[PATCH RFC 1/2] drm: add bitmask property type

[Rob Clark]

From: Rob Clark <rob at ti.com>

A bitmask property is similar to an enum.  The enum value is a bit
position (0-63), and valid property values consist of a mask of
zero or more of (1 << enum_val[n]).

TODO: word commit msg better
TODO: maybe "flags" would be a better name for the property type?
---
See https://github.com/robclark/kernel-omap4/commit/970b7bb95993fc43b4977976bf8005dc2e1a4ad3#L6R411
for an example usage.  In this case combinations of "x-invert", "y-invert"
and "xy-flip" can express all possible combinations of rotations of
multiples of 90 degrees plus mirroring.  Which is sufficient for an
xrandr v1.2 rotation support.  For arbitrary transforms in xrandr v1.3
a different property with a transform matrix (if supported by the
driver) should be used.

Note: I've not finished updating libdrm and ddx driver to use this
yet, so other than compile and boot test, you can consider this as
untested.  But I figure that it is at least worthwhile to send as
an RFC at this point to get feedback.

 drivers/gpu/drm/drm_crtc.c |   46 +++++++++++++++++++++++++++++++++++++++++--
 include/drm/drm_crtc.h     |    3 ++
 include/drm/drm_mode.h     |    1 +
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 95c7ab2..2b462f6 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2713,6 +2713,33 @@ struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
 }
 EXPORT_SYMBOL(drm_property_create_enum);
 
+struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
+					 int flags, const char *name,
+					 const struct drm_prop_enum_list *props, int num_values)
+{
+	struct drm_property *property;
+	int i, ret;
+
+	flags |= DRM_MODE_PROP_BITMASK;
+
+	property = drm_property_create(dev, flags, name, num_values);
+	if (!property)
+		return NULL;
+
+	for (i = 0; i < num_values; i++) {
+		ret = drm_property_add_enum(property, i,
+				      props[i].type,
+				      props[i].name);
+		if (ret) {
+			drm_property_destroy(dev, property);
+			return NULL;
+		}
+	}
+
+	return property;
+}
+EXPORT_SYMBOL(drm_property_create_bitmask);
+
 struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
 					 const char *name,
 					 uint64_t min, uint64_t max)
@@ -2737,7 +2764,14 @@ int drm_property_add_enum(struct drm_property *property, int index,
 {
 	struct drm_property_enum *prop_enum;
 
-	if (!(property->flags & DRM_MODE_PROP_ENUM))
+	if (!(property->flags & (DRM_MODE_PROP_ENUM | DRM_MODE_PROP_BITMASK)))
+		return -EINVAL;
+
+	/*
+	 * Bitmask enum properties have the additional constraint of values
+	 * from 0 to 63
+	 */
+	if ((property->flags & DRM_MODE_PROP_BITMASK) && (value > 63))
 		return -EINVAL;
 
 	if (!list_empty(&property->enum_blob_list)) {
@@ -2881,7 +2915,7 @@ int drm_mode_getproperty_ioctl(struct drm_device *dev,
 	}
 	property = obj_to_property(obj);
 
-	if (property->flags & DRM_MODE_PROP_ENUM) {
+	if (property->flags & (DRM_MODE_PROP_ENUM | DRM_MODE_PROP_BITMASK)) {
 		list_for_each_entry(prop_enum, &property->enum_blob_list, head)
 			enum_count++;
 	} else if (property->flags & DRM_MODE_PROP_BLOB) {
@@ -2906,7 +2940,7 @@ int drm_mode_getproperty_ioctl(struct drm_device *dev,
 	}
 	out_resp->count_values = value_count;
 
-	if (property->flags & DRM_MODE_PROP_ENUM) {
+	if (property->flags & (DRM_MODE_PROP_ENUM | DRM_MODE_PROP_BITMASK)) {
 		if ((out_resp->count_enum_blobs >= enum_count) && enum_count) {
 			copied = 0;
 			enum_ptr = (struct drm_mode_property_enum __user *)(unsigned long)out_resp->enum_blob_ptr;
@@ -3063,6 +3097,12 @@ static bool drm_property_change_is_valid(struct drm_property *property,
 		if (value > property->values[1])
 			return false;
 		return true;
+	} else if (property->flags & DRM_MODE_PROP_BITMASK) {
+		int i;
+		__u64 valid_mask = 0;
+		for (i = 0; i < property->num_values; i++)
+			valid_mask |= (1 << property->values[i]);
+		return !(value & ~valid_mask);
 	} else {
 		int i;
 		for (i = 0; i < property->num_values; i++)
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 32e9c51..28e9a78 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -940,6 +940,9 @@ extern struct drm_property *drm_property_create_enum(struct drm_device *dev, int
 					 const char *name,
 					 const struct drm_prop_enum_list *props,
 					 int num_values);
+struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
+					 int flags, const char *name,
+					 const struct drm_prop_enum_list *props, int num_values);
 struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
 					 const char *name,
 					 uint64_t min, uint64_t max);
diff --git a/include/drm/drm_mode.h b/include/drm/drm_mode.h
index de5de2a..3190dfe 100644
--- a/include/drm/drm_mode.h
+++ b/include/drm/drm_mode.h
@@ -228,6 +228,7 @@ struct drm_mode_get_connector {
 #define DRM_MODE_PROP_IMMUTABLE	(1<<2)
 #define DRM_MODE_PROP_ENUM	(1<<3) /* enumerated type with text strings */
 #define DRM_MODE_PROP_BLOB	(1<<4)
+#define DRM_MODE_PROP_BITMASK	(1<<5) /* bitmask of enumerated types */
 
 struct drm_mode_property_enum {
 	__u64 value;
-- 
1.7.9.1