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SubjectRe: Russell King forks ARM Linux.
On Wed, Sep 27, 2000 at 02:30:13PM -0700, H. Peter Anvin wrote:
>
> For what it's worth, the SA1100 serial driver has been registered with
> me on the Low-Density Serial Ports major (204) as /dev/ttySA0-2 (minor
> 5-7).
>
> Russ is 100% correct that different drivers shouldn't use the
> same device numbers, unless they are:
>
> a) mutually exclusive,
> b) interface compatible, *AND*
> c) handle all arbitration necessary.
>
> If (a), (b) and (c) are all satisfied, it is often justified to share
> device numbers and device nodes.

I jumped into this discussion on linux-arm-kernel before realizing
it had wandered here.

I don't see the major 204 allocation in devices.txt, so I'm not sure if
this has already been covered, but it would be nice to have an allocation
for "on-chip UARTs" in system-on-chip type configurations. I recently
worked on a port to the Cirrus Logic EP7211, which is an ARM-based
system-on-chip (CPU, UARTs, LCD controller, DRAM controller, etc.)
It seems hoggish to ask for an allocation for such a non-general-purpose
piece of hardware.

If we had (say) 4 or 8 on-chip UART device numbers for regular serial,
plus a corresponding 4 or 8 for serial IR using the same UARTs, that
would cover things nicely (EP7211 has only 2 UARTs but I figure it'll be
good to leave some room). And on-chip UARTs are by definition mutually
exclusive (unless you start talking about sharing /dev via NFS between
heterogeneous embedded systems).

miket

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