Re: [PATCH] Generic platform device IDE driver

[Jeff Garzik <jgarzik@pobox.com>]

Paul Mundt wrote:
> On Fri, Oct 13, 2006 at 08:52:19AM +0100, Russell King wrote:
> > On Thu, Oct 12, 2006 at 03:13:48PM +0900, Paul Mundt wrote:
> > > Yes, that's one thing I was thinking of as well.. Here's a patch that
> > > makes an attempt at that, can you give it a try and see if it works for
> > > you? This applies on top of the earlier patch. None of the ARM, SH, or
> > > H8300 cases need to do the remapping at least.
> > It's likely that ARM will switch over to using the MMIO resources if
> > this patch makes it in.  There's certain ARM platforms which would
> > benefit from this change (since inb() and friends are more complex
> > than they necessarily need to be.)
> >
> > However, one issue needs to be solved before we could do that - how do
> > we handle the case where the IDE registers are on a 4 byte spacing
> > interval instead of the usual 1 byte?
> We could solve this in the driver, but it sounds like this is something
> that libata should have some visibility of directly.
>
> > I notice that this driver is calling ata_std_ports() which handles
> > the standard setup.  Maybe that needs to become a little more inteligent?
> If we go this route, I suppose the easiest option will be simply to have
> a private structure with a few function pointers for these sorts of
> things, or we can simply have an element for the spacing interval if you
> don't forsee needing to change the ioaddrs in any fashion beyond the
> register spacing.. Which approach would you be more comfortable with?
> Are there any other items that you're concerned with in the current
> driver?


Here's the decision matrix for libata:  Will the hardware use the 
standard taskfile push/pull functions like ata_tf_load(), ata_tf_read(), 
ata_exec_command(), etc.?  If yes, simply replace ata_std_ports() call 
with a call to your own function, written similarly to 
pdc_ata_setup_port() in sata_promise.c.

If the hardware requires non-standard I/O accessors, or the register 
sizes themselves changed, then you must implement your own taskfile I/O 
functions, similar to k2_sata_tf_load(), k2_sata_tf_read(), and 
k2_bmdma_setup_mmio() in sata_svw.c.  For this case, data in struct 
ata_ioports is largely up to you to manage, or ignore.

If there are special command setup or teardown operations, there are 
other standard hooks to override as well.

	Jeff


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/