dtrm/edid: Allow comma separated edid binaries. (v3)

Allow comma separated filenames in the edid_firmware parameter.

For example:

edid_firmware=eDP-1:edid/1280x480.bin,DP-2:edid/1920x1080.bin

v2: Use strsep() to simplify parsing of comma seperated string. (Matt)
    Move initial bail before strdup. (Matt)
v3: Changed conditionals after while loop to make more readable (Jani)
    Updated kernel-parameters.txt to reflect changes (Jani)

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Bob Paauwe <bob.j.paauwe@intel.com>
[danvet: Flatten else control flow and appease checkpatch.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 42 insertions, 14 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1d6f0459cd7b..caf0fd4cdecd 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -927,11 +927,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         The filter can be disabled or changed to another
                         driver later using sysfs.
 
-        drm_kms_helper.edid_firmware=[<connector>:]<file>
-                        Broken monitors, graphic adapters and KVMs may
-                        send no or incorrect EDID data sets. This parameter
-                        allows to specify an EDID data set in the
-                        /lib/firmware directory that is used instead.
+        drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
+                        Broken monitors, graphic adapters, KVMs and EDIDless
+                        panels may send no or incorrect EDID data sets.
+                        This parameter allows to specify an EDID data sets
+                        in the /lib/firmware directory that are used instead.
                         Generic built-in EDID data sets are used, if one of
                         edid/1024x768.bin, edid/1280x1024.bin,
                         edid/1680x1050.bin, or edid/1920x1080.bin is given
@@ -940,7 +940,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         available in Documentation/EDID/HOWTO.txt. An EDID
                         data set will only be used for a particular connector,
                         if its name and a colon are prepended to the EDID
-                        name.
+                        name. Each connector may use a unique EDID data
+                        set by separating the files with a comma.  An EDID
+                        data set with no connector name will be used for
+                        any connectors not explicitly specified.
 
         dscc4.setup=    [NET]
 
diff --git a/drivers/gpu/drm/drm_edid_load.c b/drivers/gpu/drm/drm_edid_load.c
index c5605fe4907e..1f445e9bd768 100644
--- a/drivers/gpu/drm/drm_edid_load.c
+++ b/drivers/gpu/drm/drm_edid_load.c
@@ -264,20 +264,43 @@ out:
 int drm_load_edid_firmware(struct drm_connector *connector)
 {
         const char *connector_name = connector->name;
-        char *edidname = edid_firmware, *last, *colon;
+        char *edidname, *last, *colon, *fwstr, *edidstr, *fallback = NULL;
         int ret;
         struct edid *edid;
 
-        if (*edidname == '\0')
+        if (edid_firmware[0] == '\0')
                 return 0;
 
-        colon = strchr(edidname, ':');
-        if (colon != NULL) {
-                if (strncmp(connector_name, edidname, colon - edidname))
-                        return 0;
-                edidname = colon + 1;
-                if (*edidname == '\0')
+        /*
+         * If there are multiple edid files specified and separated
+         * by commas, search through the list looking for one that
+         * matches the connector.
+         *
+         * If there's one or more that don't't specify a connector, keep
+         * the last one found one as a fallback.
+         */
+        fwstr = kstrdup(edid_firmware, GFP_KERNEL);
+        edidstr = fwstr;
+
+        while ((edidname = strsep(&edidstr, ","))) {
+                colon = strchr(edidname, ':');
+                if (colon != NULL) {
+                        if (strncmp(connector_name, edidname, colon - edidname))
+                                continue;
+                        edidname = colon + 1;
+                        break;
+                }
+
+                if (*edidname != '\0') /* corner case: multiple ',' */
+                        fallback = edidname;
+        }
+
+        if (!edidname) {
+                if (!fallback) {
+                        kfree(fwstr);
                         return 0;
+                }
+                edidname = fallback;
         }
 
         last = edidname + strlen(edidname) - 1;
@@ -285,6 +308,8 @@ int drm_load_edid_firmware(struct drm_connector *connector)
                 *last = '\0';
 
         edid = edid_load(connector, edidname, connector_name);
+        kfree(fwstr);
+
         if (IS_ERR_OR_NULL(edid))
                 return 0;