linux-kernel - Re: [PATCH] platform/x86: intel_cht_int33fe: Work around BIOS bug on some devices

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Message-ID: <6e064337-6105-2231-a66e-ccb6aba3440a@redhat.com>
Date:   Fri, 1 Sep 2017 23:58:55 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: intel_cht_int33fe: Work around BIOS bug on
 some devices

Hi,

On 09/01/2017 11:19 AM, Mika Westerberg wrote:
> On Thu, Aug 31, 2017 at 07:04:46PM +0300, Andy Shevchenko wrote:
>> On Mon, Aug 14, 2017 at 11:52 PM, Hans de Goede <hdegoede@...hat.com> wrote:
>>> On 14-08-17 22:45, Andy Shevchenko wrote:
>>>> On Mon, Aug 14, 2017 at 11:14 PM, Hans de Goede <hdegoede@...hat.com>
>>>> wrote:
>>
>>>>> +int cht_int33fe_check_for_max17047(struct device *dev, void *data)
>>>>> +{
>>>>> +       const char *name = dev_name(dev);
>>>>> +       struct i2c_client **max17047 = data;
>>>>> +
>>>>> +       if (name && strcmp(name, "i2c-MAX17047:00") == 0) {
>>>>
>>>>
>>>> Can we stop using bad practice of comparing against _instance_?
>>>> If device is suppose to be single in the system, wouldn't _HID be enough?
>>
>>> Yes _HID would be enough, but that takes some extra code with little
>>> gain IMHO, we are effectively checking the HID here as that is where
>>> the device-name comes from.
>>>
>>> Anyways if you strongly prefer a HID check I can do a v2 doing that
>>> either way let me know.
>>
>> Currently we have the following modules where ACPI instance is used in:
>>
>> drivers/acpi/acpi_lpss.c
>> drivers/input/touchscreen/goodix.c
>> drivers/platform/x86/silead_dmi.c
>> drivers/power/supply/axp288_charger.c
>>
>> and plenty under sound/soc/intel.
>>
>> I do not care right now about sound/soc/intel stuff, while everywhere
>> else would be better to avoid this.
>>
>> Mika, Rafael, what're yours opinions regarding to use ACPI instances
>> in the drivers?
> 
> Since the instance name is generated by the ACPI core and in theory
> could change, I agree this is pretty fragile. Using _HID/_UID should be
> the preferred way. However, it is not always possible so we end up doing
> hacks like this.

Given that on the device in question where we need this workaround there
is only ever 1 max17047, including the instance number in the check really
is a non-problem, but if there is a strong preference for me to change
the check over to a _HID check then I can do a v2 doing so.

Regards,

Hans