linux-kernel - Re: [PATCH][drivers/misc/thinkpad_acpi.c] duplicate test if (level & TP_EC_FAN

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Date:	Thu, 07 Feb 2008 00:48:24 +0100
From:	Roel Kluin <12o3l@...cali.nl>
To:	Greg KH <greg@...ah.com>
CC:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Roland Dreier <rdreier@...co.com>, len.brown@...el.com,
	ibm-acpi-devel@...ts.sourceforge.net, linux-acpi@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, stable@...nel.org
Subject: Re: [PATCH][drivers/misc/thinkpad_acpi.c] duplicate test if (level
 & TP_EC_FAN_FULLSPEED)

Greg KH wrote:
> On Tue, Feb 05, 2008 at 09:34:54AM +0100, Roel Kluin wrote:
>> Henrique de Moraes Holschuh wrote:
>>> On Tue, 05 Feb 2008, Roel Kluin wrote:
>>>> Roland Dreier wrote:

>>>>>  > Note the duplicate test 'if (level & TP_EC_FAN_FULLSPEED)'. should
>>>>>  > this be replaced by
>>>>>
>>>>> Actually I suspect one of the two tests should be against TP_EC_FAN_AUTO
>>>>> (based on the comment).
>>>> Thanks Roland, for your info

>>> ACK.  This needs to be sent to stable as well.  I think both 2.6.22 and
>>> 2.6.23 need this patch.
>>>
>> CC stable@...nel.org
> 
> Please send us a real copy of the patch, when it goes into Linus's tree,
> so we know what to apply, and that it is safe to do so.

It's a oneliner and the patch is from linus' tree.
---
in commit eaa7571b2d1a08873e4bdd8e6db3431df61cd9ad, a safety net for TPEC
fan control mode was added. Quoting that patch:

"The Linux ThinkPad community is not positive that all ThinkPads that do
HFSP EC fan control do implement full-speed and auto modes, some of the
earlier ones supporting HFSP might not.

If the EC ignores the AUTO or FULL-SPEED bits, it will pay attention to the
lower three bits that set the fan level. And as thinkpad-acpi was leaving
these set to zero, it would stop(!) the fan, which is Not A Good Thing.
So, as a safety net, we now make sure to also set the fan level part of the
HFSP register to speed 7 for full-speed, and a minimum of speed 4 for auto
mode."

However, in the section below the test for the FULL-SPEED bits was not added:
the AUTO bits were tested twice. This patch corrects this and ensures that
the fan level part of the  HFSP register is set to a minimum of speed 4 for
auto mode.

Signed-off-by: Roel Kluin <12o3l@...cali.nl>
---
diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index cf56647..3c323fe 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -4138,7 +4138,7 @@ static int fan_set_level(int level)
 		 * or FULLSPEED mode bits and just ignore them */
 		if (level & TP_EC_FAN_FULLSPEED)
 			level |= 7;	/* safety min speed 7 */
-		else if (level & TP_EC_FAN_FULLSPEED)
+		else if (level & TP_EC_FAN_AUTO)
 			level |= 4;	/* safety min speed 4 */
 
 		if (!acpi_ec_write(fan_status_offset, level))

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