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

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Message-ID: <837b221d-57ad-88fb-65df-e1cae64f0ad0@gmail.com>
Date:   Thu, 21 Jan 2021 21:08:25 +0000
From:   Daniel Scally <djrscally@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     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

Hi both

On 20/01/2021 11:44, Andy Shevchenko wrote:
> On Wed, Jan 20, 2021 at 06:18:53AM +0200, Laurent Pinchart wrote:
>> On Tue, Jan 19, 2021 at 07:43:15PM +0200, Andy Shevchenko wrote:
>>> On Tue, Jan 19, 2021 at 06:36:31PM +0200, Laurent Pinchart wrote:
>>>> On Tue, Jan 19, 2021 at 11:33:58AM +0200, 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:
> ...
>
>>>>> 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.
>>>> That seems really overkill given the very simple implementation of the
>>>> clock provided here.
>>> Less code in the end is called an overkill? Hmm...
>>> I think since we in Linux it's better to utilize what it provides. Do you want
>>> me to prepare a patch to show that there is no overkill at all?
>> The amount of code we would save it very small. It's not necessarily a
>> bad idea, but I think such an improvement could be made on top, it
>> shouldn't block this series.
> Okay, let's wait what Dan will say on this.
> I can probably help to achieve this improvement sooner than later.


Well; turns out that we missed an operation we really need to add
(clk_recalc_rate) which in our case needs to read a fixed value stored
in a buffer in ACPI; most of the code is shared with an existing
function in the driver so it's not much extra to add, but I think it
kinda precludes using clk-gpio for this anyway

>>>>>> (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/)
>>>> How do you expose the link between the sensor and its indicator LED to
>>>> userspace ? Isn't it better to handle it in the kernel to avoid rogue
>>>> userspace turning the camera on without notifying the user ?
>>> I didn't get this. It's completely a LED handling driver business. We may
>>> expose it to user space or not, but it's orthogonal to the usage of LED class
>>> IIUC. Am I mistaken here?
>> If it stays internal to the kernel and is solely controlled from the
>> int3472 driver, there's no need to involve the LED class. If we want to
>> expose the privacy LED to userspace then the LED framework is the way to
>> go, but we will also need to find a way to expose the link between the
>> camera sensor and the LED to userspace. If there are two privacy LEDs,
>> one for the front sensor and one for the back sensor, userspace will
>> need to know which is which.
> I see. For now we probably can keep GPIO LED implementation internally.
>