[PATCH 0/3] Enable AK8963 conneted via INV6500

[PATCH 0/3] Enable AK8963 conneted via INV6500

[Srinivas Pandruvada]

Now we have i2c-mux for invensense mpu6050/mpu6500 is merged, this patchset
enables sensors routed through this.
In this series enabling AK8975/AK8963. This device is connected to main
cpu i2c bus via invensense bypass mode enabled by i2c-mux.

Srinivas Pandruvada (3):
  iio: imu: inv_mpu6050: ACPI enumeration
  iio: imu: inv_mpu6050: Added adapter class
  iio: ak8975: Added autodetect feature for ACPI

 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 11 +++++++++-
 drivers/iio/magnetometer/ak8975.c          | 35 ++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

-- 
1.9.3

[PATCH 1/3] iio: imu: inv_mpu6050: ACPI enumeration

[Srinivas Pandruvada]

Added changes so that the module can be enumerated via ACPI.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
index 6d2c115..f73e60b 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
@@ -24,6 +24,7 @@
 #include <linux/spinlock.h>
 #include <linux/iio/iio.h>
 #include <linux/i2c-mux.h>
+#include <linux/acpi.h>
 #include "inv_mpu_iio.h"
 
 /*
@@ -875,6 +876,13 @@ static const struct i2c_device_id inv_mpu_id[] = {
 
 MODULE_DEVICE_TABLE(i2c, inv_mpu_id);
 
+static const struct acpi_device_id inv_acpi_match[] = {
+	{"INVN6500", 0},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(acpi, inv_acpi_match);
+
 static struct i2c_driver inv_mpu_driver = {
 	.probe		=	inv_mpu_probe,
 	.remove		=	inv_mpu_remove,
@@ -883,6 +891,7 @@ static struct i2c_driver inv_mpu_driver = {
 		.owner	=	THIS_MODULE,
 		.name	=	"inv-mpu6050",
 		.pm     =       INV_MPU6050_PMOPS,
+		.acpi_match_table = ACPI_PTR(inv_acpi_match),
 	},
 };
 
-- 
1.9.3

[PATCH 2/3] iio: imu: inv_mpu6050: Added adapter class

[Srinivas Pandruvada]

To use i2c auto detect to work we need to have a non zero class.
The closest class is I2C_CLASS_HWMON, as it defined to be used
with all hw monitoring drivers.

Also this class is already used by some iio driver, hid drivers, led
and misc drivers. So this is not new that this is used outside
hwmon drivers.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
index f73e60b..4af2d24 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
@@ -813,7 +813,7 @@ static int inv_mpu_probe(struct i2c_client *client,
 	st->mux_adapter = i2c_add_mux_adapter(client->adapter,
 					      &client->dev,
 					      indio_dev,
-					      0, 0, 0,
+					      0, 0, I2C_CLASS_HWMON,
 					      inv_mpu6050_select_bypass,
 					      inv_mpu6050_deselect_bypass);
 	if (!st->mux_adapter) {
-- 
1.9.3

[PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

Using i2c auto detect feature and auto device creation feature,
enumerate ak8975 device, by checking their presence.
This is needed because when this device sits behind an i2c mux, there
is no way to define i2c mux in ACPI. This will enable ak8975 on
windows based tablets/laptops running Linux when connected via a mux.
Since DT model already can define an i2c mux and devices connected to
it, this feature is only enabled for ACPI.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/iio/magnetometer/ak8975.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
index 0d10a4b..c3455bd 100644
--- a/drivers/iio/magnetometer/ak8975.c
+++ b/drivers/iio/magnetometer/ak8975.c
@@ -820,6 +820,36 @@ static const struct i2c_device_id ak8975_id[] = {
 
 MODULE_DEVICE_TABLE(i2c, ak8975_id);
 
+#if defined(CONFIG_ACPI)
+static int ak8975_detect(struct i2c_client *temp_client,
+			 struct i2c_board_info *info)
+{
+	struct i2c_adapter *adapter;
+	int i, j;
+	int ret;
+
+	/* autodetect only when we are behind a mux */
+	adapter = i2c_parent_is_i2c_adapter(temp_client->adapter);
+	if (!adapter)
+		return -ENODEV;
+
+	for (i = 0; i < AK_MAX_TYPE; ++i) {
+		ret = ak8975_who_i_am(temp_client, i);
+		if (ret >= 0) {
+			for (j = 0; j < ARRAY_SIZE(ak8975_id) - 1; ++j) {
+				if (i == (int)ak8975_id[j].driver_data) {
+					strlcpy(info->type, ak8975_id[j].name,
+						I2C_NAME_SIZE);
+					return 0;
+				}
+			}
+		}
+	}
+
+	return -ENODEV;
+}
+#endif
+
 static const struct of_device_id ak8975_of_match[] = {
 	{ .compatible = "asahi-kasei,ak8975", },
 	{ .compatible = "ak8975", },
@@ -841,6 +871,11 @@ static struct i2c_driver ak8975_driver = {
 	},
 	.probe		= ak8975_probe,
 	.id_table	= ak8975_id,
+#if defined(CONFIG_ACPI)
+	.class		= I2C_CLASS_HWMON,
+	.address_list	= I2C_ADDRS(0x0C, 0x0D, 0x0E, 0x0F),
+	.detect		= ak8975_detect,
+#endif
 };
 module_i2c_driver(ak8975_driver);
 
-- 
1.9.3

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Lars-Peter Clausen]

Added I2C to Cc.

On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> Using i2c auto detect feature and auto device creation feature,
> enumerate ak8975 device, by checking their presence.
> This is needed because when this device sits behind an i2c mux, there
> is no way to define i2c mux in ACPI. This will enable ak8975 on
> windows based tablets/laptops running Linux when connected via a mux.
> Since DT model already can define an i2c mux and devices connected to
> it, this feature is only enabled for ACPI.
>

This is quite a bit of a hack. Did they decide to not include the device in 
the ACPI description at all or is there a special id for INV6050+AK8975?

How does Windows decide whether there is a device or not?

> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> ---
>   drivers/iio/magnetometer/ak8975.c | 35 +++++++++++++++++++++++++++++++++++
>   1 file changed, 35 insertions(+)
>
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 0d10a4b..c3455bd 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -820,6 +820,36 @@ static const struct i2c_device_id ak8975_id[] = {
>
>   MODULE_DEVICE_TABLE(i2c, ak8975_id);
>
> +#if defined(CONFIG_ACPI)
> +static int ak8975_detect(struct i2c_client *temp_client,
> +			 struct i2c_board_info *info)
> +{
> +	struct i2c_adapter *adapter;
> +	int i, j;
> +	int ret;
> +
> +	/* autodetect only when we are behind a mux */
> +	adapter = i2c_parent_is_i2c_adapter(temp_client->adapter);
> +	if (!adapter)
> +		return -ENODEV;
> +
> +	for (i = 0; i < AK_MAX_TYPE; ++i) {
> +		ret = ak8975_who_i_am(temp_client, i);
> +		if (ret >= 0) {
> +			for (j = 0; j < ARRAY_SIZE(ak8975_id) - 1; ++j) {
> +				if (i == (int)ak8975_id[j].driver_data) {
> +					strlcpy(info->type, ak8975_id[j].name,
> +						I2C_NAME_SIZE);
> +					return 0;
> +				}
> +			}
> +		}
> +	}
> +
> +	return -ENODEV;
> +}
> +#endif
> +
>   static const struct of_device_id ak8975_of_match[] = {
>   	{ .compatible = "asahi-kasei,ak8975", },
>   	{ .compatible = "ak8975", },
> @@ -841,6 +871,11 @@ static struct i2c_driver ak8975_driver = {
>   	},
>   	.probe		= ak8975_probe,
>   	.id_table	= ak8975_id,
> +#if defined(CONFIG_ACPI)
> +	.class		= I2C_CLASS_HWMON,
> +	.address_list	= I2C_ADDRS(0x0C, 0x0D, 0x0E, 0x0F),
> +	.detect		= ak8975_detect,

In contrast to the commit message this is always enabled if the kernel 
contains ACPI support, not if the device is a ACPI device.

> +#endif
>   };
>   module_i2c_driver(ak8975_driver);
>
>

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Lars-Peter Clausen]

Added I2C to Cc.

On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> Using i2c auto detect feature and auto device creation feature,
> enumerate ak8975 device, by checking their presence.
> This is needed because when this device sits behind an i2c mux, there
> is no way to define i2c mux in ACPI. This will enable ak8975 on
> windows based tablets/laptops running Linux when connected via a mux.
> Since DT model already can define an i2c mux and devices connected to
> it, this feature is only enabled for ACPI.
>

This is quite a bit of a hack. Did they decide to not include the device in 
the ACPI description at all or is there a special id for INV6050+AK8975?

How does Windows decide whether there is a device or not?

> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> ---
>   drivers/iio/magnetometer/ak8975.c | 35 +++++++++++++++++++++++++++++++++++
>   1 file changed, 35 insertions(+)
>
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 0d10a4b..c3455bd 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -820,6 +820,36 @@ static const struct i2c_device_id ak8975_id[] = {
>
>   MODULE_DEVICE_TABLE(i2c, ak8975_id);
>
> +#if defined(CONFIG_ACPI)
> +static int ak8975_detect(struct i2c_client *temp_client,
> +			 struct i2c_board_info *info)
> +{
> +	struct i2c_adapter *adapter;
> +	int i, j;
> +	int ret;
> +
> +	/* autodetect only when we are behind a mux */
> +	adapter = i2c_parent_is_i2c_adapter(temp_client->adapter);
> +	if (!adapter)
> +		return -ENODEV;
> +
> +	for (i = 0; i < AK_MAX_TYPE; ++i) {
> +		ret = ak8975_who_i_am(temp_client, i);
> +		if (ret >= 0) {
> +			for (j = 0; j < ARRAY_SIZE(ak8975_id) - 1; ++j) {
> +				if (i == (int)ak8975_id[j].driver_data) {
> +					strlcpy(info->type, ak8975_id[j].name,
> +						I2C_NAME_SIZE);
> +					return 0;
> +				}
> +			}
> +		}
> +	}
> +
> +	return -ENODEV;
> +}
> +#endif
> +
>   static const struct of_device_id ak8975_of_match[] = {
>   	{ .compatible = "asahi-kasei,ak8975", },
>   	{ .compatible = "ak8975", },
> @@ -841,6 +871,11 @@ static struct i2c_driver ak8975_driver = {
>   	},
>   	.probe		= ak8975_probe,
>   	.id_table	= ak8975_id,
> +#if defined(CONFIG_ACPI)
> +	.class		= I2C_CLASS_HWMON,
> +	.address_list	= I2C_ADDRS(0x0C, 0x0D, 0x0E, 0x0F),
> +	.detect		= ak8975_detect,

In contrast to the commit message this is always enabled if the kernel 
contains ACPI support, not if the device is a ACPI device.

> +#endif
>   };
>   module_i2c_driver(ak8975_driver);
>
>

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote: 
> Added I2C to Cc.
> 
> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> > Using i2c auto detect feature and auto device creation feature,
> > enumerate ak8975 device, by checking their presence.
> > This is needed because when this device sits behind an i2c mux, there
> > is no way to define i2c mux in ACPI. This will enable ak8975 on
> > windows based tablets/laptops running Linux when connected via a mux.
> > Since DT model already can define an i2c mux and devices connected to
> > it, this feature is only enabled for ACPI.
> >
> 
> This is quite a bit of a hack.
Why?
Auto detect is standard feature of i2c devices. This is using standard
auto detect feature provided by the framework. 
>  Did they decide to not include the device in 
> the ACPI description at all or is there a special id for INV6050+AK8975?
This device needs has one combined id. Windows has a singe driver
processing both as a combo device. 
> 
> How does Windows decide whether there is a device or not?
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> > ---
> >   drivers/iio/magnetometer/ak8975.c | 35 +++++++++++++++++++++++++++++++++++
> >   1 file changed, 35 insertions(+)
> >
> > diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> > index 0d10a4b..c3455bd 100644
> > --- a/drivers/iio/magnetometer/ak8975.c
> > +++ b/drivers/iio/magnetometer/ak8975.c
> > @@ -820,6 +820,36 @@ static const struct i2c_device_id ak8975_id[] = {
> >
> >   MODULE_DEVICE_TABLE(i2c, ak8975_id);
> >
> > +#if defined(CONFIG_ACPI)
> > +static int ak8975_detect(struct i2c_client *temp_client,
> > +			 struct i2c_board_info *info)
> > +{
> > +	struct i2c_adapter *adapter;
> > +	int i, j;
> > +	int ret;
> > +
> > +	/* autodetect only when we are behind a mux */
> > +	adapter = i2c_parent_is_i2c_adapter(temp_client->adapter);
> > +	if (!adapter)
> > +		return -ENODEV;
> > +
> > +	for (i = 0; i < AK_MAX_TYPE; ++i) {
> > +		ret = ak8975_who_i_am(temp_client, i);
> > +		if (ret >= 0) {
> > +			for (j = 0; j < ARRAY_SIZE(ak8975_id) - 1; ++j) {
> > +				if (i == (int)ak8975_id[j].driver_data) {
> > +					strlcpy(info->type, ak8975_id[j].name,
> > +						I2C_NAME_SIZE);
> > +					return 0;
> > +				}
> > +			}
> > +		}
> > +	}
> > +
> > +	return -ENODEV;
> > +}
> > +#endif
> > +
> >   static const struct of_device_id ak8975_of_match[] = {
> >   	{ .compatible = "asahi-kasei,ak8975", },
> >   	{ .compatible = "ak8975", },
> > @@ -841,6 +871,11 @@ static struct i2c_driver ak8975_driver = {
> >   	},
> >   	.probe		= ak8975_probe,
> >   	.id_table	= ak8975_id,
> > +#if defined(CONFIG_ACPI)
> > +	.class		= I2C_CLASS_HWMON,
> > +	.address_list	= I2C_ADDRS(0x0C, 0x0D, 0x0E, 0x0F),
> > +	.detect		= ak8975_detect,
> 
> In contrast to the commit message this is always enabled if the kernel 
> contains ACPI support, not if the device is a ACPI device.
Yes. You don't enable ACPI if you don't need it. It will bring in lots
of builtin code if someone did that. 
> 
> > +#endif
> >   };
> >   module_i2c_driver(ak8975_driver);
> >
> >
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote: 
> Added I2C to Cc.
> 
> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> > Using i2c auto detect feature and auto device creation feature,
> > enumerate ak8975 device, by checking their presence.
> > This is needed because when this device sits behind an i2c mux, there
> > is no way to define i2c mux in ACPI. This will enable ak8975 on
> > windows based tablets/laptops running Linux when connected via a mux.
> > Since DT model already can define an i2c mux and devices connected to
> > it, this feature is only enabled for ACPI.
> >
> 
> This is quite a bit of a hack.
Why?
Auto detect is standard feature of i2c devices. This is using standard
auto detect feature provided by the framework. 
>  Did they decide to not include the device in 
> the ACPI description at all or is there a special id for INV6050+AK8975?
This device needs has one combined id. Windows has a singe driver
processing both as a combo device. 
> 
> How does Windows decide whether there is a device or not?
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> > ---
> >   drivers/iio/magnetometer/ak8975.c | 35 +++++++++++++++++++++++++++++++++++
> >   1 file changed, 35 insertions(+)
> >
> > diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> > index 0d10a4b..c3455bd 100644
> > --- a/drivers/iio/magnetometer/ak8975.c
> > +++ b/drivers/iio/magnetometer/ak8975.c
> > @@ -820,6 +820,36 @@ static const struct i2c_device_id ak8975_id[] = {
> >
> >   MODULE_DEVICE_TABLE(i2c, ak8975_id);
> >
> > +#if defined(CONFIG_ACPI)
> > +static int ak8975_detect(struct i2c_client *temp_client,
> > +			 struct i2c_board_info *info)
> > +{
> > +	struct i2c_adapter *adapter;
> > +	int i, j;
> > +	int ret;
> > +
> > +	/* autodetect only when we are behind a mux */
> > +	adapter = i2c_parent_is_i2c_adapter(temp_client->adapter);
> > +	if (!adapter)
> > +		return -ENODEV;
> > +
> > +	for (i = 0; i < AK_MAX_TYPE; ++i) {
> > +		ret = ak8975_who_i_am(temp_client, i);
> > +		if (ret >= 0) {
> > +			for (j = 0; j < ARRAY_SIZE(ak8975_id) - 1; ++j) {
> > +				if (i == (int)ak8975_id[j].driver_data) {
> > +					strlcpy(info->type, ak8975_id[j].name,
> > +						I2C_NAME_SIZE);
> > +					return 0;
> > +				}
> > +			}
> > +		}
> > +	}
> > +
> > +	return -ENODEV;
> > +}
> > +#endif
> > +
> >   static const struct of_device_id ak8975_of_match[] = {
> >   	{ .compatible = "asahi-kasei,ak8975", },
> >   	{ .compatible = "ak8975", },
> > @@ -841,6 +871,11 @@ static struct i2c_driver ak8975_driver = {
> >   	},
> >   	.probe		= ak8975_probe,
> >   	.id_table	= ak8975_id,
> > +#if defined(CONFIG_ACPI)
> > +	.class		= I2C_CLASS_HWMON,
> > +	.address_list	= I2C_ADDRS(0x0C, 0x0D, 0x0E, 0x0F),
> > +	.detect		= ak8975_detect,
> 
> In contrast to the commit message this is always enabled if the kernel 
> contains ACPI support, not if the device is a ACPI device.
Yes. You don't enable ACPI if you don't need it. It will bring in lots
of builtin code if someone did that. 
> 
> > +#endif
> >   };
> >   module_i2c_driver(ak8975_driver);
> >
> >
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Lars-Peter Clausen]

On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
>> Added I2C to Cc.
>>
>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
>>> Using i2c auto detect feature and auto device creation feature,
>>> enumerate ak8975 device, by checking their presence.
>>> This is needed because when this device sits behind an i2c mux, there
>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
>>> windows based tablets/laptops running Linux when connected via a mux.
>>> Since DT model already can define an i2c mux and devices connected to
>>> it, this feature is only enabled for ACPI.
>>>
>>
>> This is quite a bit of a hack.
> Why?
> Auto detect is standard feature of i2c devices. This is using standard
> auto detect feature provided by the framework.

Auto detect is ugly, slow and unreliable, it's kind of like the last straw 
if nothing else works.

Autodetect will be executed for every adapter with every device that 
supports auto detection, so you want to keep the amount of devices that do 
auto detection to a minimum in order to avoid both false positives and 
reduce boot time.


>>   Did they decide to not include the device in
>> the ACPI description at all or is there a special id for INV6050+AK8975?
> This device needs has one combined id. Windows has a singe driver
> processing both as a combo device.

Ok, then use the combined id to instantiate INV6050+AK8975.

- Lars

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Lars-Peter Clausen]

On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
>> Added I2C to Cc.
>>
>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
>>> Using i2c auto detect feature and auto device creation feature,
>>> enumerate ak8975 device, by checking their presence.
>>> This is needed because when this device sits behind an i2c mux, there
>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
>>> windows based tablets/laptops running Linux when connected via a mux.
>>> Since DT model already can define an i2c mux and devices connected to
>>> it, this feature is only enabled for ACPI.
>>>
>>
>> This is quite a bit of a hack.
> Why?
> Auto detect is standard feature of i2c devices. This is using standard
> auto detect feature provided by the framework.

Auto detect is ugly, slow and unreliable, it's kind of like the last straw 
if nothing else works.

Autodetect will be executed for every adapter with every device that 
supports auto detection, so you want to keep the amount of devices that do 
auto detection to a minimum in order to avoid both false positives and 
reduce boot time.


>>   Did they decide to not include the device in
>> the ACPI description at all or is there a special id for INV6050+AK8975?
> This device needs has one combined id. Windows has a singe driver
> processing both as a combo device.

Ok, then use the combined id to instantiate INV6050+AK8975.

- Lars

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote: 
> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
> > On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
> >> Added I2C to Cc.
> >>
> >> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> >>> Using i2c auto detect feature and auto device creation feature,
> >>> enumerate ak8975 device, by checking their presence.
> >>> This is needed because when this device sits behind an i2c mux, there
> >>> is no way to define i2c mux in ACPI. This will enable ak8975 on
> >>> windows based tablets/laptops running Linux when connected via a mux.
> >>> Since DT model already can define an i2c mux and devices connected to
> >>> it, this feature is only enabled for ACPI.
> >>>
> >>
> >> This is quite a bit of a hack.
> > Why?
> > Auto detect is standard feature of i2c devices. This is using standard
> > auto detect feature provided by the framework.
> 
> Auto detect is ugly, slow and unreliable, it's kind of like the last straw 
> if nothing else works.
That is true here. You can't enumerate this device by ACPI. As discussed
before we created i2c mux in inv6050 so that we can use AK8975 in bypass
mode. I added some API to create i2c device on this mux, which Wolfram
didn't like. He wanted to enumerate using existing mechanisms. 
> 
> Autodetect will be executed for every adapter with every device that 
> supports auto detection, so you want to keep the amount of devices that do 
> auto detection to a minimum in order to avoid both false positives and 
> reduce boot time.
> 
> 
> >>   Did they decide to not include the device in
> >> the ACPI description at all or is there a special id for INV6050+AK8975?
> > This device needs has one combined id. Windows has a singe driver
> > processing both as a combo device.
> 
> Ok, then use the combined id to instantiate INV6050+AK8975.
No. The i2c address address is already consumed by INV6050 driver (which
is valid for INV6050 not AK8975).

> 
> - Lars
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote: 
> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
> > On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
> >> Added I2C to Cc.
> >>
> >> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> >>> Using i2c auto detect feature and auto device creation feature,
> >>> enumerate ak8975 device, by checking their presence.
> >>> This is needed because when this device sits behind an i2c mux, there
> >>> is no way to define i2c mux in ACPI. This will enable ak8975 on
> >>> windows based tablets/laptops running Linux when connected via a mux.
> >>> Since DT model already can define an i2c mux and devices connected to
> >>> it, this feature is only enabled for ACPI.
> >>>
> >>
> >> This is quite a bit of a hack.
> > Why?
> > Auto detect is standard feature of i2c devices. This is using standard
> > auto detect feature provided by the framework.
> 
> Auto detect is ugly, slow and unreliable, it's kind of like the last straw 
> if nothing else works.
That is true here. You can't enumerate this device by ACPI. As discussed
before we created i2c mux in inv6050 so that we can use AK8975 in bypass
mode. I added some API to create i2c device on this mux, which Wolfram
didn't like. He wanted to enumerate using existing mechanisms. 
> 
> Autodetect will be executed for every adapter with every device that 
> supports auto detection, so you want to keep the amount of devices that do 
> auto detection to a minimum in order to avoid both false positives and 
> reduce boot time.
> 
> 
> >>   Did they decide to not include the device in
> >> the ACPI description at all or is there a special id for INV6050+AK8975?
> > This device needs has one combined id. Windows has a singe driver
> > processing both as a combo device.
> 
> Ok, then use the combined id to instantiate INV6050+AK8975.
No. The i2c address address is already consumed by INV6050 driver (which
is valid for INV6050 not AK8975).

> 
> - Lars
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Lars-Peter Clausen]

On 12/18/2014 06:30 PM, Srinivas Pandruvada wrote:
> On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote:
>> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
>>> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
>>>> Added I2C to Cc.
>>>>
>>>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
>>>>> Using i2c auto detect feature and auto device creation feature,
>>>>> enumerate ak8975 device, by checking their presence.
>>>>> This is needed because when this device sits behind an i2c mux, there
>>>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
>>>>> windows based tablets/laptops running Linux when connected via a mux.
>>>>> Since DT model already can define an i2c mux and devices connected to
>>>>> it, this feature is only enabled for ACPI.
>>>>>
>>>>
>>>> This is quite a bit of a hack.
>>> Why?
>>> Auto detect is standard feature of i2c devices. This is using standard
>>> auto detect feature provided by the framework.
>>
>> Auto detect is ugly, slow and unreliable, it's kind of like the last straw
>> if nothing else works.
> That is true here. You can't enumerate this device by ACPI. As discussed
> before we created i2c mux in inv6050 so that we can use AK8975 in bypass
> mode. I added some API to create i2c device on this mux, which Wolfram
> didn't like. He wanted to enumerate using existing mechanisms.

If there is only a single ACPI ID that says this is a INV6050 with a AK8975 
attached then the way to handle this is to have a driver that binds to that id 
and creates both devices.

- Lars

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Lars-Peter Clausen]

On 12/18/2014 06:30 PM, Srinivas Pandruvada wrote:
> On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote:
>> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
>>> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
>>>> Added I2C to Cc.
>>>>
>>>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
>>>>> Using i2c auto detect feature and auto device creation feature,
>>>>> enumerate ak8975 device, by checking their presence.
>>>>> This is needed because when this device sits behind an i2c mux, there
>>>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
>>>>> windows based tablets/laptops running Linux when connected via a mux.
>>>>> Since DT model already can define an i2c mux and devices connected to
>>>>> it, this feature is only enabled for ACPI.
>>>>>
>>>>
>>>> This is quite a bit of a hack.
>>> Why?
>>> Auto detect is standard feature of i2c devices. This is using standard
>>> auto detect feature provided by the framework.
>>
>> Auto detect is ugly, slow and unreliable, it's kind of like the last straw
>> if nothing else works.
> That is true here. You can't enumerate this device by ACPI. As discussed
> before we created i2c mux in inv6050 so that we can use AK8975 in bypass
> mode. I added some API to create i2c device on this mux, which Wolfram
> didn't like. He wanted to enumerate using existing mechanisms.

If there is only a single ACPI ID that says this is a INV6050 with a AK8975 
attached then the way to handle this is to have a driver that binds to that id 
and creates both devices.

- Lars

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2014-12-18 at 18:54 +0100, Lars-Peter Clausen wrote: 
> On 12/18/2014 06:30 PM, Srinivas Pandruvada wrote:
> > On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote:
> >> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
> >>> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
> >>>> Added I2C to Cc.
> >>>>
> >>>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> >>>>> Using i2c auto detect feature and auto device creation feature,
> >>>>> enumerate ak8975 device, by checking their presence.
> >>>>> This is needed because when this device sits behind an i2c mux, there
> >>>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
> >>>>> windows based tablets/laptops running Linux when connected via a mux.
> >>>>> Since DT model already can define an i2c mux and devices connected to
> >>>>> it, this feature is only enabled for ACPI.
> >>>>>
> >>>>
> >>>> This is quite a bit of a hack.
> >>> Why?
> >>> Auto detect is standard feature of i2c devices. This is using standard
> >>> auto detect feature provided by the framework.
> >>
> >> Auto detect is ugly, slow and unreliable, it's kind of like the last straw
> >> if nothing else works.
> > That is true here. You can't enumerate this device by ACPI. As discussed
> > before we created i2c mux in inv6050 so that we can use AK8975 in bypass
> > mode. I added some API to create i2c device on this mux, which Wolfram
> > didn't like. He wanted to enumerate using existing mechanisms.
> 
> If there is only a single ACPI ID that says this is a INV6050 with a AK8975 
> attached then the way to handle this is to have a driver that binds to that id 
> and creates both devices.
Which address you will create device also adapter here is i2c mux
created by inv6050? You don't know i2c address of AK8975. To know AK8975
i2c address, even ugly hack to parse propriety vendor ACPI data, which
will change between to manufacturer.

> 
> - Lars
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2014-12-18 at 18:54 +0100, Lars-Peter Clausen wrote: 
> On 12/18/2014 06:30 PM, Srinivas Pandruvada wrote:
> > On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote:
> >> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
> >>> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
> >>>> Added I2C to Cc.
> >>>>
> >>>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
> >>>>> Using i2c auto detect feature and auto device creation feature,
> >>>>> enumerate ak8975 device, by checking their presence.
> >>>>> This is needed because when this device sits behind an i2c mux, there
> >>>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
> >>>>> windows based tablets/laptops running Linux when connected via a mux.
> >>>>> Since DT model already can define an i2c mux and devices connected to
> >>>>> it, this feature is only enabled for ACPI.
> >>>>>
> >>>>
> >>>> This is quite a bit of a hack.
> >>> Why?
> >>> Auto detect is standard feature of i2c devices. This is using standard
> >>> auto detect feature provided by the framework.
> >>
> >> Auto detect is ugly, slow and unreliable, it's kind of like the last straw
> >> if nothing else works.
> > That is true here. You can't enumerate this device by ACPI. As discussed
> > before we created i2c mux in inv6050 so that we can use AK8975 in bypass
> > mode. I added some API to create i2c device on this mux, which Wolfram
> > didn't like. He wanted to enumerate using existing mechanisms.
> 
> If there is only a single ACPI ID that says this is a INV6050 with a AK8975 
> attached then the way to handle this is to have a driver that binds to that id 
> and creates both devices.
Which address you will create device also adapter here is i2c mux
created by inv6050? You don't know i2c address of AK8975. To know AK8975
i2c address, even ugly hack to parse propriety vendor ACPI data, which
will change between to manufacturer.

> 
> - Lars
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Jonathan Cameron]

On 18/12/14 18:00, Srinivas Pandruvada wrote:
> On Thu, 2014-12-18 at 18:54 +0100, Lars-Peter Clausen wrote: 
>> On 12/18/2014 06:30 PM, Srinivas Pandruvada wrote:
>>> On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote:
>>>> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
>>>>> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
>>>>>> Added I2C to Cc.
>>>>>>
>>>>>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
>>>>>>> Using i2c auto detect feature and auto device creation feature,
>>>>>>> enumerate ak8975 device, by checking their presence.
>>>>>>> This is needed because when this device sits behind an i2c mux, there
>>>>>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
>>>>>>> windows based tablets/laptops running Linux when connected via a mux.
>>>>>>> Since DT model already can define an i2c mux and devices connected to
>>>>>>> it, this feature is only enabled for ACPI.
>>>>>>>
>>>>>>
>>>>>> This is quite a bit of a hack.
>>>>> Why?
>>>>> Auto detect is standard feature of i2c devices. This is using standard
>>>>> auto detect feature provided by the framework.
>>>>
>>>> Auto detect is ugly, slow and unreliable, it's kind of like the last straw
>>>> if nothing else works.
>>> That is true here. You can't enumerate this device by ACPI. As discussed
>>> before we created i2c mux in inv6050 so that we can use AK8975 in bypass
>>> mode. I added some API to create i2c device on this mux, which Wolfram
>>> didn't like. He wanted to enumerate using existing mechanisms.
>>
>> If there is only a single ACPI ID that says this is a INV6050 with a AK8975 
>> attached then the way to handle this is to have a driver that binds to that id 
>> and creates both devices.
> Which address you will create device also adapter here is i2c mux
> created by inv6050? You don't know i2c address of AK8975. To know AK8975
> i2c address, even ugly hack to parse propriety vendor ACPI data, which
> will change between to manufacturer.
> 
This is odd enough, that I'd like a wider range of views on it.

Wolfram - was this the approach you had in mind?
>>
>> - Lars
>>
> 
> 

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Jonathan Cameron]

On 18/12/14 18:00, Srinivas Pandruvada wrote:
> On Thu, 2014-12-18 at 18:54 +0100, Lars-Peter Clausen wrote: 
>> On 12/18/2014 06:30 PM, Srinivas Pandruvada wrote:
>>> On Thu, 2014-12-18 at 18:05 +0100, Lars-Peter Clausen wrote:
>>>> On 12/18/2014 05:52 PM, Srinivas Pandruvada wrote:
>>>>> On Thu, 2014-12-18 at 17:28 +0100, Lars-Peter Clausen wrote:
>>>>>> Added I2C to Cc.
>>>>>>
>>>>>> On 12/15/2014 10:19 PM, Srinivas Pandruvada wrote:
>>>>>>> Using i2c auto detect feature and auto device creation feature,
>>>>>>> enumerate ak8975 device, by checking their presence.
>>>>>>> This is needed because when this device sits behind an i2c mux, there
>>>>>>> is no way to define i2c mux in ACPI. This will enable ak8975 on
>>>>>>> windows based tablets/laptops running Linux when connected via a mux.
>>>>>>> Since DT model already can define an i2c mux and devices connected to
>>>>>>> it, this feature is only enabled for ACPI.
>>>>>>>
>>>>>>
>>>>>> This is quite a bit of a hack.
>>>>> Why?
>>>>> Auto detect is standard feature of i2c devices. This is using standard
>>>>> auto detect feature provided by the framework.
>>>>
>>>> Auto detect is ugly, slow and unreliable, it's kind of like the last straw
>>>> if nothing else works.
>>> That is true here. You can't enumerate this device by ACPI. As discussed
>>> before we created i2c mux in inv6050 so that we can use AK8975 in bypass
>>> mode. I added some API to create i2c device on this mux, which Wolfram
>>> didn't like. He wanted to enumerate using existing mechanisms.
>>
>> If there is only a single ACPI ID that says this is a INV6050 with a AK8975 
>> attached then the way to handle this is to have a driver that binds to that id 
>> and creates both devices.
> Which address you will create device also adapter here is i2c mux
> created by inv6050? You don't know i2c address of AK8975. To know AK8975
> i2c address, even ugly hack to parse propriety vendor ACPI data, which
> will change between to manufacturer.
> 
This is odd enough, that I'd like a wider range of views on it.

Wolfram - was this the approach you had in mind?
>>
>> - Lars
>>
> 
> 

Re: [PATCH 2/3] iio: imu: inv_mpu6050: Added adapter class

[Jonathan Cameron]

On 15/12/14 21:19, Srinivas Pandruvada wrote:
> To use i2c auto detect to work we need to have a non zero class.
> The closest class is I2C_CLASS_HWMON, as it defined to be used
> with all hw monitoring drivers.
> 
> Also this class is already used by some iio driver, hid drivers, led
> and misc drivers. So this is not new that this is used outside
> hwmon drivers.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Been meaning to sort this out for a while.  We really shouldn't be camping
on the HWMON class (nor should anyone else).

Wolfram, do you mind new classes being added?
> ---
>  drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> index f73e60b..4af2d24 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> @@ -813,7 +813,7 @@ static int inv_mpu_probe(struct i2c_client *client,
>  	st->mux_adapter = i2c_add_mux_adapter(client->adapter,
>  					      &client->dev,
>  					      indio_dev,
> -					      0, 0, 0,
> +					      0, 0, I2C_CLASS_HWMON,
>  					      inv_mpu6050_select_bypass,
>  					      inv_mpu6050_deselect_bypass);
>  	if (!st->mux_adapter) {
> 

Re: [PATCH 1/3] iio: imu: inv_mpu6050: ACPI enumeration

[Jonathan Cameron]

On 15/12/14 21:19, Srinivas Pandruvada wrote:
> Added changes so that the module can be enumerated via ACPI.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
As this one stands on it's own.

Applied to the togreg branch of iio.git.

Thanks

Jonathan
> ---
>  drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> index 6d2c115..f73e60b 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> @@ -24,6 +24,7 @@
>  #include <linux/spinlock.h>
>  #include <linux/iio/iio.h>
>  #include <linux/i2c-mux.h>
> +#include <linux/acpi.h>
>  #include "inv_mpu_iio.h"
>  
>  /*
> @@ -875,6 +876,13 @@ static const struct i2c_device_id inv_mpu_id[] = {
>  
>  MODULE_DEVICE_TABLE(i2c, inv_mpu_id);
>  
> +static const struct acpi_device_id inv_acpi_match[] = {
> +	{"INVN6500", 0},
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(acpi, inv_acpi_match);
> +
>  static struct i2c_driver inv_mpu_driver = {
>  	.probe		=	inv_mpu_probe,
>  	.remove		=	inv_mpu_remove,
> @@ -883,6 +891,7 @@ static struct i2c_driver inv_mpu_driver = {
>  		.owner	=	THIS_MODULE,
>  		.name	=	"inv-mpu6050",
>  		.pm     =       INV_MPU6050_PMOPS,
> +		.acpi_match_table = ACPI_PTR(inv_acpi_match),
>  	},
>  };
>  
> 

Re: [PATCH 2/3] iio: imu: inv_mpu6050: Added adapter class

[Wolfram Sang]

On Fri, Dec 26, 2014 at 12:37:36PM +0000, Jonathan Cameron wrote:
> On 15/12/14 21:19, Srinivas Pandruvada wrote:
> > To use i2c auto detect to work we need to have a non zero class.
> > The closest class is I2C_CLASS_HWMON, as it defined to be used
> > with all hw monitoring drivers.
> > 
> > Also this class is already used by some iio driver, hid drivers, led
> > and misc drivers. So this is not new that this is used outside
> > hwmon drivers.
> > 
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Been meaning to sort this out for a while.  We really shouldn't be camping
> on the HWMON class (nor should anyone else).
> 
> Wolfram, do you mind new classes being added?

In general, I wouldn't mind but I wonder if it makes sense here. DDC and
SPD are very special I2C uses where access should be limited, so a
seperate class makes sense IMO. HWMON has a specific name, but really
became "everything what people could hook to their I2C bus" these days.
So, if anything, we could think about renaming I2C_CLASS_HWMON to
I2C_CLASS_STANDARD or something (or at least add a comment about that in
i2c.h)? I'd think IIO devices fall into the default category. Please say
if you think different. If we'd add the IIO class, most drivers will
need patches to support IIO devices which would have worked otherwise,
so this change should be justified.

@Jean: Do you have anything to add?

Re: [PATCH 2/3] iio: imu: inv_mpu6050: Added adapter class

[Jonathan Cameron]

On 31/12/14 10:25, Wolfram Sang wrote:
> On Fri, Dec 26, 2014 at 12:37:36PM +0000, Jonathan Cameron wrote:
>> On 15/12/14 21:19, Srinivas Pandruvada wrote:
>>> To use i2c auto detect to work we need to have a non zero class.
>>> The closest class is I2C_CLASS_HWMON, as it defined to be used
>>> with all hw monitoring drivers.
>>>
>>> Also this class is already used by some iio driver, hid drivers, led
>>> and misc drivers. So this is not new that this is used outside
>>> hwmon drivers.
>>>
>>> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
>> Been meaning to sort this out for a while.  We really shouldn't be camping
>> on the HWMON class (nor should anyone else).
>>
>> Wolfram, do you mind new classes being added?
> 
> In general, I wouldn't mind but I wonder if it makes sense here. DDC and
> SPD are very special I2C uses where access should be limited, so a
> seperate class makes sense IMO. HWMON has a specific name, but really
> became "everything what people could hook to their I2C bus" these days.
> So, if anything, we could think about renaming I2C_CLASS_HWMON to
> I2C_CLASS_STANDARD or something (or at least add a comment about that in
> i2c.h)? I'd think IIO devices fall into the default category. Please say
> if you think different. If we'd add the IIO class, most drivers will
> need patches to support IIO devices which would have worked otherwise,
> so this change should be justified.
The I2C_CLASS_STANDARD option sounds sensible - though perhaps the comment
would be quicker ;)
> 
> @Jean: Do you have anything to add?
> 
> --
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> 

Re: [PATCH 2/3] iio: imu: inv_mpu6050: Added adapter class

[Jean Delvare]

Hi Wolfram,

First of all, happy new year :-)

On Wed, 31 Dec 2014 11:25:54 +0100, Wolfram Sang wrote:
> On Fri, Dec 26, 2014 at 12:37:36PM +0000, Jonathan Cameron wrote:
> > On 15/12/14 21:19, Srinivas Pandruvada wrote:
> > > To use i2c auto detect to work we need to have a non zero class.
> > > The closest class is I2C_CLASS_HWMON, as it defined to be used
> > > with all hw monitoring drivers.
> > > 
> > > Also this class is already used by some iio driver, hid drivers, led
> > > and misc drivers. So this is not new that this is used outside
> > > hwmon drivers.
> > > 
> > > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> > Been meaning to sort this out for a while.  We really shouldn't be camping
> > on the HWMON class (nor should anyone else).

This is correct, side effects could be quite bad.

> > Wolfram, do you mind new classes being added?
> 
> In general, I wouldn't mind but I wonder if it makes sense here. DDC and
> SPD are very special I2C uses where access should be limited, so a
> seperate class makes sense IMO. HWMON has a specific name, but really
> became "everything what people could hook to their I2C bus" these days.

HWMON is there mainly for historical reasons, which still hold due to
the inability of PC hardware vendors to list which I2C devices are
connected to the SMBus (although this is changing, ACPI could help to
some degree now.)

> So, if anything, we could think about renaming I2C_CLASS_HWMON to
> I2C_CLASS_STANDARD or something (or at least add a comment about that in
> i2c.h)? I'd think IIO devices fall into the default category. Please say
> if you think different. If we'd add the IIO class, most drivers will
> need patches to support IIO devices which would have worked otherwise,
> so this change should be justified.
> 
> @Jean: Do you have anything to add?

I2C_CLASS_STANDARD sounds like a rather bad idea to me. But really I
miss the background for the discussion so it's hard for me to make an
educated comment.

Please keep in mind that I2C_CLASS_* is not about which class I2C
devices (or even device drivers) belong to. It is about which drivers
should actively _probe_ for their devices on which I2C bus segments.
This is, in general, a bad idea and should be avoided as much as
possible, in favor of enumeration. I2C device probing is inefficient,
unreliable and dangerous by nature.

The reason why we still do it for DDC and SPD is because the range of
addresses is very limited, and probing is somewhat part of the
specification. The reason why we do it for HWMON is because enumeration
does not exist at the hardware level on popular platforms. For
everything else we have backed out (analog and digital TV, in
particular.)

So I am wondering, which platforms are using IIO drivers and do not
support device enumeration at the firmware / device tree level?

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Wolfram Sang]

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> This is odd enough, that I'd like a wider range of views on it.
> 
> Wolfram - was this the approach you had in mind?

Sorry, too busy with other stuff at this moment :(


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Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Wolfram Sang]

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> This is odd enough, that I'd like a wider range of views on it.
> 
> Wolfram - was this the approach you had in mind?

Sorry, too busy with other stuff at this moment :(


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Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2015-01-08 at 17:40 +0100, Wolfram Sang wrote: 
> > This is odd enough, that I'd like a wider range of views on it.
> > 
> > Wolfram - was this the approach you had in mind?
> 
> Sorry, too busy with other stuff at this moment :(
> 
I will find some other way without using auto detect feature.

Re: [PATCH 3/3] iio: ak8975: Added autodetect feature for ACPI

[Srinivas Pandruvada]

On Thu, 2015-01-08 at 17:40 +0100, Wolfram Sang wrote: 
> > This is odd enough, that I'd like a wider range of views on it.
> > 
> > Wolfram - was this the approach you had in mind?
> 
> Sorry, too busy with other stuff at this moment :(
> 
I will find some other way without using auto detect feature.