[U-Boot] [RFC PATCH] dm: ensure device names are unique

[Joe Hershberger]

On Wed, Apr 27, 2016 at 1:40 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 04/26/2016 03:36 PM, Stephen Warren wrote:
>>
>> On 04/26/2016 03:30 PM, Stephen Warren wrote:
>>>
>>> From: Stephen Warren <swarren at nvidia.com>
>>>
>>> It is possible for HW to contain multiple instances of the same
>>> device. In
>>> this case, the name passed to device_bind() may not be unique across all
>>> devices within its uclass. One example is a system with multiple
>>> identical
>>> PCI Ethernet devices. Another might be a system with multiple identical
>>> I2C GPIO expanders, each connected to a separate I2C bus, yet using the
>>> same I2C address on that bus and hence having the same DT node name.
>>>
>>> Enhance the code to detect this situation, and append a sequence
>>> number so
>>> the device name to ensure uniqueness.
>>>
>>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
>>> ---
>>> Some possible issues with this patch:
>>>
>>> 1) Doing this in bind() rather than probe() means dev->seq isn't
>>> available, so can't be used to generate the unique name. This process
>>> should be done during bind() rather than probe() though, since devices
>>> can
>>> be seen (e.g. by running "dm tree") before they're probed. Perhaps the
>>> uclass_resolve_seq() should be called by bind() not probe().
>>>
>>> 2) uclass_find_device_by_name() needs to look up the uclass pointer again
>>> even though device_bind() already knows it.
>>>
>>> 3) Iterating over the list to find the count of devices in the uclass
>>> is a
>>> bit annoying. Should the uclass maintain this count so it doesn't need to
>>> be re-calculated each time?
>>
>>
>> 4) This causes "ut dm autobind" to fail. I'll investigate that locally,
>> but won't bother reposting until the questions above are considered.
>
>
> It looks like that's because I need to add "gd->dm_root && " to the start of
> the following condition:
>
>> @@ -62,6 +62,23 @@ int device_bind(struct udevice *parent, const struct
>> driver *drv,
>>         dev->driver = drv;
>>         dev->uclass = uc;
>>
>> +       if (!uclass_find_device_by_name(uc->uc_drv->id, dev->name, &dev2))
>> {
>
>
> ... otherwise, the uc_class_get/find() nested inside that end up creating a
> second root uclass.

Makes sense.

> I can fold that into v2, pending any other comments.
>
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