[PATCH v6 04/22] of: add function to allow probing a device from a OF node

[Tomeu Vizoso]

On 26 October 2015 at 09:16, Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> On Mon, Sep 21, 2015 at 4:02 PM, Tomeu Vizoso
> <tomeu.vizoso at collabora.com> wrote:
>> Walks the OF tree up and finds the closest ancestor that has a struct
>> device associated with it, probing it if isn't bound to a driver yet.
>>
>> The above should ensure that the dependency represented by the passed OF
>> node is available, because probing a device should cause its descendants
>> to be probed as well (when they get registered).
>>
>> Subsystems can use this when looking up resources for drivers, to reduce
>> the chances of deferred probes because of the probing order of devices.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
>
> Don't know to which response I should post this comment, so I'm responding
> to the original email.
>
> Some subsystems already do this.
> If you call e.g. syscon_regmap_lookup_by_phandle(), it will call
> of_syscon_register() if the syscon device pointed to hasn't been registered yet.

Hi Geert,

I think I prefer if devices are registered as early as possible and
then only probed on-demand, as registration is very much
device-specific but probing is the same for all devices.

But I think in general we should be doing more things on demand and
depending less on the order in which we mass initialize stuff
(devices, classes, drivers, etc).

Regards,

Tomeu

> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
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>                                 -- Linus Torvalds
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