Messages in this thread | | | Date | Tue, 17 Feb 2009 04:04:11 +0300 | From | Sergei Shtylyov <> | Subject | Re: [PATCH 13/18] ide: use ->tf_load in SELECT_DRIVE() |
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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 <bzolnier@gmail.com> >>>>> 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
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