linux-kernel - Re: [PATCH 8/8] vt: process the full-width ASCII fallback range programmatically

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Message-ID: <ss849930-nr48-q998-oo41-3qs64or91670@syhkavp.arg>
Date: Wed, 7 May 2025 10:04:16 -0400 (EDT)
From: Nicolas Pitre <nico@...xnic.net>
To: Jiri Slaby <jirislaby@...nel.org>
cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] vt: process the full-width ASCII fallback range
 programmatically

On Tue, 6 May 2025, Jiri Slaby wrote:

> On 05. 05. 25, 18:55, Nicolas Pitre wrote:
> > From: Nicolas Pitre <npitre@...libre.com>
> > 
> > This saves about 258 bytes of text.
> 
> You mean .rodata, actually?

I used the `size`command which lumps .text and .rodata together. In 
reality .rodata goes down and .text goes up a little, and the end result 
is the combined text size.

> > --- a/drivers/tty/vt/ucs.c
> > +++ b/drivers/tty/vt/ucs.c
> > @@ -222,5 +222,13 @@ u32 ucs_get_fallback(u32 cp)
> >    if (single)
> >     return ucs_fallback_singles_subs[single - ucs_fallback_singles];
> >   +	/*
> > +	 * Full-width to ASCII mapping (covering all printable ASCII 33-126)
> > +	 * 0xFF01 (！) to 0xFF5E (～) -> ASCII 33 (!) to 126 (~)
> > +	 * We process them programmatically to reduce the table size.
> > +	 */
> > +	if (cp >= 0xFF01 && cp <= 0xFF5E)
> > +		return cp - 0xFF01 + 33;
> 
> So do really »+ '!'« instead of »+ 33«.

Uh... why? Having both as numerical value is more meaningful and clearer 
here IMHO.


Nicolas