linux-kernel - Re: [PATCH] PNPACPI: Enable PNPACPI

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Date:	Tue, 31 Mar 2009 22:37:23 +0200
From:	Witold Szczeponik <Witold.Szczeponik@....net>
To:	yakui_zhao <yakui.zhao@...el.com>
CC:	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"bjorn.helgaas@...com" <bjorn.helgaas@...com>,
	"abelay@....edu" <abelay@....edu>, "rjw@...k.pl" <rjw@...k.pl>
Subject: Re: [PATCH] PNPACPI: Enable PNPACPI _PSx Support, v3

yakui_zhao wrote:

>     Very good patch.
>     Do you have the hardware on which the dedicated power source is
> required by the serial port(PnP device) in your hand?
> 

Yes, I have an IBM ThinkPad 600E. I need this patch in order to
be able receive accurate time using a DCF77 receiver attached
to the serial port.

[snip]

>> -	if (ACPI_FAILURE(status))
>> +	if (ACPI_FAILURE(acpi_set_current_resources(handle, &buffer)))
>>   		ret = -EINVAL;
>> +	else if (acpi_bus_power_manageable(handle))
>> +		ret = acpi_bus_set_power(handle, ACPI_STATE_D0);
> How about changing the power state before calling _SRS object?

I recall reading something in the ACPI spec that says that the power
needs to be set after the device was enabled.  But the main driver
for this order (_SRS followed by _PS0) is the symmetry to the required
_PS3 followed by _DIS (according to the spec).

[snip]

--- Witold
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