linux-kernel - Re: [PATCH v3 1/2] power: supply: ltc2941-battery-gauge: Add OF device ID table

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Date:   Wed, 15 Mar 2017 22:10:22 +0100
From:   Sebastian Reichel <sre@...nel.org>
To:     Javier Martinez Canillas <javier@....samsung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v3 1/2] power: supply: ltc2941-battery-gauge: Add OF
 device ID table

Hi Javier,

On Wed, Mar 15, 2017 at 05:59:24PM -0300, Javier Martinez Canillas wrote:
> Hello Sebastian,
> 
> On 03/15/2017 05:55 PM, Sebastian Reichel wrote:
> > Hi,
> > 
> > On Wed, Mar 15, 2017 at 12:43:48AM -0300, Javier Martinez Canillas wrote:
> >> The driver doesn't have a struct of_device_id table but supported devices
> >> are registered via Device Trees. This is working on the assumption that a
> >> I2C device registered via OF will always match a legacy I2C device ID and
> >> that the MODALIAS reported will always be of the form i2c:<device>.
> > 
> > I don't get hits for "grep -r ltc294[13]" in arch/.
> >
> 
> There isn't a mainline DTS that use these but the compatible strings (without a
> vendor prefix) are listed in the following DT binding document:
> 
> Documentation/devicetree/bindings/power/supply/ltc2941.txt.

Looks like I didn't notice when I merged the binding document :(

> >> But this could change in the future so the correct approach is to have an
> >> OF device ID table if the devices are registered via OF.
> >>
> >> The compatible strings don't have a vendor prefix because that's how it's
> >> used currently, and changing this will be a Device Tree ABI break.
> > 
> > I think the DT strings should have a vendor prefix.
> > So I will only queue this with an explicit Acked-By from Rob or Mark.
> >
> 
> Yes, I agree with you. I don't know though what should happen with DT bindings
> that mentions a compatible without a vendor prefix as the one for this driver.

Adding Rob, Mark (DT binding maintainers) and Mike (submitter of
the DT binding). I think we should add vendor prefix. If it is
actually used we could keep the variant without the vendor prefix
with a deprecation notice in the DT binding document.

-- Sebastian

> > -- Sebastian
> > 
> >> Changes in v3:
> >> - Don't use of_match_ptr() to avoid build warning when CONFIG_OF is disabled.
> >>
> >> Changes in v2:
> >>  Fix build warning reported by kbuild test robot.
> >> - Fix wrong compatible strings due a copy & paste error.
> >>
> >>  drivers/power/supply/ltc2941-battery-gauge.c | 19 +++++++++++++++++--
> >>  1 file changed, 17 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/power/supply/ltc2941-battery-gauge.c b/drivers/power/supply/ltc2941-battery-gauge.c
> >> index 4adf2ba021ce..d3052be1bead 100644
> >> --- a/drivers/power/supply/ltc2941-battery-gauge.c
> >> +++ b/drivers/power/supply/ltc2941-battery-gauge.c
> >> @@ -9,6 +9,7 @@
> >>   */
> >>  #include <linux/kernel.h>
> >>  #include <linux/module.h>
> >> +#include <linux/of_device.h>
> >>  #include <linux/types.h>
> >>  #include <linux/errno.h>
> >>  #include <linux/swab.h>
> >> @@ -61,7 +62,7 @@ struct ltc294x_info {
> >>  	struct power_supply *supply;	/* Supply pointer */
> >>  	struct power_supply_desc supply_desc;	/* Supply description */
> >>  	struct delayed_work work;	/* Work scheduler */
> >> -	int num_regs;	/* Number of registers (chip type) */
> >> +	unsigned long num_regs;	/* Number of registers (chip type) */
> >>  	int charge;	/* Last charge register content */
> >>  	int r_sense;	/* mOhm */
> >>  	int Qlsb;	/* nAh */
> >> @@ -387,7 +388,7 @@ static int ltc294x_i2c_probe(struct i2c_client *client,
> >>  
> >>  	np = of_node_get(client->dev.of_node);
> >>  
> >> -	info->num_regs = id->driver_data;
> >> +	info->num_regs = (unsigned long)of_device_get_match_data(&client->dev);
> >>  	info->supply_desc.name = np->name;
> >>  
> >>  	/* r_sense can be negative, when sense+ is connected to the battery
> >> @@ -497,9 +498,23 @@ static const struct i2c_device_id ltc294x_i2c_id[] = {
> >>  };
> >>  MODULE_DEVICE_TABLE(i2c, ltc294x_i2c_id);
> >>  
> >> +static const struct of_device_id ltc294x_i2c_of_match[] = {
> >> +	{
> >> +		.compatible = "ltc2941",
> >> +		.data = (void *)LTC2941_NUM_REGS
> >> +	},
> >> +	{
> >> +		.compatible = "ltc2943",
> >> +		.data = (void *)LTC2943_NUM_REGS
> >> +	},
> >> +	{ },
> >> +};
> >> +MODULE_DEVICE_TABLE(of, ltc294x_i2c_of_match);
> >> +
> >>  static struct i2c_driver ltc294x_driver = {
> >>  	.driver = {
> >>  		.name	= "LTC2941",
> >> +		.of_match_table = ltc294x_i2c_of_match,
> >>  		.pm	= LTC294X_PM_OPS,
> >>  	},
> >>  	.probe		= ltc294x_i2c_probe,
> >> -- 
> >> 2.9.3
> >>
> 
> Best regards,
> -- 
> Javier Martinez Canillas
> Open Source Group
> Samsung Research America

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