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

[Simon Glass]

Hi Heinrih,

On 19 April 2017 at 09:55, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> On 04/19/2017 04:28 PM, Simon Glass wrote:
>> Hi Heinrich,
>>
>> 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?
>
> Hello Simon,
>
> with the patch nothing changes if the the available devices an
> contiguous starting at index 0.
>
> Not calling the tail function would really change the API function in
> all cases. So why would we want to do so?
>
> The current behavior is to stop at the first device that cannot be
> probed. Which use of uclass_first_device/uclass_next_device do you see
> in the U-Boot code that would benefit from this?
>>
>> Also don't forget to add a test for this bahaviour. You may need to
>> have sandbox device that returns an error when probing. Perhaps add
>> another compatible string to denx,u-boot-fdt-test?
>
> I will give it a try.

See my follow-up replies. I don't think we should change that
function, actually.

>
> Best regards
>
> Heinrich
>
>>
>>>
>>> Debug output is provided for the two functions.
>>>
>>> Reported-by: Andreas Färber <afaerber at suse.de>
>>> Cc: Simon Glass <sjg at chromium.org>
>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>> ---
>>> v2:
>>>   As suggested by Simon Glass correct uclass_first_device() and
>>>   uclass_next_device() instead of uclass_get_device_tail() to
>>>   avoid side effects.
>>> v1:
>>>   The original patch was posted as
>>>   core/uclass: uclass_get_device_tail: always set devp
>>>   https://lists.denx.de/pipermail/u-boot/2017-April/288068.html
>>> ---
>>>  drivers/core/uclass.c | 44 +++++++++++++++++++++++++++++++++-----------
>>>  1 file changed, 33 insertions(+), 11 deletions(-)
>>>
>>
>> Regards,
>> Simon
>>
>