[PATCH v5.2 07/12] termios: change the generic cfsetspeed() to support arbitrary speeds

[Adhemerval Zanella Netto]

On 27/05/25 19:08, H. Peter Anvin wrote:
> The generic implementaion of cfsetspeed() had an internal table of

s/implementaion/implementation

> permitted baud rates, which was enforced even on an implementation
> supporting arbitrary baud rates. This was to be able to *also* accept
> numeric constants as well as Bxxx values.
> 
> This fundamentally makes no sense; not only does it go against the
> documented behavior of cfsetspeed() which is to take the same input
> as cfset[io]speed(), but it means cfsetspeed() is broken with regard
> to a platform supporting arbitrary speeds.
> 
> With Linux converted to arbitrary baud rates, the only remaining case
> of non-arbitrary baud rates appears to be Hurd with USE_OLD_TTY, which
> one can presume being a legacy case that few if any people care about,
> and so simply strip out this code and make cfsetspeed() rely on
> cfsetospeed() to validate acceptable speed constants.
> 
> If a new platform is introduced which does not have arbitrary baud
> rate support, using non-baud rate Bxxx constants (highly not
> recommended; should be abstracted at the glibc level) but such
> aliasing is desired, it should be supported by cfset[io]speed() as
> well, and belongs in the platform-specific code.
> 
> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  termios/cfsetspeed.c | 138 ++-----------------------------------------
>  1 file changed, 5 insertions(+), 133 deletions(-)
> 
> diff --git a/termios/cfsetspeed.c b/termios/cfsetspeed.c
> index 053e3945ea10..257c6387aaa0 100644
> --- a/termios/cfsetspeed.c
> +++ b/termios/cfsetspeed.c
> @@ -19,143 +19,15 @@
>  #include <errno.h>
>  #include <stddef.h>
>  
> -struct speed_struct
> -{
> -  speed_t value;
> -  speed_t internal;
> -};
> -
> -static const struct speed_struct speeds[] =
> -  {
> -#ifdef B0
> -    { 0, B0 },
> -#endif
> -#ifdef B50
> -    { 50, B50 },
> -#endif
> -#ifdef B75
> -    { 75, B75 },
> -#endif
> -#ifdef B110
> -    { 110, B110 },
> -#endif
> -#ifdef B134
> -    { 134, B134 },
> -#endif
> -#ifdef B150
> -    { 150, B150 },
> -#endif
> -#ifdef B200
> -    { 200, B200 },
> -#endif
> -#ifdef B300
> -    { 300, B300 },
> -#endif
> -#ifdef B600
> -    { 600, B600 },
> -#endif
> -#ifdef B1200
> -    { 1200, B1200 },
> -#endif
> -#ifdef B1200
> -    { 1200, B1200 },
> -#endif
> -#ifdef B1800
> -    { 1800, B1800 },
> -#endif
> -#ifdef B2400
> -    { 2400, B2400 },
> -#endif
> -#ifdef B4800
> -    { 4800, B4800 },
> -#endif
> -#ifdef B9600
> -    { 9600, B9600 },
> -#endif
> -#ifdef B19200
> -    { 19200, B19200 },
> -#endif
> -#ifdef B38400
> -    { 38400, B38400 },
> -#endif
> -#ifdef B57600
> -    { 57600, B57600 },
> -#endif
> -#ifdef B76800
> -    { 76800, B76800 },
> -#endif
> -#ifdef B115200
> -    { 115200, B115200 },
> -#endif
> -#ifdef B153600
> -    { 153600, B153600 },
> -#endif
> -#ifdef B230400
> -    { 230400, B230400 },
> -#endif
> -#ifdef B307200
> -    { 307200, B307200 },
> -#endif
> -#ifdef B460800
> -    { 460800, B460800 },
> -#endif
> -#ifdef B500000
> -    { 500000, B500000 },
> -#endif
> -#ifdef B576000
> -    { 576000, B576000 },
> -#endif
> -#ifdef B921600
> -    { 921600, B921600 },
> -#endif
> -#ifdef B1000000
> -    { 1000000, B1000000 },
> -#endif
> -#ifdef B1152000
> -    { 1152000, B1152000 },
> -#endif
> -#ifdef B1500000
> -    { 1500000, B1500000 },
> -#endif
> -#ifdef B2000000
> -    { 2000000, B2000000 },
> -#endif
> -#ifdef B2500000
> -    { 2500000, B2500000 },
> -#endif
> -#ifdef B3000000
> -    { 3000000, B3000000 },
> -#endif
> -#ifdef B3500000
> -    { 3500000, B3500000 },
> -#endif
> -#ifdef B4000000
> -    { 4000000, B4000000 },
> -#endif
> -  };
> -
> -
>  /* Set both the input and output baud rates stored in *TERMIOS_P to SPEED.  */
>  int
>  cfsetspeed (struct termios *termios_p, speed_t speed)
>  {
> -  size_t cnt;
> -
> -  for (cnt = 0; cnt < sizeof (speeds) / sizeof (speeds[0]); ++cnt)
> -    if (speed == speeds[cnt].internal)
> -      {
> -	cfsetispeed (termios_p, speed);
> -	cfsetospeed (termios_p, speed);
> -	return 0;
> -      }
> -    else if (speed == speeds[cnt].value)
> -      {
> -	cfsetispeed (termios_p, speeds[cnt].internal);
> -	cfsetospeed (termios_p, speeds[cnt].internal);
> -	return 0;
> -      }
> +  int rv;
>  
> -  __set_errno (EINVAL);
> +  rv = cfsetospeed (termios_p, speed);
> +  if (rv)
> +    return rv;
>  
> -  return -1;
> +  return cfsetispeed (termios_p, speed);
>  }

Ok.