linux-kernel - Re: [PATCH v2 6/7] platform: x86: Add intel_skl

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Message-ID: <b01e1439-d503-2989-5769-971d75c1cae6@gmail.com>
Date:   Tue, 19 Jan 2021 09:34:10 +0000
From:   Daniel Scally <djrscally@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, devel@...ica.org,
        rjw@...ysocki.net, lenb@...nel.org, andy@...nel.org,
        mika.westerberg@...ux.intel.com, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, wsa@...nel.org, lee.jones@...aro.org,
        hdegoede@...hat.com, mgross@...ux.intel.com,
        robert.moore@...el.com, erik.kaneda@...el.com,
        sakari.ailus@...ux.intel.com, kieran.bingham@...asonboard.com
Subject: Re: [PATCH v2 6/7] platform: x86: Add intel_skl_int3472 driver

Morning Andy

On 19/01/2021 09:33, Andy Shevchenko wrote:
> On Tue, Jan 19, 2021 at 12:11:40AM +0000, Daniel Scally wrote:
>> On 18/01/2021 21:19, Daniel Scally wrote:
>> I'm more and more confident that this will work, but it has some
>> knock-on effects:
>>
>> The both clk and regulator gpio driver expects to be able to fetch the
>> GPIO using devm_gpiod_get(&pdev->dev, "enable", ...). That won't work of
>> course, so we need to add another GPIO lookup table so those drivers can
>> see the GPIOs. For that, we need to know what dev_name(&pdev->dev) will
>> be so we can set the .dev_id member of a gpiod_lookup_table to that
>> value, but that isn't set until _after_ the pdev is registered (because
>> it has to figure out the id, we can't manually set the IDs because there
>> could be more than one instance of int3472-discrete bound to multiple
>> PMIC devices, and we don't know which id the current one should have).
>> Finally, we can't wait until the device is registered because it
>> immediately probes, can't find the GPIO and then fails probe.
>>
>> It's similar problem that causes us to need the i2c-acpi name format
>> macros, but complicated by the dynamic ID part of dev_name(&pdev->dev)
>>
>> Solving it is a bit of a sticky one; perhaps something like moving the
>> dev_set_name() part of platform_device_add() [1] to its own function,
>> that's called in both platform_device_alloc() and
>> platform_device_register(). That way it would be available before the
>> device itself was registered, meaning we could create the lookup table
>> before it probes the driver.
> See my previous reply. TL;DR: you have to modify clk-gpio.c to export couple of
> methods to be able to use it as a library.


Ack! Ok, I thought about that the wrong way. I'll take another look
tonight then.


>> (also, Laurent, if we did it this way we wouldn't be able to also handle
>> the led-indicator GPIO here without some fairly major rework)
> LED indicators are done as LED class devices (see plenty of examples in PDx86
> drivers: drivers/platform/x86/)
And this too - thanks very much