Hello.
Sergei Shtylyov wrote:
other devices on the bus). By overriding the data transfer function
I can
arbitrate access to the bus and switch the bus timings based on the
peripheral being accessed. This cannot be done be a generic data
transfer
function.
I disagree with your approach of overriding the libata methods at the
board level, so I suggest to write a new driver. This is too
complicated
stuff for poor old pata_platform. :-)
My custom function to date looks like:
unsigned int ata_enet_data_xfer(struct ata_device *dev, unsigned char
*buf,
unsigned int buflen, int rw)
{
struct ata_port *ap = dev->link->ap;
void __iomem *data_addr = ap->ioaddr.data_addr;
set_gp_bus_slow();
/* Transfer bytes */
if (rw == READ)
ioread8_rep(data_addr, buf, buflen);
else
iowrite8_rep(data_addr, buf, buflen);
set_gp_bus_fast();
return buflen;
}
set_gp_bus_slow() and set_gp_bus_fast() (at the moment) simply set a few
config registers to set the GP bus timing (no arbitration yet, but these
BTW, do you know that there are different ATA PIO transfer modes with
different timings?
functions will also handle that using a mutex). I don't see the point in
re-writing the entire PATA Platform driver when the existing driver
appears
to be perfectly capable with a very minor extension hook.
As I said, we *can't* implement the driver methods at the board
level. Especially if they involve messing with timings -- that's the
point where the ATA driver stops being generic, like pata_platform,
and there arises a need for the dedicated driver. Also, your patch
would bring in disparity with the ide-platfrom driver (which should be
interchangeable with pata_platfrom). For me, the need of a separate
driver is clear now, so I'll remain opposed to your patch. Of course,
the maintainer (Jeff Garzik) will decide but if I could veto this
patch I would.
At the very least, you should remove 'struct ata_device *' parameter
from your hook, so that it could be called from the IDE driver also.
Without this change, the patch will remain totally unacceptable.
Graeme
Regards,
WBR, Sergei
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