Re: [PATCH 02/10] driver: consult feature controller prior to device probe

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Philipp,

On 18.08.22 10:19, Philipp Zabel wrote:
> Hi Ahmad,
> 
> On Do, 2022-08-18 at 07:19 +0200, Ahmad Fatoum wrote:
>> The newly added feature controller framework has two goals: Avoid
>> probing device in barebox that aren't indeed available
> 
> This specific wording makes me wonder why this isn't implemented inside
> of_device_is_available().
> 
> This would also take care of other devices querying device node
> availability, for example via of_graph_port_is_available(), if that
> ever happens.

I admit that restricting the barebox-side of feature controllers to device
probe can be limiting. For kernel fixup, any node may be disabled, unlike
with barebox, where only device probes can be skipped.

Placing the feature controller check in of_device_is_available is not
trivial. We currently do a single pass through the device tree and create
devices that are of_device_is_available(). If we start to look up the
feature controller there, we will need to do device creation in multiple
passes. While of_probe() can be called multiple times, I think there are
quite a few cornercase we will need to take into consideration when
doing this and are thus better addressed separately when the need arises.

Thanks,
Ahmad

> 
> regards
> Philipp
> 


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