Re: i8042 access timings

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Wed, 26 Jan 2005 12:05:47 -0500 (EST), linux-os
<linux-os@analogic.com> wrote:
> On Wed, 26 Jan 2005, Dmitry Torokhov wrote:
> 
> > On Wed, 26 Jan 2005 16:43:07 +0100, Vojtech Pavlik <vojtech@suse.cz> wrote:
> >> On Tue, Jan 25, 2005 at 02:41:14AM -0500, Dmitry Torokhov wrote:
> >>> @@ -213,7 +217,10 @@
> >>>       if (!retval)
> >>>               for (i = 0; i < ((command >> 8) & 0xf); i++) {
> >>>                       if ((retval = i8042_wait_read())) break;
> >>> -                     if (i8042_read_status() & I8042_STR_AUXDATA)
> >>> +                     udelay(I8042_STR_DELAY);
> >>> +                     str = i8042_read_status();
> >> []
> >>> +                     udelay(I8042_DATA_DELAY);
> >>> +                     if (str & I8042_STR_AUXDATA)
> >>>                               param[i] = ~i8042_read_data();
> >>>                       else
> >>>                               param[i] = i8042_read_data();
> >>
> >> We may as well drop the negation. It's a bad way to signal the data came
> >> from the AUX port. Then we don't need the extra status read and can just
> >> proceed to read the data, since IMO we don't need to wait inbetween,
> >> even according to the IBM spec.
> >
> > Do you remember why it has been done to begin with?
> >
> > --
> > Dmitry
> 
> 
> The only time you need any delay at all is after you have send
...

Thank you Richard for this thorough explanation of IO access but I was
actually asking why we wanted to invert AUX data.

-- 
Dmitry