linux-kernel - Re: [PATCH 13/22] ncr5380: Remove disused atari

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Date:	Mon, 14 Mar 2016 08:42:16 +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 13/22] ncr5380: Remove disused atari_NCR5380.c core driver

On 03/14/2016 05:27 AM, Finn Thain wrote:
> Now that atari_scsi and sun3_scsi have been converted to use the NCR5380.c
> core driver, remove atari_NCR5380.c. Also remove the last vestiges of its
> Tagged Command Queueing implementation from the wrapper drivers.
> 
> The TCQ support in atari_NCR5380.c is abandoned by this patch. It is not
> merged into the remaining core driver because,
> 
> 1) atari_scsi defines SUPPORT_TAGS but leaves FLAG_TAGGED_QUEUING disabled
> by default, which indicates that it is mostly undesirable.
> 
> 2) I'm told that it doesn't work correctly when enabled.
> 
> 3) The algorithm does not make use of block layer tags which it will have
> to do because scmd->tag is deprecated.
> 
> 4) sun3_scsi doesn't define SUPPORT_TAGS at all, yet the the SUPPORT_TAGS
> macro interacts with the CONFIG_SUN3 macro in 'interesting' ways.
> 
> 5) Compile-time configuration with macros like SUPPORT_TAGS caused the
> configuration space to explode, leading to untestable and unmaintainable
> code that is too hard to reason about.
> 
> The merge_contiguous_buffers() code is also abandoned. This was unused
> by sun3_scsi. Only atari_scsi used it and then only on TT, because only TT
> supports scatter/gather. I suspect that the TT would work fine with
> ENABLE_CLUSTERING instead. If someone can benchmark the difference then
> perhaps the merge_contiguous_buffers() code can be be justified. Until
> then we are better off without the extra complexity.
> 
> Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
> 
> ---
>  drivers/scsi/NCR5380.c       |   22 
>  drivers/scsi/NCR5380.h       |   19 
>  drivers/scsi/atari_NCR5380.c | 2632 -------------------------------------------
>  drivers/scsi/atari_scsi.c    |   11 
>  drivers/scsi/mac_scsi.c      |    8 
>  drivers/scsi/sun3_scsi.c     |   11 
>  6 files changed, 4 insertions(+), 2699 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@...e.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@...e.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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