Re: [PATCH v1 0/2] iio: core: remove iio_validate_own_trigger() function

[Vasileios Amoiridis <vassilisamir@gmail.com>]

On Sat, Sep 28, 2024 at 03:55:19PM +0100, Jonathan Cameron wrote:
> On Sun, 22 Sep 2024 13:07:21 +0200
> Vasileios Amoiridis <vassilisamir@gmail.com> wrote:
> 
> > On Sun, Sep 22, 2024 at 12:44:15PM +0300, Matti Vaittinen wrote:
> > > On 9/21/24 23:07, Vasileios Amoiridis wrote:  
> > > > On Sat, Sep 21, 2024 at 12:23:39PM -0700, Lars-Peter Clausen wrote:  
> > > > > On 9/21/24 11:19, Vasileios Amoiridis wrote:  
> > > > > > The iio_validate_own_trigger() function was added in this commit [1] but it is
> > > > > > the same with the below function called iio_trigger_validate_own_device(). The
> > > > > > bodies of the functions can be found in [2], [3].
> > > > > > 
> > > > > > [1]: https://lore.kernel.org/all/51cd3e3e74a6addf8d333f4a109fb9c5a11086ee.1683541225.git.mazziesaccount@gmail.com/
> > > > > > [2]: https://elixir.bootlin.com/linux/v6.11/source/drivers/iio/industrialio-trigger.c#L732
> > > > > > [3]: https://elixir.bootlin.com/linux/v6.11/source/drivers/iio/industrialio-trigger.c#L752  
> > > > > 
> > > > > The signature of the two functions are different, the order of the
> > > > > parameters is switched. So you can't just swap them out for the
> > > > > `validate_trigger` callback since the signature is not compatible. But maybe
> > > > > you can update the implementation of one of the functions to calling the
> > > > > other function.
> > > > >   
> > > > 
> > > > Hi Lars,
> > > > 
> > > > Hmm, I see what you mean. Still though, do you think that we could do some
> > > > cleaning here? I can see 3 approaches:
> > > > 
> > > > 1) One of the 2 functions calls the other internally and nothing else has
> > > > to change.  
> > > 
> > > I would go with this. Changing the signatures to be the same would be (in
> > > my, not always humble enough, opinion) wrong. The different order of
> > > parameters reflects the different idea. One checks if device for trigger is
> > > the right one, the other checks if the trigger for the device is the right
> > > one. Thus, the order of parameters should be different.
> > > 
> > > Calling the same implementation internally is fine with me. Maybe Jonathan
> > > will share his opinion when recovers from all the plumbing in Vienna ;)
> > > 
> > > Yours,
> > > 	-- Matti
> > > 
> > > -- 
> > > Matti Vaittinen
> > > Linux kernel developer at ROHM Semiconductors
> > > Oulu Finland
> > >   
> > 
> > Hi Matti!
> > 
> > Thanks for your comment! Well, I still think in my eyes is better to
> > have one function do one thing instead of multiple. Also, I didn't
> > think of this argument with the order of arguments, it makes sense.
> > My experience is quite limited to how things should be in such a
> > large project so I trust your opinion. I would still like to see
> > what Jonathan has to say on this though, maybe he had some
> > reasoning behind!!!
> > 
> No to changing the signatures. It removes the difference
> in meaning of the callbacks even though they happen to have
> the same implementation in this very simple (and common case).
> 
> In the trigger first one, that is the subject.  We are asking the
> question 'is this trigger ok being used for this device'.
> In the other the device is the subject and we asking the
> question 'is this device ok to use this trigger'
> 
> When we are checking the combination you have here, sure they
> become the same thing but there are devices where it
> matters that the trigger is not used to drive other devices
> (typically because it's a hardware line that goes nowhere
> else, so no interrupts etc) but other triggers can be used
> to drive this device (often by software triggering the scan).
> We have the opposite case as well but that's often
> a shortcut when it just happens to be really complex to get
> the trigger to reset (often requires reading all the data
> or similar) - that condition can almost always be relaxed
> but sometimes it's a lot of code for a niche case.
> 
> So fine to change the implementation of one of these
> checks on tightly coupled device and trigger to call the other
> but don't touch the callback signatures as to that breaks the
> logical parameter ordering.
> 
> Jonathan
> 

Hi Jonathan,

Thank you very much for the explanation, it makes total sense.
No need to change everything I think, it is a very small thing
and maybe even better like how it is now from what I understand.

Cheers,
Vasilis

> > Have a nice day!
> > 
> > Cheers,
> > Vasilis
>