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

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Date:	Thu, 5 Jun 2014 11:37:09 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Grant Likely <grant.likely@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	wsa@...-dreams.de, 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 Thu, 05 Jun 2014, Grant Likely wrote:

> On Wed,  4 Jun 2014 13:09:56 +0100, Lee Jones <lee.jones@...aro.org> 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>
> 
> I don't like this. It drops all type safety on the match entry
> and the caller has no idea what it got back.

Okay, so what's the best way forward?

Introduce a i2c_of_match_device() call instead?

> > ---
> >  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;
> > +}
> 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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