Re: [PATCH v6] platform/x86: Add driver for ACPI WMAA EC-based backlight control

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 9/21/21 4:29 PM, Daniel Dadap wrote:
> 
>> On Sep 21, 2021, at 08:53, Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Hi,
>>
>>> On 9/20/21 3:51 PM, Pali Rohár wrote:
>>>> On Monday 20 September 2021 15:33:20 Hans de Goede wrote:
>>>> Hi Pali,
>>>>
>>>> On 9/20/21 3:29 PM, Pali Rohár wrote:
>>>>> On Monday 13 September 2021 11:01:50 Hans de Goede wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On 9/3/21 2:38 AM, Daniel Dadap wrote:
>>>>>>> A number of upcoming notebook computer designs drive the internal
>>>>>>> display panel's backlight PWM through the Embedded Controller (EC).
>>>>>>> This EC-based backlight control can be plumbed through to an ACPI
>>>>>>> "WMAA" method interface, which in turn can be wrapped by WMI with
>>>>>>> the GUID handle 603E9613-EF25-4338-A3D0-C46177516DB7.
>>>>>>>
>>>>>>> Add a new driver, aliased to the WMAA WMI GUID, to expose a sysfs
>>>>>>> backlight class driver to control backlight levels on systems with
>>>>>>> EC-driven backlights.
>>>>>>>
>>>>>>> Signed-off-by: Daniel Dadap <ddadap@nvidia.com>
>>>>>>> Reviewed-By: Thomas Weißschuh <linux@weissschuh.net>
>>>>>>
>>>>>> Thank you for your patch, I've applied this patch to my review-hans 
>>>>>> branch:
>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=review-hans
>>>>>>
>>>>>> Note it will show up in my review-hans branch once I've pushed my
>>>>>> local branch there, which might take a while.
>>>>>>
>>>>>> Once I've run some tests on this branch the patches there will be
>>>>>> added to the platform-drivers-x86/for-next branch and eventually
>>>>>> will be included in the pdx86 pull-request to Linus for the next
>>>>>> merge-window.
>>>>>
>>>>> Hello Hans!
>>>>>
>>>>> I would suggest to rename this driver and config option to not include
>>>>> -AA in its name. WMAA is just internal name of ACPI method, composed
>>>>> from two parts: "WM" and "AA". Second part "AA" is read from the _WDG
>>>>> where is the translation table from WMI GUID (in this case 603E9613...)
>>>>> to ACPI method name. "AA" is just autogenerated identifier by wmi
>>>>> compiler and because names are ASCII strings, I guess "AA" could mean
>>>>> the first (autogenerated) method. In the whole driver code you are not
>>>>> using AA function name, but directly WMI GUID, which also means that
>>>>> driver is prepared if vendor "recompiles" wmi code in acpi (and compiler
>>>>> generates another identifier, not AA). Also another argument is that
>>>>> there can be lot of other laptops which have WMAA ACPI method but they
>>>>> can have different API or do something totally different. So name WMAA
>>>>> is in this wmi context very misleading. Rather it should be named by
>>>>> vendor.
>>>>
>>>> Right, that is a very valid point. I should have spotted this myself.
>>>>
>>>> So what would be a better name wmi-nvidia-backlight.ko I guess ?
>>>> (and update the rest to match ?)
>>>
>>> It looks like that no vendor driver starts with "wmi-" prefix. "-wmi"
>>> string is used as a suffix. So for consistency it would be better to
>>> choose "nvidia-backlight-wmi.ko".
>>
>> Right, I should have checked first.
>>
>> So I just checked and the standard pattern used is:
>> vendor_wmi_feature
>>
>> So lets go with nvidia_wmi_backlight.ko
>>
>> Daniel, can you prepare a patch on top of your merged patch to do
>> the rename of the Kconfig entry and the module-name please?
>>
> 
> Yes, I already had a patch prepared to rename things to nvidia-backlight-wmi; I am waiting to hear back from some folks if there’s a more specific name that might be appropriate (e.g. a name of a particular feature tied to this) or if it should be more generic (e.g., if there is a strong possibility this design may be used in systems with no NVIDIA GPU); while I’m waiting for those answers, I’ll switch to nvidia-wmi-backlight as the assumed option, if there isn’t something more appropriate.

Ok, sounds good, thank you.

Regards,

Hans