[U-Boot] [PATCH] dm: core: don't fail to iterate if first one fails to probe

[Rob Clark]

On Thu, Jul 13, 2017 at 3:10 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Rob,
>
> On 21 June 2017 at 04:52, Rob Clark <robdclark at gmail.com> wrote:
>> On Wed, Jun 21, 2017 at 6:23 AM, Peter Robinson <pbrobinson at gmail.com> wrote:
>>> On Tue, Jun 20, 2017 at 10:49 PM, Rob Clark <robdclark at gmail.com> wrote:
>>>> efi_disk_register() would try to iterate all the blk devices.  But if
>>>> the first one in the list failed to probe, uclass_first_device() would
>>>> return NULL and no attempt would be made to register the remaining
>>>> devices.  Also uclass_next_device() needs the same fix.
>>>
>>> This looks related/similar to the "efi_loader: disk: iterate only over
>>> valid block devices" patch [1]
>>>
>>
>> hmm, I don't see uclass_first_device_check() which I guess must be
>> part of another in-flight patch?  I don't mind too much *how* we fix
>> it, as long as it works.  (Although it seems more sensible to just
>> make uclass_first_device()/etc dtrt rather than introducing another
>> function that actually works properly.. but that is only my $0.02)
>
> That patch is now in mainline. It was delayed for a release as I did
> not get any reviews and so wasn't sure if it was needed.
>
> I believe the common case is wanting to stop on error, since it means
> something is wrong. The case of continuing onto another device when
> the first one fails is unusual. We should always check return codes
> and return errors when something is wrong.
>
> I believe this case is happening because the device is removable and
> therefore returns an error. Is that right? If so then we should return
> a single error, such as -ENOMEDIUM so that the caller can ignore that
> error, or consider it OK.

yes, iirc, the first one ended up being sd-card (which was removed)..
I'll have to check if driver is properly returning -ENOMEDIUM.  In
which case maybe the right thing to do is for the iterators skip over
just that single error code, since it isn't really an "unusual" error.

BR,
-R

> In general, though, errors should not be ignored.
>
> Regards,
> Simon
>
> [...]