[Intel-gfx] [PATCH v8 1/2] ACPI / bus: Introduce a list of ids for "always present" devices

[Hans de Goede]

Hi,

On 21-04-17 13:38, Andy Shevchenko wrote:
> On Fri, 2017-04-21 at 12:47 +0200, Hans de Goede wrote:
>> Several Bay / Cherry Trail devices (all of which ship with Windows 10)
>> hide
>> the LPSS PWM controller in ACPI, typically the _STA method looks like
>> this:
>>
>>      Method (_STA, 0, NotSerialized)  // _STA: Status
>>      {
>>          If (OSID == One)
>>          {
>>              Return (Zero)
>>          }
>>
>>          Return (0x0F)
>>      }
>>
>> Where OSID is some dark magic seen in all Cherry Trail ACPI tables
>> making
>> the machine behave differently depending on which OS it *thinks* it is
>> booting, this gets set in a number of ways which we cannot control, on
>> some newer machines it simple hardcoded to "One" aka win10.
>>
>> This causes the PWM controller to get hidden, which means Linux cannot
>> control the backlight level on cht based tablets / laptops.
>>
>> Since loading the driver for this does no harm (the only in kernel
>> user
>> of it is the i915 driver, which will only uses it when it needs it),
>> this
>> commit makes acpi_bus_get_status() always set status to
>> ACPI_STA_DEFAULT
>> for the LPSS PWM device, fixing the lack of backlight control.
>>
> 
>>   drivers/acpi/Makefile        |  1 +
>>   drivers/acpi/bus.c           |  5 +++
>>   drivers/acpi/x86/x86_utils.c | 85
>> ++++++++++++++++++++++++++++++++++++++++++++
> 
> Perhaps .../x86/utils.c ?

I thought that utils.c would be too generic,
but that was mainly thinking about module kernel
cmdline options which do not apply here, still
having a somewhat unique basename seems useful.

> 
>>   include/acpi/acpi_bus.h      |  9 +++++
> 
>> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
>> index 34fbe02..784bda6 100644
>> --- a/drivers/acpi/bus.c
>> +++ b/drivers/acpi/bus.c
>> @@ -114,6 +114,11 @@ int acpi_bus_get_status(struct acpi_device
>> *device)
>>   	acpi_status status;
>>   	unsigned long long sta;
>>   
>> +	if (acpi_device_always_present(device)) {
>> +		acpi_set_device_status(device, ACPI_STA_DEFAULT);
>> +		return 0;
>> +	}
>> +
>>   	status = acpi_bus_get_status_handle(device->handle, &sta);
>>   	if (ACPI_FAILURE(status))
>>   		return -ENODEV;
>>
> 
>> +#define ICPU(model)	{ X86_VENDOR_INTEL, 6, model,
>> X86_FEATURE_ANY, }
>> +
> 
>> +#define ENTRY(hid, uid, cpu_models) {				
> 
> cpu_models -> cpu_model ?
> 
> Or I missed that it's an array?

It may be an array, e.g. :

         ENTRY("INT0002", "1", (ICPU(INTEL_FAM6_ATOM_SILVERMONT1), ICPU(INTEL_FAM6_ATOM_AIRMONT)) ),

Note this is a theoretical example (for now).

Regards,

Hans