linux-kernel - Re: [PATCH 8/8] iio: mma8452: add devicetree property to allow all pin wirings

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Message-ID: <20150727142336.GB10821@leverpostej>
Date:	Mon, 27 Jul 2015 15:23:36 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Martin Kepplinger <martink@...teo.de>
Cc:	"jic23@...nel.org" <jic23@...nel.org>,
	"knaack.h@....de" <knaack.h@....de>,
	"lars@...afoo.de" <lars@...afoo.de>,
	"pmeerw@...erw.net" <pmeerw@...erw.net>,
	"mfuzzey@...keon.com" <mfuzzey@...keon.com>,
	"roberta.dobrescu@...il.com" <roberta.dobrescu@...il.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"christoph.muellner@...obroma-systems.com" 
	<christoph.muellner@...obroma-systems.com>,
	Martin Kepplinger <martin.kepplinger@...obroma-systems.com>
Subject: Re: [PATCH 8/8] iio: mma8452: add devicetree property to allow all
 pin wirings

On Mon, Jul 27, 2015 at 03:08:15PM +0100, Martin Kepplinger wrote:
> For the devices supported by the mma8452 driver, two interrupt pins are
> available to route the interrupt signals to. By default INT1 is assumed.
> 
> This adds a bitmask DT property for users to configure interrupt sources
> for INT2, if that is the wired interrupt pin for them.

This sounds like configureation rather than a HW property. Why does this
need to be in the DT?

> This is important for everyone to be able to use this driver, no matter
> how their chip is wired. At the moment, only 0xff for using INT2 for all
> available interrupt sources is supported. See the devicetree documentation
> file for more details.
> 
> Since this doesn't change the default behaviour, it doesn't break anything
> for existing users.
> 
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...obroma-systems.com>
> Signed-off-by: Christoph Muellner <christoph.muellner@...obroma-systems.com>
> ---
>  .../devicetree/bindings/iio/accel/mma8452.txt        |  4 ++++
>  drivers/iio/accel/mma8452.c                          | 20 +++++++++++++-------
>  2 files changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/accel/mma8452.txt b/Documentation/devicetree/bindings/iio/accel/mma8452.txt
> index 8d98e05..738a430 100644
> --- a/Documentation/devicetree/bindings/iio/accel/mma8452.txt
> +++ b/Documentation/devicetree/bindings/iio/accel/mma8452.txt
> @@ -10,6 +10,9 @@ Optional properties:
>  
>    - interrupt-parent: should be the phandle for the interrupt controller
>    - interrupts: interrupt mapping for GPIO IRQ
> +  - use_int2: bitmask to choose interrupt sources assumed to be wired to
> +    interrupt pin INT2 instead of INT1. Only 0xff (INT2 for every interrupt
> +    source) is supported at the moment.

s/_/-/ in property names, please.

We generally avoid bitmasks in properties, and we also usually exepct a
full cell even if data is smaller. The fact that you expect /bits/ 8 
must be documented here if that's truly necessary.

Thanks,
Mark

>  
>  Example:
>  
> @@ -18,4 +21,5 @@ Example:
>  		reg = <0x1d>;
>  		interrupt-parent = <&gpio1>;
>  		interrupts = <5 0>;
> +		use_int2 = /bits/ 8 <0xff>;
>  	};
> diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
> index 918ab59..a03836b1 100644
> --- a/drivers/iio/accel/mma8452.c
> +++ b/drivers/iio/accel/mma8452.c
> @@ -1028,8 +1028,9 @@ static int mma8452_probe(struct i2c_client *client,
>  {
>  	struct mma8452_data *data;
>  	struct iio_dev *indio_dev;
> -	int ret;
>  	const struct of_device_id *match;
> +	int ret;
> +	u8 int2;
>  
>  	match = of_match_device(mma8452_dt_ids, &client->dev);
>  	if (!match) {
> @@ -1104,12 +1105,17 @@ static int mma8452_probe(struct i2c_client *client,
>  		int enabled_interrupts = MMA8452_INT_TRANS |
>  					 MMA8452_INT_FF_MT;
>  
> -		/* Assume wired to INT1 pin */
> -		ret = i2c_smbus_write_byte_data(client,
> -						MMA8452_CTRL_REG5,
> -						supported_interrupts);
> -		if (ret < 0)
> -			return ret;
> +		of_property_read_u8(client->dev.of_node, "use_int2", &int2);
> +		if (int2 == 0xff) {
> +			dev_dbg(&client->dev, "use interrupt line INT2\n");
> +		} else {
> +			dev_dbg(&client->dev, "use interrupt line INT1\n");
> +			ret = i2c_smbus_write_byte_data(client,
> +							MMA8452_CTRL_REG5,
> +							supported_interrupts);
> +			if (ret < 0)
> +				return ret;
> +		}
>  
>  		ret = i2c_smbus_write_byte_data(client,
>  						MMA8452_CTRL_REG4,
> -- 
> 2.1.4
> 
--
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