Re: [PATCH 13/18] ide: use ->tf_load in SELECT_DRIVE()

[Sergei Shtylyov]

Hello, I 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...

   What I certainly don't like is how tf_load/read() handle LBA48: there's 
much of the code duplication going on. I'll think what can be done about it 
but it may not be easy to tackle... it looks like 'struct ide_taskfile' needs 
to be reorganized to include 2 6-byte sub-structures.

> > Thanks,
> > Bart

MBR, Sergei

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