[PATCH v3 02/10] drm: Add drm_atomic_crtc_state_for_encoder helper

[Sean Paul <sean@poorly.run>]

From: Sean Paul <seanpaul@chromium.org>

This patch adds a helper to tease out the currently connected crtc for
an encoder, along with its state. This follows the same pattern as the
drm_atomic_crtc_*_for_* macros in the atomic helpers. Since the
relationship of crtc:encoder is 1:n, we don't need a loop since there is
only one crtc per encoder.

Instead of splitting this into 3 functions which all do the same thing,
this is presented as one function. Perhaps that's too ugly and it should
be split to:
struct drm_crtc *drm_atomic_crtc_for_encoder(state, encoder);
struct drm_crtc_state *drm_atomic_new_crtc_state_for_encoder(state, encoder);
struct drm_crtc_state *drm_atomic_old_crtc_state_for_encoder(state, encoder);

Suggestions welcome.

Changes in v3:
- Added to the set

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
---
 drivers/gpu/drm/drm_atomic_helper.c | 48 +++++++++++++++++++++++++++++
 include/drm/drm_atomic_helper.h     |  6 ++++
 2 files changed, 54 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 71cc7d6b0644..1f81ca8daad7 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3591,3 +3591,51 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
 	return ret;
 }
 EXPORT_SYMBOL(drm_atomic_helper_legacy_gamma_set);
+
+/**
+ * drm_atomic_crtc_state_for_encoder - Get crtc and new/old state for an encoder
+ * @state: Atomic state
+ * @encoder: The encoder to fetch the crtc information for
+ * @crtc: If not NULL, receives the currently connected crtc
+ * @old_crtc_state: If not NULL, receives the crtc's old state
+ * @new_crtc_state: If not NULL, receives the crtc's new state
+ *
+ * This function finds the crtc which is currently connected to @encoder and
+ * returns it as well as its old and new state. If there is no crtc currently
+ * connected, the function will clear @crtc, @old_crtc_state, @new_crtc_state.
+ *
+ * All of @crtc, @old_crtc_state, and @new_crtc_state are optional.
+ */
+void drm_atomic_crtc_state_for_encoder(struct drm_atomic_state *state,
+				       struct drm_encoder *encoder,
+				       struct drm_crtc **crtc,
+				       struct drm_crtc_state **old_crtc_state,
+				       struct drm_crtc_state **new_crtc_state)
+{
+	struct drm_crtc *tmp_crtc;
+	struct drm_crtc_state *tmp_new_crtc_state, *tmp_old_crtc_state;
+	u32 enc_mask = drm_encoder_mask(encoder);
+	int i;
+
+	for_each_oldnew_crtc_in_state(state, tmp_crtc, tmp_old_crtc_state,
+				      tmp_new_crtc_state, i) {
+		if (!(tmp_new_crtc_state->encoder_mask & enc_mask))
+			continue;
+
+		if (new_crtc_state)
+			*new_crtc_state = tmp_new_crtc_state;
+		if (old_crtc_state)
+			*old_crtc_state = tmp_old_crtc_state;
+		if (crtc)
+			*crtc = tmp_crtc;
+		return;
+	}
+
+	if (new_crtc_state)
+		*new_crtc_state = NULL;
+	if (old_crtc_state)
+		*old_crtc_state = NULL;
+	if (crtc)
+		*crtc = NULL;
+}
+EXPORT_SYMBOL(drm_atomic_crtc_state_for_encoder);
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 58214be3bf3d..2383550a0cc8 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -153,6 +153,12 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
 				       uint32_t size,
 				       struct drm_modeset_acquire_ctx *ctx);
 
+void drm_atomic_crtc_state_for_encoder(struct drm_atomic_state *state,
+				       struct drm_encoder *encoder,
+				       struct drm_crtc **crtc,
+				       struct drm_crtc_state **old_crtc_state,
+				       struct drm_crtc_state **new_crtc_state);
+
 /**
  * drm_atomic_crtc_for_each_plane - iterate over planes currently attached to CRTC
  * @plane: the loop cursor
-- 
Sean Paul, Software Engineer, Google / Chromium OS