drm/modes: Fix the command line parser to take force options into account

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@gmail.com>
Reported-by: Thomas Graichen <thomas.graichen@googlemail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Thomas Graichen <thomas.graichen@gmail.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190827115850.25731-2-mripard@kernel.org

1 files changed, 19 insertions, 5 deletions

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 3d10425f6b18..27fe410bba5c 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, '-');