linux-kernel - Re: [PATCH 3/3] tty: support CIBAUD without BOTHER

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Message-ID: <20180716104411.GA11023@kroah.com>
Date:   Mon, 16 Jul 2018 12:44:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Jiri Slaby <jslaby@...e.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] tty: support CIBAUD without BOTHER

On Mon, Jul 16, 2018 at 12:18:24PM +0200, Johan Hovold wrote:
> On Mon, Jul 16, 2018 at 12:00:28PM +0200, Greg Kroah-Hartman wrote:
> > On Sun, Jul 15, 2018 at 03:39:35PM +0200, Johan Hovold wrote:
> > > Since commit edc6afc54968 ("[PATCH] tty: switch to ktermios and new
> > > framework") arbitrary baud rates can be requested using BOTHER and input
> > > rates can be requested using the termios CIBAUD bits (CBAUD shifted
> > > IBSHIFT bits).
> > > 
> > > This functionality has been conditionally compiled depending on whether
> > > an architecture defines BOTHER and IBSHIFT respectively, but would in
> > > fact fail to compile unless both symbols were defined due to cross
> > > dependencies.
> > > 
> > > Relax the IBSHIFT => BOTHER dependency so that an architecture could
> > > theoretically support CIBAUD without the Linux-specific BOTHER, while
> > > hopefully making the current conditional-compilation directives a bit
> > > less confusing.
> > > 
> > > Note that the long-term goal is still to have all architectures support
> > > both features, so an alternative could just be to have the lot depend on
> > > BOTHER.
> > 
> > I thought we had all arches converted to use BOTHER already, what ones
> > are not yet done?  It's hard to unwind the asm-generic use of termbits.h
> > to obviously see which ones are not doing this yet, any ideas?
> 
> It looks like alpha does not yet define BOTHER at least.

Someday we will get to delete alpha and many people will be happy :)

> > Oh, and thanks for fixing this all up, odd that no one has noticed it
> > before.
> 
> Probably due to there being no in-tree drivers that support separate
> input rates. And with no glibc support for BOTHER (still), it's somewhat
> less likely that people will trigger the bug that could end up setting
> CIBAUD for them.

Ugh, I thought glibc got support for it, I guess everyone just
hand-codes it in their applications for now.  Sad.

Anyway, thanks for the patches, all now applied.

greg k-h