linux-kernel - Re: [PATCH 3/4] auxdisplay: charlcd: fix x/y address commands

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Date:   Wed, 28 Feb 2018 00:29:38 +0100
From:   Robert Abel <rabel@...ertabel.eu>
To:     Willy Tarreau <w@....eu>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH 3/4] auxdisplay: charlcd: fix x/y address commands

Hi Willy,

On 27 Feb 2018 06:19, Willy Tarreau wrote:
> Well actually I don't see a problem there at all. The principle is simply
> to accept any sequence assigning x or y or both. If you write x4y2x6, it
> simply means that you changed your mind regarding x and that the last
> value (6) is the one you want. Just as if you wrote "^[[Lx4;^[[y2;^[[x6;".
> The while loop doesn't even try to do anything clever, it simply parses
> everything matching x and y followed by digits. I think the only reason
> for having both x and y processed in the same loop was to call
> charlcd_gotoxy() only once for both axes.

I didn't say it is a problem. It is however an edge case that incurs a
lot of code for little to no functionality.
I'd much prefer if we broke backwards compatibility here and actually
only parse the format that is indicated in the comment:

>         case 'x':       /* gotoxy : LxXXX[yYYY]; */
>         case 'y':       /* gotoxy : LyYYY[xXXX]; */
>  

Exactly one x command followed exactly by zero or one y command or
vice-versa.

If somebody changes their mind during the escape sequence, they can just
issue a new one instead of appending to the current one.

I'll post an example patch.

Regards,

Robert