From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754762AbZBQBE1 (ORCPT ); Mon, 16 Feb 2009 20:04:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751319AbZBQBES (ORCPT ); Mon, 16 Feb 2009 20:04:18 -0500 Received: from h155.mvista.com ([63.81.120.155]:4539 "EHLO imap.sh.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751170AbZBQBER (ORCPT ); Mon, 16 Feb 2009 20:04:17 -0500 Message-ID: <499A0D0B.7070007@ru.mvista.com> Date: Tue, 17 Feb 2009 04:04:11 +0300 From: Sergei Shtylyov User-Agent: Thunderbird 2.0.0.19 (Windows/20081209) MIME-Version: 1.0 To: Bartlomiej Zolnierkiewicz Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/18] ide: use ->tf_load in SELECT_DRIVE() References: <20080620213323.13202.71450.sendpatchset@localhost.localdomain> <4998AE87.3020502@ru.mvista.com> <49995300.7030102@ru.mvista.com> <200902162251.49271.bzolnier@gmail.com> In-Reply-To: <200902162251.49271.bzolnier@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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. >> 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... :-) > Thanks, > Bart > MBR, Sergei