[U-Boot] [PATCH v2 1/1] core/uclass: iterate over all devices of a uclass

[Andreas Färber]

Hi Simon,

Am 19.04.2017 um 16:28 schrieb Simon Glass:
> On 19 April 2017 at 05:26, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>> When iterating over the devices of an uclass the iteration stops
>> at the first device that cannot be probed.
>> When calling booefi this will result in no block device being
>> passed to the EFI executable if the first device cannot be probed.
>>
>> The problem was reported by Andreas Färber in
>> https://lists.denx.de/pipermail/u-boot/2017-April/287432.html
>>
>> For testing I used an odroid-c2 with a dts including
>> &sd_emmc_a {
>>         status = "okay";
>> }
>> This device does not exist on the board and cannot be initialized.
>>
>> With the patch uclass_first_device and uclass_next_device
>> iterate internally until they find the first device that can be
>> probed or the end of the device list is reached.
> 
> I would like to avoid changing the API that much. Can you please
> change it to stop calling the tail function and always set the device,
> like you did in v1?

I fear you're missing the key point I made in my lengthy explanation:

Our caller (EFI) wants to iterate over the available devices. SDIO is
not available. If we return a non-NULL device it will try to scan the
disk. Therefore I think v2 is more correct (not yet tested).

So really the question is what your desired semantics of this function
are and how callers here and elsewhere are handling it. If we want to
return non-probed devices to the caller, as you now suggest, then we
would need to audit and amend all callers of the API with some "if
!is_probed() then continue" check. If we simply skip them internally, as
done here IIUC, we require no changes on the caller side, thus much less
invasive.

Maybe we need a new API uclass_{first,next}_available_device() to make
this clear? The change would then only affect callers of the new API,
and EFI and possibly others would again need to be audited and updated.

Regards,
Andreas

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