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

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Date:   Mon, 26 Feb 2018 17:54:59 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Robert Abel <rabel@...ertabel.eu>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Willy Tarreau <w@....eu>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH 3/4] auxdisplay: charlcd: fix x/y address commands

On Mon, Feb 26, 2018 at 12:44 PM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Mon, Feb 26, 2018 at 1:54 AM, Robert Abel <rabel@...ertabel.eu> wrote:
>> NUL-terminate each individual number to be parsed.
>> To do this, the next command character and a pointer to its argument
>> are found and stored. The command character is then overwritten by NUL
>> before kstr* functions are called on the buffer.
>
> Can we avoid yoda style of programming?
>
>>         case 'x':       /* gotoxy : LxXXX[yYYY]; */
>> +       case 'y': {     /* gotoxy : LyYYY[xXXX]; */
>> +
>> +               char* nxt_esc;
>> +               char  nxt_cmd;
>> +               char  cmd;
>> +               struct charlcd_priv_addr tmp_addr;
>> +
>>                 if (!strchr(esc, ';'))
>>                         break;
>>
>> +               /* sequence is processed whether legal or illegal */
>> +               processed = 1;
>> +
>> +               /* copy current address to temporary buffer */
>> +               tmp_addr = priv->addr;
>> +
>> +               nxt_cmd = *esc++;
>> +               nxt_esc = esc;
>> +
>> +               while ('\0' != *esc) {
>> +
>> +                       cmd = nxt_cmd;
>> +                       esc = nxt_esc;
>> +                       nxt_esc = strpbrk(esc, "xy;");
>> +                       if (NULL != nxt_esc) {
>> +                               nxt_cmd = *nxt_esc;
>> +                               /* terminate current sequence with NUL */
>> +                               *nxt_esc++ = '\0';
>> +                       }
>> +
>> +                       if ('x' == cmd) {
>> +                               if (kstrtoul(esc, 10, &tmp_addr.x) < 0)
>>                                         break;
>
>> +                       } else if ('y' == cmd) {
>> +                               if (kstrtoul(esc, 10, &tmp_addr.y) < 0)
>>                                         break;
>
> Perhaps instead of dancing around kstrtox() better to switch to
> simple_strtoul() ?

It seems deprecated:

/* Obsolete, do not use.  Use kstrto<foo> instead */
extern unsigned long simple_strtoul(const char *,char **,unsigned int);

>
>>                         } else {
>> +                               /* break on unknown command or ';' */
>>                                 break;
>>                         }
>> +
>>                 }
>>
>> +               /* unknown commands in sequence will be followed by at least ';' */
>> +               if ('\0' != *esc)
>> +                       break;
>> +
>> +               /* clamp new x/y coordinates */
>> +               if (tmp_addr.x >= lcd->width)
>> +                       tmp_addr.x = lcd->width - 1;
>> +               tmp_addr.y %= lcd->height;
>> +
>> +               priv->addr = tmp_addr;
>>                 charlcd_gotoxy(lcd);
>>                 break;
>
>>         }
>> +       }
>
> Same indentation level or my mailer hides this from me?

It is the same, but it is also how the other 'case's do it -- which in
this case looks just wrong since it is the last one of the switch. I
am not sure what is the preferred way of doing these kind of blocks,
coding-style.rst does not seem to give an example for this case.

Cheers,
Miguel

>
> --
> With Best Regards,
> Andy Shevchenko