[PATCH 2/4] drm/modes: Fix the command line parser to take force options into account

[Maxime Ripard]

From: Maxime Ripard <maxime.ripard at bootlin.com>

The command line parser when it has been rewritten introduced a regression
when the only thing on the command line is an option to force the detection
of a connector (such as video=HDMI-A-1:d), which are completely valid.

It's been further broken by the support for the named modes which take
anything that is not a resolution as a named mode.

Let's fix this by running the extra command line option parser on the named
modes if they only take a single character.

Fixes: e08ab74bd4c7 ("drm/modes: Rewrite the command line parser")
Reported-by: Jernej Škrabec <jernej.skrabec at gmail.com>
Reported-by: Thomas Graichen <thomas.graichen at googlemail.com>
Signed-off-by: Maxime Ripard <maxime.ripard at bootlin.com>
---
 drivers/gpu/drm/drm_modes.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index e5997f35b779..ea7e6c8c8318 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1733,16 +1733,30 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 	 * bunch of things:
 	 *   - We need to make sure that the first character (which
 	 *     would be our resolution in X) is a digit.
-	 *   - However, if the X resolution is missing, then we end up
-	 *     with something like x<yres>, with our first character
-	 *     being an alpha-numerical character, which would be
-	 *     considered a named mode.
+	 *   - If not, then it's either a named mode or a force on/off.
+	 *     To distinguish between the two, we need to run the
+	 *     extra parsing function, and if not, then we consider it
+	 *     a named mode.
 	 *
 	 * If this isn't enough, we should add more heuristics here,
 	 * and matching unit-tests.
 	 */
-	if (!isdigit(name[0]) && name[0] != 'x')
+	if (!isdigit(name[0]) && name[0] != 'x') {
+		unsigned int namelen = strlen(name);
+
+		/*
+		 * Only the force on/off options can be in that case,
+		 * and they all take a single character.
+		 */
+		if (namelen == 1) {
+			ret = drm_mode_parse_cmdline_extra(name, namelen, true,
+							   connector, mode);
+			if (!ret)
+				return true;
+		}
+
 		named_mode = true;
+	}
 
 	/* Try to locate the bpp and refresh specifiers, if any */
 	bpp_ptr = strchr(name, '-');
-- 
2.21.0