Re: [linux-pm] [PATCH 7/8] ACPI / PCI: Do not preserve _OSC control bits returned by a query (v2)

[Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>]

(2010/08/04 21:15), Rafael J. Wysocki wrote:
> On Wednesday, August 04, 2010, Kenji Kaneshige wrote:
>> (2010/08/04 17:43), Hidetoshi Seto wrote:
>>>   /**
>>>    * acpi_pci_osc_control_set - commit requested control to Firmware
>>>    * @handle: acpi_handle for the target ACPI object
>>> @@ -411,14 +379,17 @@ acpi_status acpi_pci_osc_control_query(acpi_handle handle, u32 *mask)
>>>    *
>>>    * Attempt to take control from Firmware on requested control bits.
>>>    **/
>>
>> Updating description of this function would be appreciated.

OK, I will do it.

>>> @@ -452,7 +427,10 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 flags)
>>>   	capbuf[OSC_CONTROL_TYPE] = root->osc_control_set | control_req;
>>>   	status = acpi_pci_run_osc(handle, capbuf,&result);
>>>   	if (ACPI_SUCCESS(status))
>>> -		root->osc_control_set = result;
>>> +		root->osc_control_set = *flags = result;
>>
>> I don't think we need to update *flags here, though it depends on the design
>> of this function interface.
>> IMHO, updating *flags only when AE_SUPPORT is returned is easy to understand.
> 
> I think the patch is correct.  We should update *flags in any case so that the
> caller can check what's the full mask of granted controls even if it asked for
> fewer control bits.

My idea (that will be what I'll add to the description of function) is:

  On success, OS takes all of requested control(s) and *flags is updated with
  set of controls now OS have.
  If AE_SUPPORT returns, none of control settings are changed since Firmware
  rejects granting some of requested controls. *flags is updated with set of
  controls with rejected bits cleared.
  All other cases mean failure, none of control settings are changed, and
  *flags is unchanged.

Thanks,
H.Seto