From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: [PATCH 13/18] ide: use ->tf_load in SELECT_DRIVE() Date: Tue, 17 Feb 2009 15:43:21 +0100 Message-ID: <200902171543.21892.bzolnier@gmail.com> References: <20080620213323.13202.71450.sendpatchset@localhost.localdomain> <200902162251.49271.bzolnier@gmail.com> <499A0D0B.7070007@ru.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from fg-out-1718.google.com ([72.14.220.155]:60668 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751318AbZBQPJn (ORCPT ); Tue, 17 Feb 2009 10:09:43 -0500 In-Reply-To: <499A0D0B.7070007@ru.mvista.com> Content-Disposition: inline Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Sergei Shtylyov Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org On Tuesday 17 February 2009, Sergei Shtylyov wrote: > Hello. > > Bartlomiej Zolnierkiewicz wrote: > > On Monday 16 February 2009, Sergei Shtylyov wrote: > > > >> Hello, I wrote: > >> > >> > >>>>> There should be no functional changes caused by this patch. > >>>>> Signed-off-by: Bartlomiej Zolnierkiewicz > >>>>> Index: b/drivers/ide/ide-iops.c > >>>>> =================================================================== > >>>>> --- a/drivers/ide/ide-iops.c > >>>>> +++ b/drivers/ide/ide-iops.c > >>>>> @@ -88,11 +88,15 @@ void SELECT_DRIVE (ide_drive_t *drive) > >>>>> { > >>>>> ide_hwif_t *hwif = drive->hwif; > >>>>> const struct ide_port_ops *port_ops = hwif->port_ops; > >>>>> + ide_task_t task; > >>>>> > >>>>> if (port_ops && port_ops->selectproc) > >>>>> port_ops->selectproc(drive); > >>>>> > >>>>> - hwif->OUTB(drive->select.all, hwif->io_ports.device_addr); > >>>>> + memset(&task, 0, sizeof(task)); > >>>>> + task.tf_flags = IDE_TFLAG_OUT_DEVICE; > >>>>> + > >>>>> + drive->hwif->tf_load(drive, &task); > >>>>> > >>>> This actually doesn't seem like a bright idea to me, considering > >>>> that this gets called when starting every request. How will you look > >>>> at me adding the transport method for writing this register? :-) > >>>> > > > > Please check profiles first -- it might not be worth it. [1] > > > > > >>> Convert SELECT_DRIVE() to use ->tf_load instead of ->OUTB. > >>> > >>> OTOH, adding such a "backdoor" to the taskfile doesn't seem very > >>> consistent... well, I'm not excited about the whole idea conversion to > >>> tf_{load|read}() -- it's not clear what exactly this bought us. > >>> > > > > This was explained some months ago already, so just to recall -- it was > > a part of a bigger work removing duplicated code and allowing abstraction > > of the ATA logic. > > > > Anyway this is not set in a stone so if you have proposal of a better > > approach please come forward with it. > > > > Er... I think that the previous IN()/OUT() methods were better. Note > that we ended up using the local version of them in the dafault > ide_tf_{load}read}() anyway -- as Alan has pointed out it might be worth During ide_tf_{load,read}() addition I was a bit too optimistic about the possibility of the quick io{read,write}* conversion later... > splitting those into I/O and memory space versions... although given > general slowness of the I/O accesses, this is probably not going to win > much speed-wise. Maybe it would be worth to add ->tf_{inb,outb} to struct ide_tp_ops and convert default tp_ops to use them... OTOH we should reinvestigate the io{read,write}*() way first (maybe things have improved there)... > >> We at least could have saved on memset() -- tf_load() method ignores > >> fields other than tf_flags anyway... > >> > > > > Unless it is huge performance win (unlikely) this is not a good idea as it would be a maintainance nightmare. > > > > ->tf_load does only use cmd->tf_flags today but it might change one day > > and nobody will remember to audit all users that they pass a valid cmd... > > > > It's just quite unbearable to see (especially for a long time > assembly coder) how a single register write is turning into *that*. > So, it still seems worth risking... :-) I see your point here. If SELECT_DRIVE() is performance sensitive we may just add another struct ide_tp_ops method for it... Thanks, Bart