From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH v3] libsas: move ATA bits into a separate module Date: Thu, 14 Sep 2006 18:49:51 -0400 Message-ID: <4509DC8F.6030900@garzik.org> References: <4508A0A2.2080605@us.ibm.com> <450971D3.2040405@garzik.org> <4509DA77.7000508@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4509DA77.7000508@us.ibm.com> Sender: linux-scsi-owner@vger.kernel.org To: "Darrick J. Wong" Cc: linux-ide , linux-scsi , Linux Kernel Mailing List , Alexis Bruemmer , Mike Anderson , James Bottomley List-Id: linux-ide@vger.kernel.org Darrick J. Wong wrote: > Jeff Garzik wrote: > >> I disagree completely with this approach. >> >> You don't need a table of hooks for the case where libata is disabled in >> .config. Thus, it's only useful for the case where libsas is loaded as >> a module, but libata is not. > > Indeed, I misunderstood what James Bottomley wanted, so I reworked the > patch. It has the same functionality as before, but this module uses > the module loader/symbol resolver for all the functions in libata, and > allows libsas to (optionally) call into sas_ata with weak references by > pushing a table of the necessary function pointers into libsas at > sas_ata load time. Thus, libsas doesn't need to load libata/sas_ata > unless it actually finds a SATA device. > >> The libsas code should directly call libata functions. If ATA support >> in libsas is disabled in .config, then those functions will never be >> called, thus never loaded the libata module. > > I certainly can (and now do) call libata functions from sas_ata. > However, there are a few cases where libsas needs to call libata (ex. > sas_ioctl); for those cases, I think the function pointers are still > necessary because I don't want to make libsas require libata. In any > case, if ATA support is disabled in .config, sata_is_dev always returns > 0, so the dead-code eliminator should zap that out of libsas entirely. Looks MUCH better to me, and eliminates my objection to the libata-related hooks. There remains the issue that I poke James about on IRC, namely that there is no need to emulate the SATA phy registers. libata permits a driver high level access to the ATA engine without needing SATA SCRs. Witness all the PATA drivers, which obviously do not have SCRs at all. Jeff