[PATCH v2 1/5] drm: add legacy support for using degamma for gamma

[Tomi Valkeinen]

We currently have drm_atomic_helper_legacy_gamma_set() helper which can
be used to handle legacy gamma-set ioctl.
drm_atomic_helper_legacy_gamma_set() sets GAMMA_LUT, and clears
CTM and DEGAMMA_LUT. This works fine on HW where we have either:

degamma -> ctm -> gamma -> out

or

ctm -> gamma -> out

However, if the HW has gamma table before ctm, the atomic property
should be DEGAMMA_LUT, and thus we have:

degamma -> ctm -> out

This is fine for userspace which sets gamma table using the properties,
as the userspace can check for the existence of gamma & degamma, but the
legacy gamma-set ioctl does not work.

This patch adds a new helper, drm_atomic_helper_legacy_degamma_set(),
which can be used instead of drm_atomic_helper_legacy_gamma_set() when
the DEGAMMA_LUT is the underlying property that needs to be set.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 81 ++++++++++++++++++++++-------
 include/drm/drm_atomic_helper.h     |  4 ++
 2 files changed, 65 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index ddd0e3239150..23cbed541dc7 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3499,24 +3499,11 @@ int drm_atomic_helper_page_flip_target(struct drm_crtc *crtc,
 }
 EXPORT_SYMBOL(drm_atomic_helper_page_flip_target);
 
-/**
- * drm_atomic_helper_legacy_gamma_set - set the legacy gamma correction table
- * @crtc: CRTC object
- * @red: red correction table
- * @green: green correction table
- * @blue: green correction table
- * @size: size of the tables
- * @ctx: lock acquire context
- *
- * Implements support for legacy gamma correction table for drivers
- * that support color management through the DEGAMMA_LUT/GAMMA_LUT
- * properties. See drm_crtc_enable_color_mgmt() and the containing chapter for
- * how the atomic color management and gamma tables work.
- */
-int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
-				       u16 *red, u16 *green, u16 *blue,
-				       uint32_t size,
-				       struct drm_modeset_acquire_ctx *ctx)
+static int legacy_gamma_degamma_set(struct drm_crtc *crtc,
+				    u16 *red, u16 *green, u16 *blue,
+				    uint32_t size,
+				    struct drm_modeset_acquire_ctx *ctx,
+				    bool use_degamma)
 {
 	struct drm_device *dev = crtc->dev;
 	struct drm_atomic_state *state;
@@ -3555,9 +3542,11 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
 	}
 
 	/* Reset DEGAMMA_LUT and CTM properties. */
-	replaced  = drm_property_replace_blob(&crtc_state->degamma_lut, NULL);
+	replaced  = drm_property_replace_blob(&crtc_state->degamma_lut,
+					      use_degamma ? blob : NULL);
 	replaced |= drm_property_replace_blob(&crtc_state->ctm, NULL);
-	replaced |= drm_property_replace_blob(&crtc_state->gamma_lut, blob);
+	replaced |= drm_property_replace_blob(&crtc_state->gamma_lut,
+					      use_degamma ? NULL : blob);
 	crtc_state->color_mgmt_changed |= replaced;
 
 	ret = drm_atomic_commit(state);
@@ -3567,8 +3556,60 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
 	drm_property_blob_put(blob);
 	return ret;
 }
+
+/**
+ * drm_atomic_helper_legacy_gamma_set - set the legacy gamma correction table using gamma_lut
+ * @crtc: CRTC object
+ * @red: red correction table
+ * @green: green correction table
+ * @blue: green correction table
+ * @size: size of the tables
+ * @ctx: lock acquire context
+ *
+ * Implements support for legacy gamma correction table for drivers
+ * that support color management through the DEGAMMA_LUT/GAMMA_LUT
+ * properties. See drm_crtc_enable_color_mgmt() and the containing chapter for
+ * how the atomic color management and gamma tables work.
+ *
+ * This function uses GAMMA_LUT property for the gamma table. This function
+ * can be used when the driver exposes either only GAMMA_LUT or both GAMMA_LUT
+ * and DEGAMMA_LUT.
+ */
+int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
+				       u16 *red, u16 *green, u16 *blue,
+				       uint32_t size,
+				       struct drm_modeset_acquire_ctx *ctx)
+{
+	return legacy_gamma_degamma_set(crtc, red, green, blue, size, ctx, false);
+}
 EXPORT_SYMBOL(drm_atomic_helper_legacy_gamma_set);
 
+/**
+ * drm_atomic_helper_legacy_degamma_set - set the legacy gamma correction table using degamma_lut
+ * @crtc: CRTC object
+ * @red: red correction table
+ * @green: green correction table
+ * @blue: green correction table
+ * @size: size of the tables
+ * @ctx: lock acquire context
+ *
+ * Implements support for legacy gamma correction table for drivers
+ * that support color management through the DEGAMMA_LUT/GAMMA_LUT
+ * properties. See drm_crtc_enable_color_mgmt() and the containing chapter for
+ * how the atomic color management and gamma tables work.
+ *
+ * This function uses DEGAMMA_LUT property for the gamma table. This function
+ * can be used when the driver exposes only DEGAMNMA_LUT.
+ */
+int drm_atomic_helper_legacy_degamma_set(struct drm_crtc *crtc,
+					 u16 *red, u16 *green, u16 *blue,
+					 uint32_t size,
+					 struct drm_modeset_acquire_ctx *ctx)
+{
+	return legacy_gamma_degamma_set(crtc, red, green, blue, size, ctx, true);
+}
+EXPORT_SYMBOL(drm_atomic_helper_legacy_degamma_set);
+
 /**
  * drm_atomic_helper_bridge_propagate_bus_fmt() - Propagate output format to
  *						  the input end of a bridge
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 85df04c8e62f..561c78680388 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -151,6 +151,10 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
 				       u16 *red, u16 *green, u16 *blue,
 				       uint32_t size,
 				       struct drm_modeset_acquire_ctx *ctx);
+int drm_atomic_helper_legacy_degamma_set(struct drm_crtc *crtc,
+					 u16 *red, u16 *green, u16 *blue,
+					 uint32_t size,
+					 struct drm_modeset_acquire_ctx *ctx);
 
 /**
  * drm_atomic_crtc_for_each_plane - iterate over planes currently attached to CRTC
-- 
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