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SubjectRe: [PATCH 3/4] auxdisplay: charlcd: fix x/y address commands
On Mon, Feb 26, 2018 at 12:54 AM, Robert Abel <rabel@robertabel.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.

It would be useful to have this description in the code itself as a comment.

>
> Signed-off-by: Robert Abel <rabel@robertabel.eu>
> ---
> drivers/auxdisplay/charlcd.c | 53 ++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 44 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
> index a3d364e6c666..24cabe88c7f0 100644
> --- a/drivers/auxdisplay/charlcd.c
> +++ b/drivers/auxdisplay/charlcd.c
> @@ -471,28 +471,63 @@ static inline int handle_lcd_special_code(struct charlcd *lcd)
> break;
> }
> case 'x': /* gotoxy : LxXXX[yYYY]; */
> - case 'y': /* gotoxy : LyYYY[xXXX]; */
> + case 'y': { /* gotoxy : LyYYY[xXXX]; */
> +

Extra empty line.

> + char* nxt_esc;
> + char nxt_cmd;

I think skipping the "e" in the names do not buy us much :)

> + char cmd;
> + struct charlcd_priv_addr tmp_addr;
> +
> if (!strchr(esc, ';'))
> break;
>
> - while (*esc) {
> - if (*esc == 'x') {
> - esc++;
> - if (kstrtoul(esc, 10, &priv->addr.x) < 0)
> + /* 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) {

Please do not change the style of the code w.r.t to the rest of the
file, which writes tests with the non-lvalue on the right-hand side
and do not compare against '\0'. Same for the rest.

> +

Extra empty line.

> + 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 (*esc == 'y') {
> - esc++;
> - if (kstrtoul(esc, 10, &priv->addr.y) < 0)
> + } else if ('y' == cmd) {
> + if (kstrtoul(esc, 10, &tmp_addr.y) < 0)
> break;
> } else {
> + /* break on unknown command or ';' */
> break;
> }

{ } not needed (your patch doesn't touch this -- just pointing it out).

> +
> }
>
> + /* 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.x = min(tmp_addr.x, lcd->width - 1);

> + tmp_addr.y %= lcd->height;
> +
> + priv->addr = tmp_addr;
> charlcd_gotoxy(lcd);
> - processed = 1;
> break;
> }
> + }

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?

Thanks for the patch!

Cheers,
Miguel

>
> /* TODO: This indent party here got ugly, clean it! */
> /* Check whether one flag was changed */
> --
> 2.11.0
>

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