linux-kernel - RE: [PATCH v3 3/5] drivers: regulator: Add ADI MAX77541/MAX77540 Regulator Support

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Date:   Tue, 31 Jan 2023 13:59:45 +0000
From:   "Sahin, Okan" <Okan.Sahin@...log.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC:     Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        ChiYuan Huang <cy_huang@...htek.com>,
        "Bolboaca, Ramona" <Ramona.Bolboaca@...log.com>,
        Caleb Connolly <caleb.connolly@...aro.org>,
        William Breathitt Gray <william.gray@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>
Subject: RE: [PATCH v3 3/5] drivers: regulator: Add ADI MAX77541/MAX77540
 Regulator Support

On Tue, 31 Jan 2022 4:30 PM
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

>On Tue, Jan 31, 2023 at 01:23:33PM +0000, Sahin, Okan wrote:
>> On Tue, 31 Jan 2022 3:27 PM
>> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
>> >On Tue, Jan 31, 2023 at 09:27:48AM +0000, Sahin, Okan wrote:
>
>...
>
>> >> Sorry for second question. I do not want to bother you, but I
>> >> realized that I need to be sure about driver_data before sending
>> >> new patch. You said that you need to use pointers directly for
>> >> driver_data then I fixed that part in mfd, but I do not need or
>> >> use driver_data in regulator since chip_id comes from mfd device so
>> >> I think using like below should be enough for my implementation.
>> >>
>> >> static const struct platform_device_id max77541_regulator_platform_id[] =
>{
>> >> 	{ "max77540-regulator", },
>> >> 	{ "max77541-regulator", },
>> >> 	{  /* sentinel */  }
>> >> };
>> >> MODULE_DEVICE_TABLE(platform, max77541_regulator_platform_id);
>> >>
>> >> static const struct of_device_id max77541_regulator_of_id[] = {
>> >> 	{ .compatible = "adi,max77540-regulator", },
>> >> 	{ .compatible = "adi,max77541-regulator", },
>> >> 	{ /* sentinel */  }
>> >> };
>> >> MODULE_DEVICE_TABLE(of, max77541_regulator_of_id);
>> >>
>> >> What do you think?
>> >
>> >If you have got all necessary data from the upper layer, why do you
>> >need to have an ID table here? I'm not sure I understand how this OF
>> >ID table works in this case.
>
>> I added it since there is regulator node in device tree. With the help
>> of devm_regulator_register(..), driver takes parameters of regulator
>> node. I also used id to select and to initialize regulator descriptors
>> which are chip specific. So far there is no comment about OF ID table
>> so I kept it. I thought I need to add both of id table and platform id
>> table as name matching is required to initialize platform device from mfd.
>
>For platform device is one mechanism how to enumerate device, and bind it to
>the driver. The OF ID table needs to be present in case you are using it for direct
>DT enumeration (there is also something related to MFD child nodes, but you
>need to check and explain how your device is enumerated by this driver).
>
>I.o.w. please clarify how the OF ID table is being used.
>
>--
>With Best Regards,
>Andy Shevchenko
>

Hi Andy,

I do not use "of id table" directly in max77541-regulator.c so do I need to exclude it?
However, devm_regulator_register(..) method initialize each regulator with the nodes under "regulators node". If of_match in desc and name of node matches, then regulator will be initialized with parameters in the node under the regulators node in the device tree. Since I am using device tree to initialize regulators, I added of id table. I hope I explained the situation clearly. 

Regards,
Okan Sahin