Re: [PATCH 1/3] iio: ak8975 : Add AK8963 compatibility mode support

[Lars-Peter Clausen <lars@metafoo.de>]

On 03/11/2014 10:15 PM, Srinivas Pandruvada wrote:
> AK8963 and AK8975 use same register definitions, except the range
> of X,Y,Z values. Added support of 8963 based on i2c_device_id.
> Unfortunately there is no way to detect the type via registers,
> both device registers return 0x48 as id of chipset.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

Hi,

a few small comments.

> ---
>   drivers/iio/magnetometer/Kconfig  |  3 ++-
>   drivers/iio/magnetometer/ak8975.c | 40 +++++++++++++++++++++++++++++++++++----
>   2 files changed, 38 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
> index d86d226..05a364c54 100644
> --- a/drivers/iio/magnetometer/Kconfig
> +++ b/drivers/iio/magnetometer/Kconfig
> @@ -11,7 +11,8 @@ config AK8975
>   	depends on GPIOLIB
>   	help
>   	  Say yes here to build support for Asahi Kasei AK8975 3-Axis
> -	  Magnetometer.
> +	  Magnetometer. This driver can also support AK8963, if i2c
> +	  device name is identified as ak8963.
>
>   	  To compile this driver as a module, choose M here: the module
>   	  will be called ak8975.
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 0542354..a55c94f 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -85,7 +85,15 @@
>   #define AK8975_MAX_CONVERSION_TIMEOUT	500
>   #define AK8975_CONVERSION_DONE_POLL_TIME 10
>   #define AK8975_DATA_READY_TIMEOUT	((100*HZ)/1000)
> -#define RAW_TO_GAUSS(asa) ((((asa) + 128) * 3000) / 256)
> +#define RAW_TO_GAUSS_8975(asa) ((((asa) + 128) * 3000) / 256)
> +#define RAW_TO_GAUSS_8963(asa) ((((asa) + 128) * 6000) / 256)
> +
> +/* Compatible Asahi Kasei Compass parts */
> +enum asahi_compass_chipset {
> +	AK8975,
> +	AK8963,
> +	AK_INVALID,

Not sure if you need AK_INVALID, it is never used.

> +};
>
>   /*
>    * Per-instance context data for the device.
> @@ -101,6 +109,7 @@ struct ak8975_data {
>   	int			eoc_irq;
>   	wait_queue_head_t	data_ready_queue;
>   	unsigned long		flags;
> +	int			chipset;

enum asahi_compass_chipset ...

>   };
>
>   static const int ak8975_index_to_reg[] = {
> @@ -272,9 +281,21 @@ static int ak8975_setup(struct i2c_client *client)
>    * Since ASA doesn't change, we cache the resultant scale factor into the
>    * device context in ak8975_setup().
>    */
> -	data->raw_to_gauss[0] = RAW_TO_GAUSS(data->asa[0]);
> -	data->raw_to_gauss[1] = RAW_TO_GAUSS(data->asa[1]);
> -	data->raw_to_gauss[2] = RAW_TO_GAUSS(data->asa[2]);
> +	if (data->chipset == AK8963) {
> +		/*
> +		 * H range is +-8190 and magnetometer range is +-4912.
> +		 * So HuT using the above explanation for 8975,
> +		 * 4912/8190 = ~ 6/10.
> +		 * So the Hadj should use 6/10 instead of 3/10.
> +		 */
> +		data->raw_to_gauss[0] = RAW_TO_GAUSS_8963(data->asa[0]);
> +		data->raw_to_gauss[1] = RAW_TO_GAUSS_8963(data->asa[1]);
> +		data->raw_to_gauss[2] = RAW_TO_GAUSS_8963(data->asa[2]);
> +	} else {
> +		data->raw_to_gauss[0] = RAW_TO_GAUSS_8975(data->asa[0]);
> +		data->raw_to_gauss[1] = RAW_TO_GAUSS_8975(data->asa[1]);
> +		data->raw_to_gauss[2] = RAW_TO_GAUSS_8975(data->asa[2]);
> +	}
>
>   	return 0;
>   }
> @@ -499,6 +520,16 @@ static int ak8975_probe(struct i2c_client *client,
>   	data->eoc_gpio = eoc_gpio;
>   	data->eoc_irq = 0;
>
> +	if (id) {

id will never be NULL.

> +		data->chipset = (int)(id->driver_data);
> +		if (data->chipset == AK8963)
> +			dev_dbg(&client->dev,
> +				"AK8975 driver is running in AK8963 mode\n");
> +		else
> +			dev_dbg(&client->dev,
> +				"AK8975 driver is running in normal mode\n");

How about printing just id->name, this way you do not have to add a new else 
branch when a new part is supported.

> +	}
> +
>   	/* Perform some basic start-of-day setup of the device. */
>   	err = ak8975_setup(client);
>   	if (err < 0) {
> @@ -552,6 +583,7 @@ static int ak8975_remove(struct i2c_client *client)
>
>   static const struct i2c_device_id ak8975_id[] = {
>   	{"ak8975", 0},

Should change the 0 to AK8975

> +	{"ak8963", AK8963},
>   	{}
>   };
>
>