linux-kernel - Re: [PATCH 2/2] drivers: iio: accel adxl312 and adxl314 support

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Date:   Tue, 16 Aug 2022 16:34:59 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     George Mois <george.mois@...log.com>, jic23@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, lucas.p.stankus@...il.com
Subject: Re: [PATCH 2/2] drivers: iio: accel adxl312 and adxl314 support

On 16/08/2022 15:44, Jonathan Cameron wrote:
>>>  
>>>  MODULE_DEVICE_TABLE(spi, adxl313_spi_id);
>>>  
>>>  static const struct of_device_id adxl313_of_match[] = {
>>> +	{ .compatible = "adi,adxl312" },
>>>  	{ .compatible = "adi,adxl313" },
>>> +	{ .compatible = "adi,adxl314" },  
>>
>> You miss here driver data. I don't remember which driver matching takes
>> precedence (especially in various cases like DT platforms with device
>> instantiated by MFD), but for consistency I think both device id tables
>> should have same driver data.
> 
> You can set it up to try device_get_match_data() first then fallback
> to the adxl313_spi_id[] table but there isn't a nice 'standard' way to
> do it.
> 
> If that isn't done, then IIRC the match is against the compatible with
> the vendor ID dropped and the table used is the spi_device_id one.
> Which is just annoyingly complex and relies on the strings matching.
> 
> In the ideal world the spi_device_id table would go away but there are
> still a few users (greybus - I think + remaining board files).
> So for now something like
> 
> a = device_get_match_data(dev);
> if (!a)
> 	a = &adxl31x_spi_regmap_config[id->data];
> 
> Provides a good way of ensuring the id tables don't need to remain
> in sync.
> 

I guess the only minor issue is that first driver data - ADXL312 - is
equal to 0, so above code would make consider ADXL312 as missing data.

Best regards,
Krzysztof