On Wed, 4 Nov 1998 10:30:37 +0100 
 Ignatios Souvatzis <ignatios@theory.cs.uni-bonn.de> wrote:

 > Yes, but ports as the Amiga that need variable strides in bus_space anyway
 > will get the double overhead.

Yes, fine...

But the issue is whether or not the stride is a device thing or a bus
thing.

Let's say for example that you have a Cyberdyne Frobnitz workstation.  On
the mainboard is an IDE controller and a 16550 serial port.  The registers
on these devices are spaced mod 4... 1 byte, followed by 3 bytes of gap,
etc.  On this system, it is clearly a stride imposed by the bus they're
attached to.

Now, let's say you have the newer 7000 model ... On this system the
serial port registers are linear (no gap), but the IDE registers are
spaced mod 16.  On this system, it's an issue of how the individual
chips are wired up, i.e. the stride is per-device.

In the first example, it's appropriate to use stride in the bus space
tag.  In the second example, it's appropriate to add register map
support in the driver.

Jason R. Thorpe                                       thorpej@nas.nasa.gov
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