Re: git: ba48d52ca6c8 - main - vt: Fix frequency calcuation for bell

Thank you Warner for all the legwork on tracking this down and
getting a proper bell tone working on FreeBSD-Current.  I do not
see any MFC plans for this, can you please consider merging this
to all supported releases?

Oh and RELNOTES: YES?

Thanks,
Rod

> The branch main has been updated by imp:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=ba48d52ca6c867559156dd916631f9ac47abe80f
> 
> commit ba48d52ca6c867559156dd916631f9ac47abe80f
> Author:     Warner Losh <imp@FreeBSD.org>
> AuthorDate: 2021-11-03 21:55:55 +0000
> Commit:     Warner Losh <imp@FreeBSD.org>
> CommitDate: 2021-11-03 22:03:51 +0000
> 
>     vt: Fix frequency calcuation for bell
>     
>     386BSD provided a MD function sysbeep. This took two arguments (pitch
>     and period). Pitch was jammed into the PIT's divisor directly (which
>     means the argument was expected to sound a tone at '1193182 / pitch'
>     Hz). FreeBSD inherited this interface.
>     
>     In commit e46598588587 (svn 177642, Mar 26 2008), phk changed this
>     function to take a tone to sound in hz. He converted all in-tree
>     instances of 1193182 / hz to just hz (and kept the few misguided folks
>     that passed hz directly unchanged -- this was part of what motivated the
>     change). He converted the places where we pre-computed the 8254 divisor
>     from being pitch to 1193182 / pitch (since that converts the divisor to
>     the frequency and the interfaces that were exposed to userland exposed
>     it in these units in places, continuing the tradition inherited from SCO
>     System V/386 Unix in spots).
>     
>     In 2009, Ed Shouten was contracted by the FreeBSD Foundation to write /
>     finish newcons. This work was done in perforce and was imported into
>     subversion in user/ed/newcons in revision 199072
>     (https://svnweb.freebsd.org/base?view=revision&revision=199072) which
>     was later imported into FreeBSD by ray@ (Aleksandr Rybalko).
>     
>     From that earliest import into svn import to this date, we ring the bell
>     with:
>           sysbeep(1193182 / VT_BELLPITCH, VT_BELLDURATION);
>     where VT_BELLPITCH was defined to be 800. This results in a bell
>     frequency of 1491Hz, more or less today. This is similar to the
>     frequency that syscons and pcvt used (1493Hz and 1500Hz respectively).
>     This in turn was inherited from 386BSD, it seems, which used the hard
>     coded value 0x31b which is 795 -> 1500Hz.
>     
>     This '800' was intended to be the bell tone (eg 800Hz) and this
>     interface was one that wasn't converted. The most common terminal prior
>     to the rise of PCs was the VT100, which had an approximately 800Hz
>     bell. Ed Shouten has confirmed that the original intent was 800Hz and
>     changing this was overlooked after the change to -current was made.
>     This restors that original intent and makes the bell less obnoxious in
>     the process.
>     
>     Reviewed by:            des, adrian
>     Differential Revision:  https://reviews.freebsd.org/D32594
>     Sponsored by:           Netflix
> ---
>  sys/dev/vt/vt_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sys/dev/vt/vt_core.c b/sys/dev/vt/vt_core.c
> index 38efd1e5501c..06f5827078ca 100644
> --- a/sys/dev/vt/vt_core.c
> +++ b/sys/dev/vt/vt_core.c
> @@ -121,7 +121,7 @@ const struct terminal_class vt_termclass = {
>  
>  /* Bell pitch/duration. */
>  #define	VT_BELLDURATION	(SBT_1S / 20)
> -#define	VT_BELLPITCH	(1193182 / 800) /* Approx 1491Hz */
> +#define	VT_BELLPITCH	800
>  
>  #define	VT_UNIT(vw)	((vw)->vw_device->vd_unit * VT_MAXWINDOWS + \
>  			(vw)->vw_number)
> 

-- 
Rod Grimes                                                 rgrimes@freebsd.org