Re: [PATCH v2 3/7] ACPI: Documentation: Document acpi_dev_state_d0()

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Hi Laurent,

On Sat, Nov 18, 2023 at 08:50:49PM +0200, Laurent Pinchart wrote:
> Hi Sakari,
> 
> Thank you for the patch.
> 
> On Fri, Nov 17, 2023 at 01:14:29PM +0200, Sakari Ailus wrote:
> > Document that acpi_dev_state_d0() can be used to tell if the device was
> > powered on for probe.
> > 
> > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > ---
> >  Documentation/firmware-guide/acpi/non-d0-probe.rst | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/Documentation/firmware-guide/acpi/non-d0-probe.rst b/Documentation/firmware-guide/acpi/non-d0-probe.rst
> > index 7afd16701a02..815bcc8db69f 100644
> > --- a/Documentation/firmware-guide/acpi/non-d0-probe.rst
> > +++ b/Documentation/firmware-guide/acpi/non-d0-probe.rst
> > @@ -24,6 +24,14 @@ there's a problem with the device, the driver likely probes just fine but the
> >  first user will find out the device doesn't work, instead of a failure at probe
> >  time. This feature should thus be used sparingly.
> >  
> > +ACPI framework
> > +--------------
> > +
> > +Use the Linux ACPI framework function :c:func:`acpi_dev_state_d0()` to tell
> > +whether the device was powered on for probe. :c:func:`acpi_dev_state_d0()`
> > +returns true if the device is powered on, false otherwise. For non-ACPI backed
> > +devices it returns true always.
> > +
> 
> While this is true, I don't want to see drivers having to call
> ACPI-specific functions, the same way you dislike OF-specific functions
> in drivers. Please find a better way to handle this.

The functionality is only available on ACPI and the function does the right
thing on non-ACPI platforms. I don't see an issue here.

Feel free to post DT binding patches on suggested device power state during
probe. :-) I think DT would benefit from this as well: the at24 driver is
widely used and suddenly making probe() not talk to the chip (or even power
it up) at all would probably be seen as a regression.

> 
> >  I²C
> >  ---
> >  
> 

-- 
Regards,

Sakari Ailus




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