[alsa-devel] [PATCH 000/102] Convert drivers to explicit reset API

[Philipp Zabel]

Hi Thomas,

On Thu, 2017-07-20 at 12:36 +0200, Thomas Petazzoni wrote:
> Hello,
> 
> On Thu, 20 Jul 2017 11:36:55 +0200, Philipp Zabel wrote:
> 
> > > I don't know if it has been discussed in the past, so forgive me if it
> > > has been. Have you considered adding a "int flags" argument to the
> > > existing reset_control_get_*() functions, rather than introducing
> > > separate exclusive variants ?
> > > 
> > > Indeed, with a "int flags" argument you could in the future add more
> > > variants/behaviors without actually multiplying the number of
> > > functions. Something like the "flags" argument for request_irq() for
> > > example.  
> > 
> > I can't find the discussion right now, but I remember we had talked
> > about this in the past.
> > Behind the scenes, all the inline API functions already call common
> > entry points with flags (well, currently separate bool parameters for
> > shared and optional).
> > One reason against exposing those as an int flags in the user facing API
> > is the possibility to accidentally provide a wrong value.
> 
> This is a quite strange argument. You could also accidentally use the
> wrong variant of the function, just like you could use the wrong flag.

You can't accidentally use no flag at all or a completely bogus value
with the "plethora of inline functions" variant.

> Once again, the next time you have another parameter for those reset
> functions, beyond the exclusive/shared variant, you will multiply again
> by two the number of functions ? You already have the  exclusive/shared
> and optional/mandatory variants, so 4 variants. When you'll add a new
> parameter, you'll have 8 variants. Doesn't seem really good.

I'd rather avoid adding more variants, if possible. The complexity
increases regardless of whether the API is expressed as a bunch of
functions or as a single function with a bunch of flags.

> What about reset_control_get(struct device *, const char *, int flags)
> to replace all those variants ?

While I like how this looks, unfortunately (devm_)reset_control_get
already exists without the flags, so we can't change to that with a
gentle transition.

regards
Philipp