Alan Cox writes:
> On Thu, 24 May 2007 09:45:37 -0400
> David Woodhouse <[email protected]> wrote:
>
> > On Thu, 2007-05-24 at 14:41 +0100, Alan Cox wrote:
> > > Most people copied the x86 behaviour which makes it easy to transplant.
> > > Some are just smoking something (see ioctls.h for sh-64 and weep), others
> > > have slightly odd behaviour for historical compatibility reasons (Sparc)
> >
> > Likewise, I assume the lack of IBSHIFT on PowerPC is because of AIX?
>
> I assume nobody ever got around to it. CIBAUD is in the PowerPC System V
> API supplement for example and is supported by other Power OS's.
The guys that did the original ppc linux port (mainly Gary Thomas and
Cort Dougan, I believe) tended to follow the alpha and x86 linux ports
rather than the System V ABI. There aren't any SysV-based OSes for
PowerPC still extant so it doesn't really matter.
And yes, nobody has got around to implementing CIBAUD/IBSHIFT.
> > Why bother introducing new IBSHIFT stuff when it can be declared
> > obsolete already -- if you want different input and output baud rates,
> > just set BOTHER and have different values c_ispeed and c_ospeed.
>
> BOTHER is for the output speed. BOTHER << IBSHIFT is for the input speed
> if it different to the default (and you need B0 << IBSHIFT to know if an
> input speed is being specifically set in the first place).
>
> CIBAUD and IBSHIFT come from standards documents so it appears to make
> sense at some level to support those standards. As everyone else in the
> Power world supports it I don't see why Linux should be different.
Sure, we can add them. I suggest IBSHIFT = 16 and CIBAUD = 0xff0000
(or 077600000 if we are going to continue the peculiar convention of
using octal for the C* constants).
Paul.
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