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

[Jonathan Cameron <jic23@kernel.org>]

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
>>
> 
>