drm/modes: Rewrite the command line parser

Rewrite the command line parser in order to get away from the state machine
parsing the video mode lines.

Hopefully, this will allow to extend it more easily to support named modes
and / or properties set directly on the command line.
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/e32cd4009153b184103554009135c7bf7c9975d7.1560783090.git-series.maxime.ripard@bootlin.com

drivers/gpu/drm/drm_modes.c

@@ -30,6 +30,7 @@
  * authorization from the copyright holder(s) and author(s).
  */
 
+#include <linux/ctype.h>
 #include <linux/list.h>
 #include <linux/list_sort.h>
 #include <linux/export.h>
@@ -1408,6 +1409,151 @@ void drm_connector_list_update(struct drm_connector *connector)
 }
 EXPORT_SYMBOL(drm_connector_list_update);
 
+static int drm_mode_parse_cmdline_bpp(const char *str, char **end_ptr,
+				      struct drm_cmdline_mode *mode)
+{
+	unsigned int bpp;
+
+	if (str[0] != '-')
+		return -EINVAL;
+
+	str++;
+	bpp = simple_strtol(str, end_ptr, 10);
+	if (*end_ptr == str)
+		return -EINVAL;
+
+	mode->bpp = bpp;
+	mode->bpp_specified = true;
+
+	return 0;
+}
+
+static int drm_mode_parse_cmdline_refresh(const char *str, char **end_ptr,
+					  struct drm_cmdline_mode *mode)
+{
+	unsigned int refresh;
+
+	if (str[0] != '@')
+		return -EINVAL;
+
+	str++;
+	refresh = simple_strtol(str, end_ptr, 10);
+	if (*end_ptr == str)
+		return -EINVAL;
+
+	mode->refresh = refresh;
+	mode->refresh_specified = true;
+
+	return 0;
+}
+
+static int drm_mode_parse_cmdline_extra(const char *str, int length,
+					struct drm_connector *connector,
+					struct drm_cmdline_mode *mode)
+{
+	int i;
+
+	for (i = 0; i < length; i++) {
+		switch (str[i]) {
+		case 'i':
+			mode->interlace = true;
+			break;
+		case 'm':
+			mode->margins = true;
+			break;
+		case 'D':
+			if (mode->force != DRM_FORCE_UNSPECIFIED)
+				return -EINVAL;
+
+			if ((connector->connector_type != DRM_MODE_CONNECTOR_DVII) &&
+			    (connector->connector_type != DRM_MODE_CONNECTOR_HDMIB))
+				mode->force = DRM_FORCE_ON;
+			else
+				mode->force = DRM_FORCE_ON_DIGITAL;
+			break;
+		case 'd':
+			if (mode->force != DRM_FORCE_UNSPECIFIED)
+				return -EINVAL;
+
+			mode->force = DRM_FORCE_OFF;
+			break;
+		case 'e':
+			if (mode->force != DRM_FORCE_UNSPECIFIED)
+				return -EINVAL;
+
+			mode->force = DRM_FORCE_ON;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int drm_mode_parse_cmdline_res_mode(const char *str, unsigned int length,
+					   bool extras,
+					   struct drm_connector *connector,
+					   struct drm_cmdline_mode *mode)
+{
+	const char *str_start = str;
+	bool rb = false, cvt = false;
+	int xres = 0, yres = 0;
+	int remaining, i;
+	char *end_ptr;
+
+	xres = simple_strtol(str, &end_ptr, 10);
+	if (end_ptr == str)
+		return -EINVAL;
+
+	if (end_ptr[0] != 'x')
+		return -EINVAL;
+	end_ptr++;
+
+	str = end_ptr;
+	yres = simple_strtol(str, &end_ptr, 10);
+	if (end_ptr == str)
+		return -EINVAL;
+
+	remaining = length - (end_ptr - str_start);
+	if (remaining < 0)
+		return -EINVAL;
+
+	for (i = 0; i < remaining; i++) {
+		switch (end_ptr[i]) {
+		case 'M':
+			cvt = true;
+			break;
+		case 'R':
+			rb = true;
+			break;
+		default:
+			/*
+			 * Try to pass that to our extras parsing
+			 * function to handle the case where the
+			 * extras are directly after the resolution
+			 */
+			if (extras) {
+				int ret = drm_mode_parse_cmdline_extra(end_ptr + i,
+								       1,
+								       connector,
+								       mode);
+				if (ret)
+					return ret;
+			} else {
+				return -EINVAL;
+			}
+		}
+	}
+
+	mode->xres = xres;
+	mode->yres = yres;
+	mode->cvt = cvt;
+	mode->rb = rb;
+
+	return 0;
+}
+
 /**
  * drm_mode_parse_command_line_for_connector - parse command line modeline for connector
  * @mode_option: optional per connector mode option
@@ -1434,13 +1580,12 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 					       struct drm_cmdline_mode *mode)
 {
 	const char *name;
-	unsigned int namelen;
-	bool res_specified = false, bpp_specified = false, refresh_specified = false;
-	unsigned int xres = 0, yres = 0, bpp = 32, refresh = 0;
-	bool yres_specified = false, cvt = false, rb = false;
-	bool interlace = false, margins = false, was_digit = false;
-	int i;
-	enum drm_connector_force force = DRM_FORCE_UNSPECIFIED;
+	bool parse_extras = false;
+	unsigned int bpp_off = 0, refresh_off = 0;
+	unsigned int mode_end = 0;
+	char *bpp_ptr = NULL, *refresh_ptr = NULL, *extra_ptr = NULL;
+	char *bpp_end_ptr = NULL, *refresh_end_ptr = NULL;
+	int ret;
 
 #ifdef CONFIG_FB
 	if (!mode_option)
@@ -1453,127 +1598,77 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 	}
 
 	name = mode_option;
-	namelen = strlen(name);
-	for (i = namelen-1; i >= 0; i--) {
-		switch (name[i]) {
-		case '@':
-			if (!refresh_specified && !bpp_specified &&
-			    !yres_specified && !cvt && !rb && was_digit) {
-				refresh = simple_strtol(&name[i+1], NULL, 10);
-				refresh_specified = true;
-				was_digit = false;
-			} else
-				goto done;
-			break;
-		case '-':
-			if (!bpp_specified && !yres_specified && !cvt &&
-			    !rb && was_digit) {
-				bpp = simple_strtol(&name[i+1], NULL, 10);
-				bpp_specified = true;
-				was_digit = false;
-			} else
-				goto done;
-			break;
-		case 'x':
-			if (!yres_specified && was_digit) {
-				yres = simple_strtol(&name[i+1], NULL, 10);
-				yres_specified = true;
-				was_digit = false;
-			} else
-				goto done;
-			break;
-		case '0' ... '9':
-			was_digit = true;
-			break;
-		case 'M':
-			if (yres_specified || cvt || was_digit)
-				goto done;
-			cvt = true;
-			break;
-		case 'R':
-			if (yres_specified || cvt || rb || was_digit)
-				goto done;
-			rb = true;
-			break;
-		case 'm':
-			if (cvt || yres_specified || was_digit)
-				goto done;
-			margins = true;
-			break;
-		case 'i':
-			if (cvt || yres_specified || was_digit)
-				goto done;
-			interlace = true;
-			break;
-		case 'e':
-			if (yres_specified || bpp_specified || refresh_specified ||
-			    was_digit || (force != DRM_FORCE_UNSPECIFIED))
-				goto done;
 
-			force = DRM_FORCE_ON;
-			break;
-		case 'D':
-			if (yres_specified || bpp_specified || refresh_specified ||
-			    was_digit || (force != DRM_FORCE_UNSPECIFIED))
-				goto done;
+	if (!isdigit(name[0]))
+		return false;
 
-			if ((connector->connector_type != DRM_MODE_CONNECTOR_DVII) &&
-			    (connector->connector_type != DRM_MODE_CONNECTOR_HDMIB))
-				force = DRM_FORCE_ON;
-			else
-				force = DRM_FORCE_ON_DIGITAL;
-			break;
-		case 'd':
-			if (yres_specified || bpp_specified || refresh_specified ||
-			    was_digit || (force != DRM_FORCE_UNSPECIFIED))
-				goto done;
+	/* Try to locate the bpp and refresh specifiers, if any */
+	bpp_ptr = strchr(name, '-');
+	if (bpp_ptr) {
+		bpp_off = bpp_ptr - name;
+		mode->bpp_specified = true;
+	}
 
-			force = DRM_FORCE_OFF;
-			break;
-		default:
-			goto done;
-		}
+	refresh_ptr = strchr(name, '@');
+	if (refresh_ptr) {
+		refresh_off = refresh_ptr - name;
+		mode->refresh_specified = true;
 	}
 
-	if (i < 0 && yres_specified) {
-		char *ch;
-		xres = simple_strtol(name, &ch, 10);
-		if ((ch != NULL) && (*ch == 'x'))
-			res_specified = true;
-		else
-			i = ch - name;
-	} else if (!yres_specified && was_digit) {
-		/* catch mode that begins with digits but has no 'x' */
-		i = 0;
+	/* Locate the end of the name / resolution, and parse it */
+	if (bpp_ptr && refresh_ptr) {
+		mode_end = min(bpp_off, refresh_off);
+	} else if (bpp_ptr) {
+		mode_end = bpp_off;
+	} else if (refresh_ptr) {
+		mode_end = refresh_off;
+	} else {
+		mode_end = strlen(name);
+		parse_extras = true;
 	}
-done:
-	if (i >= 0) {
-		pr_warn("[drm] parse error at position %i in video mode '%s'\n",
-			i, name);
-		mode->specified = false;
+
+	ret = drm_mode_parse_cmdline_res_mode(name, mode_end,
+					      parse_extras,
+					      connector,
+					      mode);
+	if (ret)
 		return false;
-	}
+	mode->specified = true;
 
-	if (res_specified) {
-		mode->specified = true;
-		mode->xres = xres;
-		mode->yres = yres;
+	if (bpp_ptr) {
+		ret = drm_mode_parse_cmdline_bpp(bpp_ptr, &bpp_end_ptr, mode);
+		if (ret)
+			return false;
 	}
 
-	if (refresh_specified) {
-		mode->refresh_specified = true;
-		mode->refresh = refresh;
+	if (refresh_ptr) {
+		ret = drm_mode_parse_cmdline_refresh(refresh_ptr,
+						     &refresh_end_ptr, mode);
+		if (ret)
+			return false;
 	}
 
-	if (bpp_specified) {
-		mode->bpp_specified = true;
-		mode->bpp = bpp;
+	/*
+	 * Locate the end of the bpp / refresh, and parse the extras
+	 * if relevant
+	 */
+	if (bpp_ptr && refresh_ptr)
+		extra_ptr = max(bpp_end_ptr, refresh_end_ptr);
+	else if (bpp_ptr)
+		extra_ptr = bpp_end_ptr;
+	else if (refresh_ptr)
+		extra_ptr = refresh_end_ptr;
+
+	if (extra_ptr) {
+		int remaining = strlen(name) - (extra_ptr - name);
+
+		/*
+		 * We still have characters to process, while
+		 * we shouldn't have any
+		 */
+		if (remaining > 0)
+			return false;
 	}
-	mode->rb = rb;
-	mode->cvt = cvt;
-	mode->interlace = interlace;
-	mode->margins = margins;
-	mode->force = force;
 
 	return true;
 }