[PATCH 1/2] drm: provide a helper for the encoder possible_crtcs mask

[Thierry Reding <thierry.reding@gmail.com>]

From: Russell King <rmk+kernel@arm.linux.org.uk>

The encoder possible_crtcs mask identifies which CRTCs can be bound to
a particular encoder.  Each bit from bit 0 defines an index in the list
of CRTCs held in the DRM mode_config crtc_list.  Rather than having
drivers trying to track the position of their CRTCs in the list, expose
the code which already exists for calculating the appropriate mask bit
for a CRTC.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
[treding@nvidia.com: add drm_crtc_index(), move to core]
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v2:
- further extract a new drm_crtc_index() function
- move to DRM core (drm_crtc.c)

 drivers/gpu/drm/drm_crtc.c        | 38 ++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_crtc_helper.c | 16 +++-------------
 include/drm/drm_crtc.h            |  2 ++
 3 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 266a01d7f635..fdfa5a0e51d6 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -675,6 +675,44 @@ void drm_crtc_cleanup(struct drm_crtc *crtc)
 EXPORT_SYMBOL(drm_crtc_cleanup);
 
 /**
+ * drm_crtc_index - find the index of a registered CRTC
+ * @crtc: CRTC to find index for
+ *
+ * Given a registered CRTC, return the index of that CRTC within a DRM
+ * device's list of CRTCs. If the CRTC isn't registered, return -1.
+ */
+int drm_crtc_index(struct drm_crtc *crtc)
+{
+	struct drm_crtc *tmp;
+	int index = 0;
+
+	list_for_each_entry(tmp, &crtc->dev->mode_config.crtc_list, head) {
+		if (tmp == crtc)
+			return index;
+
+		index++;
+	}
+
+	return -1;
+}
+EXPORT_SYMBOL(drm_crtc_index);
+
+/**
+ * drm_crtc_mask - find the mask of a registered CRTC
+ * @crtc: CRTC to find mask for
+ *
+ * Given a registered CRTC, return the mask bit of that CRTC for an
+ * encoder's possible_crtcs field.
+ */
+uint32_t drm_crtc_mask(struct drm_crtc *crtc)
+{
+	int i = drm_crtc_index(crtc);
+
+	return i < 0 ? 0 : 1 << i;
+}
+EXPORT_SYMBOL(drm_crtc_mask);
+
+/**
  * drm_mode_probed_add - add a mode to a connector's probed mode list
  * @connector: connector the new mode
  * @mode: mode data
diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 01361aba033b..95b32098badf 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -334,23 +334,13 @@ EXPORT_SYMBOL(drm_helper_disable_unused_functions);
 static bool drm_encoder_crtc_ok(struct drm_encoder *encoder,
 				struct drm_crtc *crtc)
 {
-	struct drm_device *dev;
-	struct drm_crtc *tmp;
-	int crtc_mask = 1;
+	uint32_t crtc_mask;
 
 	WARN(!crtc, "checking null crtc?\n");
 
-	dev = crtc->dev;
-
-	list_for_each_entry(tmp, &dev->mode_config.crtc_list, head) {
-		if (tmp == crtc)
-			break;
-		crtc_mask <<= 1;
-	}
+	crtc_mask = drm_crtc_mask(crtc);
 
-	if (encoder->possible_crtcs & crtc_mask)
-		return true;
-	return false;
+	return !!(encoder->possible_crtcs & crtc_mask);
 }
 
 /*
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index f32c5cd51f41..a61fb73fdcb5 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -929,6 +929,8 @@ extern int drm_crtc_init(struct drm_device *dev,
 			 struct drm_crtc *crtc,
 			 const struct drm_crtc_funcs *funcs);
 extern void drm_crtc_cleanup(struct drm_crtc *crtc);
+extern int drm_crtc_index(struct drm_crtc *crtc);
+extern uint32_t drm_crtc_mask(struct drm_crtc *crtc);
 
 extern void drm_connector_ida_init(void);
 extern void drm_connector_ida_destroy(void);
-- 
1.8.4.2