linux-kernel - Re: [patch 1/2] Enable link power management for ata drivers

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Message-ID: <46F84F45.6000807@pobox.com>
Date:	Mon, 24 Sep 2007 19:59:01 -0400
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Kristen Carlson Accardi <kristen.c.accardi@...el.com>
CC:	roel <12o3l@...cali.nl>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Alan <alan@...rguk.ukuu.org.uk>
Subject: Re: [patch 1/2] Enable link power management for ata drivers

Kristen Carlson Accardi wrote:
> On Tue, 25 Sep 2007 01:12:32 +0200
> roel <12o3l@...cali.nl> wrote:
> 
>>>  #define ata_id_cdb_intr(id)	(((id)[0] & 0x60) == 0x20)
>>> +#define ata_id_has_hipm(id)	\
>>> +	( (((id)[76] != 0x0000) && ((id)[76] != 0xffff)) && \
>>> +	  ((id)[76] & (1 << 9)) )
>> 		^
>> 		|
>> are you sure this
>> should be 76?
> 
> Yes.
> 
>> we can also change the first statement a bit:
>> 	(!(((id)[76] == 0x0000) || ((id)[76] == 0xffff)) && \
>>
>>
>>> +#define ata_id_has_dipm(id)	\
>>> +	( (((id)[76] != 0x0000) && ((id)[76] != 0xffff)) && \
>> and:
>> 	(!(((id)[76] == 0x0000) || ((id)[76] == 0xffff)) && \
> 
> I feel this is equivalent functionality and not as readable.

Poke around for Alan Cox's cleanup of this area of linux/ata.h.

It converts several macros to inline functions (encouraged), and also 
illustrates a nice, clean way of testing an ID word's validity. 
[obviously the final implementation varies, depending on that ID word's 
history]

Alan or Andrew, got a copy somewhere?  My feeble search skills don't 
seem to turn it up at the moment, even though I had a copy in my hands 
quite recently.

	Jeff


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