Re: [PATCH] irqdomain: Add documentation for irq_create_of_mapping()

[Marion & Christophe JAILLET]

Le 18/12/2020 à 19:59, Marc Zyngier a écrit :
> Hi Christophe,
>
> On Tue, 15 Dec 2020 20:07:47 +0000,
> Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> wrote:
> > Add a description for 'irq_create_of_mapping()' and make explicit the fact
> > that the resources allocated by this function can be freed by calling
> > 'irq_dispose_mapping()' when needed (i.e. error handling path, remove
> > function, ...)
> >
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> > The wording can certainly be improved.
> >
> > My goal is only to make clear if patches such as:
> >     https://lore.kernel.org/lkml/20201214202117.146293-1-christophe.jaillet@xxxxxxxxxx/
> > are needed or not.
> > ---
> >   kernel/irq/irqdomain.c | 9 +++++++++
> >   1 file changed, 9 insertions(+)
> >
> > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> > index 6aacd342cd14..d761ece8d43e 100644
> > --- a/kernel/irq/irqdomain.c
> > +++ b/kernel/irq/irqdomain.c
> > @@ -858,6 +858,15 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
> >   }
> >   EXPORT_SYMBOL_GPL(irq_create_fwspec_mapping);
> >   
> > +/**
> > + * irq_create_of_mapping() - Map an interrupt
> I think this deserves a bit more work. My immediate questions when
> reading this are "map where? and to what?".

I won't be of great help here.
I don't know this code enough to be able to provide an accurate description.

> > + * @irq_data: structure of_phandle_args returned by a previous
> > + * of_irq_parse_xxx() call
> That's not strictly true. A of_phandle_args structure can be created
> from scratch (and numerous drivers do that).
>
> > + *
> > + * The resources allocated by this function should be freed by
> > + * calling irq_dispose_mapping() when the mapping if not useful
> > + * anymore.
> This really is a bit of documentation for irq_dispose_mapping(), isn't it?

Well, I don't agree.

I think it is easier to see that some resources need to be freed with a 
dedicated function if it is explained in the description of the function 
which allocates the resource.

CJ

> > + */
> >   unsigned int irq_create_of_mapping(struct of_phandle_args *irq_data)
> >   {
> >   	struct irq_fwspec fwspec;
> Thanks,
>
> 	M.