linux-kernel - Re: [PATCH v2 1/5] ACPI: Enable driver and firmware hints to control power at probe time

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Date:   Mon, 26 Aug 2019 13:32:00 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] ACPI: Enable driver and firmware hints to control
 power at probe time

Hi Greg,

On Mon, Aug 26, 2019 at 10:43:43AM +0200, Greg Kroah-Hartman wrote:

...

> > diff --git a/include/linux/device.h b/include/linux/device.h
> > index 6717adee33f01..4bc0ea4a3201a 100644
> > --- a/include/linux/device.h
> > +++ b/include/linux/device.h
> > @@ -248,6 +248,12 @@ enum probe_type {
> >   * @owner:	The module owner.
> >   * @mod_name:	Used for built-in modules.
> >   * @suppress_bind_attrs: Disables bind/unbind via sysfs.
> > + * @probe_low_power: The driver supports its probe function being called while
> > + *		     the device is in a low power state, independently of the
> > + *		     expected behaviour on combination of a given bus and
> > + *		     firmware interface etc. The driver is responsible for
> > + *		     powering the device on using runtime PM in such case.
> > + *		     This configuration has no effect if CONFIG_PM is disabled.
> >   * @probe_type:	Type of the probe (synchronous or asynchronous) to use.
> >   * @of_match_table: The open firmware table.
> >   * @acpi_match_table: The ACPI match table.
> > @@ -285,6 +291,7 @@ struct device_driver {
> >  	const char		*mod_name;	/* used for built-in modules */
> >  
> >  	bool suppress_bind_attrs;	/* disables bind/unbind via sysfs */
> > +	bool probe_low_power;
> 
> Ick, no, this should be a bus-specific thing to handle such messed up
> hardware.  Why polute this in the driver core?

The alternative could be to make it I²C specific indeed; the vast majority
of camera sensors are I²C devices these days.

-- 
Regards,

Sakari Ailus
sakari.ailus@...ux.intel.com