Bartlomiej Zolnierkiewicz wrote:
There should be no functional changes caused by this patch.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
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)...
Yes, let's not be hasty here...
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...
Or we may finally teach selectproc() to also do that, turning it into
analog of libata's dev_select() method.
Thanks,
Bart
MBR, Sergei
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