linux-kernel - Re: [PATCH] iio: accel: bmc150: Add OF device ID table

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Date:   Mon, 4 Dec 2017 10:36:34 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     Hartmut Knaack <knaack.h@....de>, linux-iio@...r.kernel.org,
        Lars-Peter Clausen <lars@...afoo.de>,
        Jonathan Cameron <jic23@...nel.org>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>
Subject: Re: [PATCH] iio: accel: bmc150: Add OF device ID table

Hi,

On 04-12-17 10:01, Javier Martinez Canillas wrote:
> Hi Hans,
> 
> Thanks a lot for your feedback.
> 
> On 12/04/2017 09:29 AM, Hans de Goede wrote:
>> Hi,
>>
>> On 01-12-17 12:10, 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>.
>>>
>>> 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 I2C device ID table entries have the .driver_data field set, but they
>>> are not used in the driver so weren't set in the OF device table entries.
>>>
>>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>>> ---
>>>
>>>    drivers/iio/accel/bmc150-accel-i2c.c | 12 ++++++++++++
>>>    1 file changed, 12 insertions(+)
>>>
>>> diff --git a/drivers/iio/accel/bmc150-accel-i2c.c b/drivers/iio/accel/bmc150-accel-i2c.c
>>> index f85014fbaa12..8ffc308d5fd0 100644
>>> --- a/drivers/iio/accel/bmc150-accel-i2c.c
>>> +++ b/drivers/iio/accel/bmc150-accel-i2c.c
>>> @@ -81,9 +81,21 @@ static const struct i2c_device_id bmc150_accel_id[] = {
>>>    
>>>    MODULE_DEVICE_TABLE(i2c, bmc150_accel_id);
>>>    
>>> +static const struct of_device_id bmc150_accel_of_match[] = {
>>> +	{ .compatible = "bosch,bmc150_accel" },
>>> +	{ .compatible = "bosch,bmi055_accel" },
>>
>> These look a bit weird, there is no reason to mirror the i2c_device_ids
> 
> The reason why I changed this is to make sure that module auto-loading will not
> regress after the following patch is merged:
> 
> https://patchwork.kernel.org/patch/10089425/
> 
> It's true that only DT nodes with compatible "bosch,bma250" and "bosch,bma250e"
> are used in Device Tree source files in mainline, but I didn't know if others
> could be used by out-of-tree DTB.
> 
>> here and typically for devicetree / of we only list
>> the chip model without some postfix like _accel.
>>
> 
> Right, I also wondered about that, but then I saw that there's a DT binding for
> another chips with the same model but a different function ("bosch,bmc150_magn").
> 
> Documentation/devicetree/bindings/iio/magnetometer/bmc150_magn.txt
> 
> So I thought it could be a convention for bosch chips.

Ah good point, at least for the bcm150 which really is a cluster of i2c chips
at different addresses the postfix does make sense, you're right.

>> Also if you're doing this you should probably add a:
>> Documentation/devicetree/bindings/iio/accel/bmc150.txt
>> file documenting the compatible strings, and Cc:
>> devicetree@...r.kernel.org for the next version,
>> so that the devicetree maintainers get a chance to review
>> this.
>>
> 
> Indeed, sorry for missing that. I posted patches for several drivers so I forgot
> to add the DT binding docs. My main goal was just to prevent the driver to use
> the I2C device table to match the driver when the devices are registered via OF
> and to have proper OF module aliases in the driver module so udev could autoload
> the module.
> 
> I preferred someone familiar with the device to write the DT binding document.

Ok and I see this has already be merged, which is fine by me, so lets just
keep this as is for now :)

Regards,

Hans



> 
>>> +	{ .compatible = "bosch,bma255" },
>>> +	{ .compatible = "bosch,bma250e" },
>>> +	{ .compatible = "bosch,bma222e" },
>>> +	{ .compatible = "bosch,bma280" },
>>> +	{ },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, bmc150_accel_of_match);
>>> +
>>>    static struct i2c_driver bmc150_accel_driver = {
>>>    	.driver = {
>>>    		.name	= "bmc150_accel_i2c",
>>> +		.of_match_table = bmc150_accel_of_match,
>>>    		.acpi_match_table = ACPI_PTR(bmc150_accel_acpi_match),
>>>    		.pm	= &bmc150_accel_pm_ops,
>>>    	},
>>>
>>
>> Otherwise looks good to me,
>>
>> Regards,
>>
>> Hans
>>
> 
> Best regards,
>