Re: [PATCH stable v2 1/2] arch/alpha, termios: implement BOTHER, IBSHIFT and termios2

[Johan Hovold <johan@kernel.org>]

On Sun, Oct 07, 2018 at 09:06:19PM -0700, H. Peter Anvin wrote:
> From: "H. Peter Anvin (Intel)" <hpa@zytor.com>
> 
> Alpha has had c_ispeed and c_ospeed, but still set speeds in c_cflags
> using arbitrary flags. Because BOTHER is not defined, the general
> Linux code doesn't allow setting arbitrary baud rates, and because
> CBAUDEX == 0, we can have an array overrun of the baud_rate[] table in
> drivers/tty/tty_baudrate.c if (c_cflags & CBAUD) == 037.
> 
> Resolve both problems by #defining BOTHER to 037 on Alpha.
> 
> However, userspace still needs to know if setting BOTHER is actually
> safe given legacy kernels (does anyone actually care about that on
> Alpha anymore?), so enable the TCGETS2/TCSETS*2 ioctls on Alpha, even
> though they use the same structure. Define struct termios2 just for
> compatibility; it is the exact same structure as struct termios. In a
> future patchset, this will be cleaned up so the uapi headers are
> usable from libc.

Is this really needed? By defining BOTHER (and IBSHIFT which you forgot
to mention here) you are enabling arbitrary rates also through TCSETS on
alpha, right?

Johan