Messages in this thread Patch in this message | | | From | Robert Abel <> | Subject | [PATCH 1/2] auxdisplay: charlcd: fix x/y address commands | Date | Wed, 28 Feb 2018 01:05:35 +0100 |
| |
The current version does not parse x/y commands at all. Simplify the x/y command syntax to the one indicated in the comment all along and introduce a parsing function that handles parsing a sequence of one or two subcommands where each subcommand must appear at most once.
Signed-off-by: Robert Abel <rabel@robertabel.eu> --- drivers/auxdisplay/charlcd.c | 109 +++++++++++++++++++++++++++++++++++++------ 1 file changed, 96 insertions(+), 13 deletions(-)
diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index e3b2fd15c5a3..ae078f414539 100644 --- a/drivers/auxdisplay/charlcd.c +++ b/drivers/auxdisplay/charlcd.c @@ -292,6 +292,96 @@ static int charlcd_init_display(struct charlcd *lcd) return 0; } +/** + * parse_xy() - Parse coordinates of a movement command. + * @s: Pointer to null-terminated movement command string. + * @x: Pointer to x position. + * @y: Pointer to y position. + * + * Parses a movement command of the form "([xy][0-9]+){1,2};", + * where each group must begin with a different subcommand. + * + * The positions will only be updated when their respective + * subcommand is encountered and when the whole movement + * command is valid. + * + * The movement command string must contain a ';' at the end. + * + * For instance: + * - ";" fails. + * - "x1;" returns (1, <original y>). + * - "y2x1;" returns (1, 2). + * - "x12y34x56;" fails. + * - "" fails. + * - "x" illegal input. + * - "x;" fails. + * - "x1" illegal input. + * - "xy12;" fails. + * - "x12yy12;" fails. + * - "xx" illegal input. + * + * Return: Returns whether the command is valid. The position arguments are + * only written if the parsing was successful. + */ +static bool parse_xy(const char *s, unsigned long *x, unsigned long *y) +{ + + unsigned long new_x = *x; + unsigned long new_y = *y; + + char xcoord[LCD_ESCAPE_LEN]; + char ycoord[LCD_ESCAPE_LEN]; + const char *split = strpbrk(s + 1, "xy"); + const char *end = strchr(s, ';'); + char *coord0 = xcoord; + char *coord1 = ycoord; + unsigned long *new0 = &new_x; + unsigned long *new1 = &new_y; + + memset(xcoord, 0, sizeof(xcoord)); + memset(ycoord, 0, sizeof(ycoord)); + + /* validate input */ + switch (*s) { + case 'x': + if (split != NULL && *split != 'y') + return false; + break; + case 'y': + /* swap coordinates */ + coord0 = ycoord; + coord1 = xcoord; + new0 = &new_y; + new1 = &new_x; + + if (split != NULL && *split != 'x') + return false; + break; + default: + return false; + } + + /* parse coordinate 0 and 1 */ + if (split == NULL) { + memcpy(coord0, s + 1, end - s - 1); + if (kstrtoul(coord0, 10, new0) < 0) + return false; + } else { + memcpy(coord0, s + 1, split - s - 1); + memcpy(coord1, split + 1, end - split - 1); + if (kstrtoul(coord0, 10, new0) < 0) + return false; + if (kstrtoul(coord1, 10, new1) < 0) + return false; + } + + /* update coordinates on success */ + *x = new_x; + *y = new_y; + return true; + +} + /* * These are the file operation function for user access to /dev/lcd * This function can also be called from inside the kernel, by @@ -473,21 +563,14 @@ static inline int handle_lcd_special_code(struct charlcd *lcd) if (!strchr(esc, ';')) break; - while (*esc) { - if (*esc == 'x') { - esc++; - if (kstrtoul(esc, 10, &priv->addr.x) < 0) - break; - } else if (*esc == 'y') { - esc++; - if (kstrtoul(esc, 10, &priv->addr.y) < 0) - break; - } else { - break; - } + /* If the command is valid, move to the new address */ + if (parse_xy(esc, &priv->addr.x, &priv->addr.y)) { + priv->addr.x = min_t(unsigned long, priv->addr.x, lcd->bwidth - 1); + priv->addr.y %= lcd->height; + charlcd_gotoxy(lcd); } - charlcd_gotoxy(lcd); + /* Regardless of its validity, mark as processed */ processed = 1; break; } -- 2.11.0
| |