[PATCH 2/4] drm/fb-helper: Keep references for the current set of used connectors

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

The fbdev helper code keeps around two lists of connectors. One is the
list of all connectors it could use, and that list already holds
references for all the connectors. However the other list, or rather
lists, is the one actively being used. That list is tracked per-crtc
and currently doesn't hold any extra references. Let's grab those
extra references to avoid oopsing when the connector vanishes. The
list of all possible connectors should get updated when the hpd happens,
but the list of actively used connectors would not get updated until
the next time the fb-helper picks through the set of possible connectors.
And so we need to hang on to the connectors until that time.

Cc: stable at vger.kernel.org
Cc: Carlos Santa <carlos.santa at intel.com>
Cc: Kirill A. Shutemov <kirill at shutemov.name>
Tested-by: Carlos Santa <carlos.santa at intel.com>
Tested-by: Kirill A. Shutemov <kirill at shutemov.name>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97666
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_fb_helper.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index db469d12d195..9ee1dacf97b8 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2090,7 +2090,6 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 	struct drm_fb_helper_crtc **crtcs;
 	struct drm_display_mode **modes;
 	struct drm_fb_offset *offsets;
-	struct drm_mode_set *modeset;
 	bool *enabled;
 	int width, height;
 	int i;
@@ -2139,7 +2138,14 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 	/* need to set the modesets up here for use later */
 	/* fill out the connector<->crtc mappings into the modesets */
 	for (i = 0; i < fb_helper->crtc_count; i++) {
-		modeset = &fb_helper->crtc_info[i].mode_set;
+		struct drm_mode_set *modeset = &fb_helper->crtc_info[i].mode_set;
+		int j;
+
+		for (j = 0; j < modeset->num_connectors; j++) {
+			drm_connector_unreference(modeset->connectors[j]);
+			modeset->connectors[j] = NULL;
+		}
+
 		modeset->num_connectors = 0;
 		modeset->fb = NULL;
 	}
@@ -2148,19 +2154,23 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 		struct drm_display_mode *mode = modes[i];
 		struct drm_fb_helper_crtc *fb_crtc = crtcs[i];
 		struct drm_fb_offset *offset = &offsets[i];
-		modeset = &fb_crtc->mode_set;
+		struct drm_mode_set *modeset = &fb_crtc->mode_set;
 
 		if (mode && fb_crtc) {
+			struct drm_connector *connector =
+				fb_helper->connector_info[i]->connector;
+
 			DRM_DEBUG_KMS("desired mode %s set on crtc %d (%d,%d)\n",
 				      mode->name, fb_crtc->mode_set.crtc->base.id, offset->x, offset->y);
+
 			fb_crtc->desired_mode = mode;
 			fb_crtc->x = offset->x;
 			fb_crtc->y = offset->y;
 			if (modeset->mode)
 				drm_mode_destroy(dev, modeset->mode);
-			modeset->mode = drm_mode_duplicate(dev,
-							   fb_crtc->desired_mode);
-			modeset->connectors[modeset->num_connectors++] = fb_helper->connector_info[i]->connector;
+			modeset->mode = drm_mode_duplicate(dev, fb_crtc->desired_mode);
+			drm_connector_reference(connector);
+			modeset->connectors[modeset->num_connectors++] = connector;
 			modeset->fb = fb_helper->fb;
 			modeset->x = offset->x;
 			modeset->y = offset->y;
@@ -2169,7 +2179,8 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 
 	/* Clear out any old modes if there are no more connected outputs. */
 	for (i = 0; i < fb_helper->crtc_count; i++) {
-		modeset = &fb_helper->crtc_info[i].mode_set;
+		struct drm_mode_set *modeset = &fb_helper->crtc_info[i].mode_set;
+
 		if (modeset->num_connectors == 0) {
 			BUG_ON(modeset->fb);
 			if (modeset->mode)
-- 
2.7.4