[PATCH] dm: make uclass_find_first_device() return error when no defice is found

[Simon Glass]

Hi Masahiro,

On Thu, 27 Feb 2020 at 09:57, Masahiro Yamada <masahiroy at kernel.org> wrote:
>
> Hi Simon,
>
> On Thu, Feb 27, 2020 at 12:33 AM Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi Masahiro,
> >
> > On Mon, 24 Feb 2020 at 23:58, Masahiro Yamada
> > <yamada.masahiro at socionext.com> wrote:
> > >
> > > uclass_find_first_device() succeeds even if it cannot find any device.
> > > So, the caller must check the return code and also *devp is not NULL.
> > >
> > > Returning -ENODEV will be sensible in this case.
> > >
> > > Signed-off-by: Masahiro Yamada <yamada.masahiro at socionext.com>
> > > ---
> > >
> > > If this patch is acceptable, I want to fold this
> > > into my pull request because it need it
> > > for my another patch:
> > > http://patchwork.ozlabs.org/patch/1238000/
> > >
> > >  drivers/core/uclass.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > I sort-of agree and have thought about this a lot.
> >
> > But what are you doing in the case of uclass_find_next_device()?
> >
> > Also what about the tests and other code that expects the current behaviour?
>
>
> OK, I will change my caller side.
>
>
>
> I would probably design these functions as follows:
>
> struct udevice *uclass_find_first_device(enum uclass_id id);
>
> struct udevice *uclass_find_next_device(struct udevice *dev);
>
>
> Return the pointer to the device, or NULL if not found.

I think that is fine, since we don't support any other error than -ENODEV.

I did intend to add checks that the structs are correct (by adding
type information into each struct conditional on a DM_DEBUG option)
and returning a special error when something goes wrong. But even then
I think we could just return NULL and -ENODEV in the caller would be
good enough.

Regards,
Simon