linux-kernel - Re: [PATCH 7/7] OF/ACPI/I2C: Add generic match function for the aforementioned systems

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Message-ID: <20140604125141.GB5214@lahna.fi.intel.com>
Date:	Wed, 4 Jun 2014 15:51:41 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Lee Jones <lee.jones@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	wsa@...-dreams.de, grant.likely@...aro.org,
	linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
	linus.walleij@...aro.org
Subject: Re: [PATCH 7/7] OF/ACPI/I2C: Add generic match function for the
 aforementioned systems

On Wed, Jun 04, 2014 at 02:37:42PM +0200, Rafael J. Wysocki wrote:
> On Wednesday, June 04, 2014 01:09:56 PM Lee Jones wrote:
> > Currently this is a helper function for the I2C subsystem to aid the
> > matching of non-standard compatible strings and devices which use DT
> > and/or ACPI, but do not supply any nodes (see: [1] Method 4).  However,
> > it has been made more generic as it can be used to only make one call
> > for drivers which support any mixture of OF, ACPI and/or I2C matching.
> > 
> > The initial aim is for of_match_device() to be replaced by this call
> > in all I2C device drivers.
> > 
> > [1] Documentation/i2c/instantiating-devices
> > 
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> 
> Mika, can you please have a look at this, please?

I don't see any fundamental problems with this wrt. ACPI.

That said, I find it kind of weird to have generic function that then
has knowledge of how different buses do their matching.

I would rather see something like firmware_device_match(dev) that goes
and matches from DT/ACPI and leave bus specific match to happen internal
to that bus.

> 
> 
> > ---
> >  include/linux/match.h | 40 ++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 40 insertions(+)
> >  create mode 100644 include/linux/match.h
> > 
> > diff --git a/include/linux/match.h b/include/linux/match.h
> > new file mode 100644
> > index 0000000..20a08e2
> > --- /dev/null
> > +++ b/include/linux/match.h
> > @@ -0,0 +1,40 @@
> > +#include <linux/of.h>
> > +#include <linux/acpi.h>
> > +#include <linux/i2c.h>
> > +
> > +static void *device_match(struct device *dev)
> > +{
> > +	struct device_driver *driver = dev->driver;
> > +
> > +	if (!driver)
> > +		return NULL;
> > +
> > +	/* Attempt an OF style match */
> > +	if (IS_ENABLED(CONFIG_OF)) {
> > +		const struct of_device_id *of_match =
> > +			i2c_of_match_device(driver->of_match_table, dev);
> > +		if (of_match)
> > +			return (void *)of_match;
> > +	}
> > +
> > +	/* Then ACPI style match */
> > +	if (IS_ENABLED(CONFIG_ACPI)) {
> > +		const struct acpi_device_id *acpi_match	=
> > +			acpi_match_device(driver->acpi_match_table, dev);
> > +		if (acpi_match)
> > +			return (void *)acpi_match;
> > +	}
> > +
> > +	/* Finally an I2C match */
> > +	if (IS_ENABLED(CONFIG_I2C)) {
> > +		struct i2c_client *client = i2c_verify_client(dev);
> > +		struct i2c_driver *i2c_drv = to_i2c_driver(driver);
> > +		struct i2c_device_id *i2c_match;
> > +
> > +		i2c_match = i2c_match_id(i2c_drv->id_table, client);
> > +		if (i2c_match)
> > +			return (void *)i2c_match;
> > +	}
> > +
> > +	return NULL;
> > +}
> > 
> 
> -- 
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
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