linux-kernel - Re: [PATCH 1/3] auxdisplay: charlcd: fix hex literal ranges for graphics command

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Date:   Mon, 26 Feb 2018 00:34:19 +0100
From:   Robert Abel <rabel@...ertabel.eu>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Willy Tarreau <w@....eu>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] auxdisplay: charlcd: fix hex literal ranges for
 graphics command

Hi Andy,

On 15 Feb 2018 11:57, Andy Shevchenko wrote:
> On Thu, Feb 15, 2018 at 1:17 AM, Robert Abel <rabel@...ertabel.eu> wrote:
>> hex_to_bin look fine to me, although personally I'm not a big fan of its
>> use of tolower.
> 
> Let's duplicate then over and over?

I was speaking more generally about performance here. There is a reason
for kstrtox.c:57
(https://elixir.bootlin.com/linux/v4.14.7/source/lib/kstrtox.c#L57)
> unsigned int lc = c | 0x20; /* don't tolower() this line */

> Can you point to the documentation where user can easily (w/o reading
> the code) get how it suppose to be?

Unfortunately not. I read the code myself to know how it is supposed to
work. That's definitely a gap in documentation.

> On Thu, Feb 15, 2018 at 1:17 AM, Robert Abel <rabel@...ertabel.eu> wrote:
>> I noticed the only part of the code that does make use of library
>> functions, parsing x and y coordinates using kstrtoul, is broken.
>> Apparently it used to use simple_strtoul, which worked and then got
>> replaced.
> By which commit?

129957069e6af42a6e021d90679c56662c95f7e1
(https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=129957069e6af42a6e021d90679c56662c95f7e1)

I'll try to answer to this email with relevant patches for charlcd.c.

Regards,

Robert