linux-kernel - Re: [PATCH 01/22] g_ncr5380: Remove CONFIG_SCSI_GENERIC

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Date:	Mon, 14 Mar 2016 08:21:07 +0100
From:	Hannes Reinecke <hare@...e.de>
To:	Finn Thain <fthain@...egraphics.com.au>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Michael Schmitz <schmitzmic@...il.com>,
	linux-m68k@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	Ondrej Zary <linux@...nbow-software.org>,
	Sam Creasey <sammy@...my.net>
Subject: Re: [PATCH 01/22] g_ncr5380: Remove CONFIG_SCSI_GENERIC_NCR53C400

On 03/14/2016 05:27 AM, Finn Thain wrote:
> This change brings a number of improvements: fewer macros, better test
> coverage, simpler code and sane Kconfig options. The downside is a small
> chance of incompatibility (which seems unavoidable).
> 
> CONFIG_SCSI_GENERIC_NCR53C400 exists to enable or inhibit pseudo DMA
> transfers when the driver is used with 53C400-compatible cards. Thanks to
> Ondrej Zary's patches, PDMA now works which means it can be enabled
> unconditionally.
> 
> Due to bad design, CONFIG_SCSI_GENERIC_NCR53C400 ties together unrelated
> functionality as it sets both PSEUDO_DMA and BIOSPARAM macros. This patch
> effectively enables PSEUDO_DMA and disables BIOSPARAM.
> 
> The defconfigs and the Kconfig default leave CONFIG_SCSI_GENERIC_NCR53C400
> undefined. Red Hat 9 and CentOS 2.1 were the same. This leaves both
> PSEUDO_DMA and BIOSPARAM disabled. The effect of this patch should be
> better performance from enabling PSEUDO_DMA.
> 
> On the other hand, Debian 4 and SLES 10 had CONFIG_SCSI_GENERIC_NCR53C400
> enabled, so both PSEUDO_DMA and BIOSPARAM were enabled. This patch might
> affect configurations like this by disabling BIOSPARAM. My best guess is
> that this could be a problem only in the vanishingly rare case that
> 1) the CHS values stored in the boot device partition table are wrong and
> 2) a 5380 card is in use (because PDMA on 53C400 used to be broken).
> 
> Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
> 
> ---
> 
Reviewed-by: Hannes Reinecke <hare@...e.com>

And don't worry about SLES10; we won't backport your fixes to _that_.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@...e.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)