linux-kernel - Re: [PATCH 1/4] Introduce ata_id_has

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Message-ID: <48B9357A.3040508@ru.mvista.com>
Date:	Sat, 30 Aug 2008 15:56:42 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Elias Oltmanns <eo@...ensachen.de>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Jeff Garzik <jeff@...zik.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Tejun Heo <htejun@...il.com>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] Introduce ata_id_has_unload()

Hello.

Elias Oltmanns wrote:

> Add a function to check an ATA device's id for head unload support as
> specified in ATA-7.
>
> Signed-off-by: Elias Oltmanns <eo@...ensachen.de>
>   
[...]
> diff --git a/include/linux/ata.h b/include/linux/ata.h
> index 80364b6..d9a94bd 100644
> --- a/include/linux/ata.h
> +++ b/include/linux/ata.h
> @@ -707,6 +707,23 @@ static inline int ata_id_has_dword_io(const u16 *id)
>  	return 0;
>  }
>  
> +static inline int ata_id_has_unload(const u16 *id)
> +{
> +	/*
> +	 * ATA-7 specifies two places to indicate unload feature
> +	 * support. Since I don't really understand the difference,
> +	 * I'll just check both and only return zero if none of them
> +	 * indicates otherwise.
>   

   If you read the comments to the words 82:84 and 85:87, they say that 
the former indicate the supported features, and the latter indicate the 
enabed features AND in case a feature can't be disabled, the latter 
words will have the corresponding bit set. So it should be sufficient to 
check only one word.

> +	 */
> +	if (ata_id_major_version(id) >= 7
> +	    && (((id[ATA_ID_CFSSE] & 0xC000) == 0x4000
> +		 && id[ATA_ID_CFSSE] & (1 << 13))
> +		|| ((id[ATA_ID_CSF_DEFAULT] & 0xC000) == 0x4000
> +		    && (id[ATA_ID_CSF_DEFAULT] & (1 << 13)))))
>   


   I think that it's preferrable to leave the operator on the same line 
with the first operand...

WBR, Sergei


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