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

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Message-ID: <50a2fd51-8bdb-d2b7-c2b3-7df638fdedde@robertabel.eu>
Date:   Mon, 26 Feb 2018 23:43:36 +0100
From:   Robert Abel <rabel@...ertabel.eu>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Willy Tarreau <w@....eu>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH 3/4] auxdisplay: charlcd: fix x/y address commands

On 26 Feb 2018 17:49, Miguel Ojeda wrote:
> On a general note, the code seems a bit convoluted for what it does,
> specially without the comment written in the commit message :-) Isn't
> it simpler to use a tiny array in the stack and put the numbers to be
> converted instead of modifying the input sequence and dancing with
> pointers?

That's what I felt at first, too. If we can drop the backwards
compatibility of repeated xy commands, the whole affair gets much
easier, but will unfortunately break existing use.

Ex. ^[[Lx004y002x006; --> x6y2, because repeats of x would just
overwrite earlier values. That's what the while loop allowed in the
first place.

I suspect the while loop to parse was just a clever way of parsing y
followed by x and x followed by y using the same code and the
overwriting behavior is actually an unaccounted-for side-effect.

Regards,

Robert