittinen wrote:
>>>>>> Hi Greg,
>>>>>>
>>>>>> Thanks for looking at this.
>>>>>>
>>>>>> On 3/22/23 14:07, Greg Kroah-Hartman wrote:
>>>>>>> On Wed, Mar 22, 2023 at 11:05:55AM +0200, Matti Vaittinen wrote:
>>
>>>>>> The biggest thing for me is that I don't like the idea of creating own 'test
>>>>>> device' in <add subsystem here> while we already have some in DRM (or
>>>>>> others). Thus, I do see value in adding generic helpers for supporting
>>>>>> running KUnit tests on devm_* APIs. Hence it'd be good to have _some_
>>>>>> support for it.
>>>>>
>>>>> I agree, let's use a virtual device and a virtual bus (you can use the
>>>>> auxbus code for this as that's all there for this type of thing)
>>>>
>>>> Hm. The auxiliary_devices require parent. What would be the best way to
>>>> deal with that in KUnit tests?
>>>
>>> If you use NULL as the parent, it goes into the root.
>>
>> As far as I read this is not the case with auxiliary devices. Judging the
>> docs they were intended to be representing some part of a (parent) device. I
>> see the auxiliary_device_init() has explicit check for parent being
>> populated:
>>
>> int auxiliary_device_init(struct auxiliary_device *auxdev)
>> {
>> struct device *dev = &auxdev->dev;
>>
>> if (!dev->parent) {
>> pr_err("auxiliary_device has a NULL dev->parent\n");
>> return -EINVAL;
>> }
>
> Yes as it wants to "split" a device up into smaller devices. So make a
> real device that it can hang off of.

Yep. This is what led me to the root_device_register()... :rolleyes: And
seein the root-device alone could do what I need - adding auxiliary
device on top of it just for the sake of adding one seems a bit of an
over-engineering to me :)

>> As I wrote in another mail, I thought of using a root_device for this IIO
>> test as was suggested by David. To tell the truth, implementing a kunit bus
>> device is starting to feel a bit overwhelming... I started just adding a
>> driver for a light sensor, ended up adding a helper for IIO gain-time-scale
>> conversions and I am slightly reluctant to going the extra-extra mile of
>> adding some UT infrastructure in the context of this driver work...
>
> I think it is worth it as the driver core has no tests. So it obviously
> must be correct, right? :)

Doh. Greg, I hate you :) How could one argue with something like this? I
think I will submit the v6 with the root_device_register() due to the
aux-device requiring it in any case. I know that will end up to your
table still as IIO is going through your hands anyways.

I will however take a look at what Maxime said about devm unwinding not
being done w/o a bus because I think I saw the unwinding done in these
IIO tests even when using the root_device_register()
root_device_unregister(). If the unwinding really is not done, then I
will come back to this auxiliary device rehearsal

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~

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