Re: [PATCH] $ARCH: Enable arbitary speed tty ioctls and split input/output speed

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Thu, 24 May 2007 09:08:55 -0400
David Woodhouse <dwmw2@infradead.org> wrote:

> Is my mailbox (or brain) failing me, or did you just send out these
> patches for every architecture _except_ PowerPC? :)

PowerPC is one of the main ones I've not touched because it needs work
itself to sort out the IBSHIFT value and bit allocations, also because
its one of several dependant upon the asm-generic stuff (which also means
your patch won't work)

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)

> Presumably this is because of the mess in tty_termios_encode_baud_rate
> when we fix its bogus assumptions about IBSHIFT always being defined?

It's not a bogus assumption. The current code supports

	- The old way
	- BOTHER and IBSHIFT

When PPC wants to do arbitary baud rate it needs to resolve both of the
definitions together. IBSHIFT is simply the shift you apply to the baud
bits to get the input baud bits.

Alan