Re: [PATCH 2/3] drm: Create a format/modifier blob

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On 17-05-03 14:15:15, Liviu Dudau wrote:
On Tue, May 02, 2017 at 10:14:27PM -0700, Ben Widawsky wrote:
Updated blob layout (Rob, Daniel, Kristian, xerpi)

Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Daniel Stone <daniels@xxxxxxxxxxxxx>
Cc: Kristian H. Kristensen <hoegsberg@xxxxxxxxx>
Signed-off-by: Ben Widawsky <ben@xxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_mode_config.c |   7 +++
 drivers/gpu/drm/drm_plane.c       | 119 ++++++++++++++++++++++++++++++++++++++
 include/drm/drm_mode_config.h     |   6 ++
 include/uapi/drm/drm_mode.h       |  26 +++++++++
 4 files changed, 158 insertions(+)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index d9862259a2a7..6bfbc3839df5 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -337,6 +337,13 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
 		return -ENOMEM;
 	dev->mode_config.gamma_lut_size_property = prop;

+	prop = drm_property_create(dev,
+				   DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB,
+				   "IN_FORMATS", 0);
+	if (!prop)
+		return -ENOMEM;
+	dev->mode_config.modifiers = prop;
+
 	return 0;
 }

diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 286e183891e5..2e89e0e73435 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -62,6 +62,117 @@ static unsigned int drm_num_planes(struct drm_device *dev)
 	return num;
 }

+struct drm_format_modifier_blob {
+#define FORMAT_BLOB_CURRENT 1
+	/* Version of this blob format */
+	u32 version;
+
+	/* Flags */
+	u32 flags;
+
+	/* Number of fourcc formats supported */
+	u32 count_formats;
+
+	/* Where in this blob the formats exist (in bytes) */
+	u32 formats_offset;
+
+	/* Number of drm_format_modifiers */
+	u32 count_modifiers;
+
+	/* Where in this blob the modifiers exist (in bytes) */
+	u32 modifiers_offset;
+
+	/* u32 formats[] */
+	/* struct drm_format_modifier modifiers[] */
+} __packed;
+
+static inline u32 *
+formats_ptr(struct drm_format_modifier_blob *blob)
+{
+	return (u32 *)(((char *)blob) + blob->formats_offset);
+}
+
+static inline struct drm_format_modifier *
+modifiers_ptr(struct drm_format_modifier_blob *blob)
+{
+	return (struct drm_format_modifier *)(((char *)blob) + blob->modifiers_offset);
+}
+
+static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane,
+				 const struct drm_plane_funcs *funcs,
+				 const uint32_t *formats, unsigned int format_count,
+				 const uint64_t *format_modifiers)

Why do you have to pass the format_modifiers again when you have plane->modifiers?
Or the reverse question: why do you need plane->modifiers when you are passing the
modifiers as parameters all the time?


I've dropped most of the parameters here and just used plane->*

+{
+	const struct drm_mode_config *config = &dev->mode_config;
+	const uint64_t *temp_modifiers = format_modifiers;
+	unsigned int format_modifier_count = 0;
+	struct drm_property_blob *blob = NULL;
+	struct drm_format_modifier *mod;
+	size_t blob_size = 0, formats_size, modifiers_size;
+	struct drm_format_modifier_blob *blob_data;
+	int i, j, ret = 0;
+
+	if (format_modifiers)
+		while (*temp_modifiers++ != DRM_FORMAT_MOD_INVALID)
+			format_modifier_count++;
+
+	formats_size = sizeof(__u32) * format_count;
+	if (WARN_ON(!formats_size)) {
+		/* 0 formats are never expected */
+		return 0;
+	}
+
+	modifiers_size =
+		sizeof(struct drm_format_modifier) * format_modifier_count;
+
+	blob_size = ALIGN(sizeof(struct drm_format_modifier_blob), 8);
+	blob_size += ALIGN(formats_size, 8);
+	blob_size += modifiers_size;
+
+	blob = drm_property_create_blob(dev, blob_size, NULL);
+	if (IS_ERR(blob))
+		return -1;
+
+	blob_data = (struct drm_format_modifier_blob *)blob->data;
+	blob_data->version = FORMAT_BLOB_CURRENT;
+	blob_data->count_formats = format_count;
+	blob_data->formats_offset = sizeof(struct drm_format_modifier_blob);
+	blob_data->count_modifiers = format_modifier_count;
+
+	/* Modifiers offset is a pointer to a struct with a 64 bit field so it
+	 * should be naturally aligned to 8B.
+	 */
+	blob_data->modifiers_offset =
+		ALIGN(blob_data->formats_offset + formats_size, 8);
+
+	memcpy(formats_ptr(blob_data), formats, formats_size);
+
+	/* If we can't determine support, just bail */
+	if (!funcs->format_mod_supported)
+		goto done;
+
+	mod = modifiers_ptr(blob_data);
+	for (i = 0; i < format_modifier_count; i++) {
+		for (j = 0; j < format_count; j++) {
+			if (funcs->format_mod_supported(plane, formats[j],
+							format_modifiers[i])) {
+				mod->formats |= 1 << j;
+			}
+		}
+
+		mod->modifier = format_modifiers[i];
+		mod->offset = 0;
+		mod->pad = 0;
+		mod++;
+	}
+
+done:
+	drm_object_attach_property(&plane->base, config->modifiers,
+				   blob->base.id);
+
+	return ret;
+}
+
 /**
  * drm_universal_plane_init - Initialize a new universal plane object
  * @dev: DRM device
@@ -130,6 +241,10 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 		return -ENOMEM;
 	}

+	/* First driver to need more than 64 formats needs to fix this */
+	if (WARN_ON(format_count > 64))
+		return -EINVAL;
+

Applying this patch makes the above check appear twice in drm_universal_plane_init() function.


Fixed. Thanks.

 	if (name) {
 		va_list ap;

@@ -177,6 +292,10 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 		drm_object_attach_property(&plane->base, config->prop_src_h, 0);
 	}

+	if (config->allow_fb_modifiers)
+		create_in_format_blob(dev, plane, funcs, formats, format_count,
+				      format_modifiers);
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_universal_plane_init);
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 42981711189b..03776e659811 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -757,6 +757,12 @@ struct drm_mode_config {
 	 */
 	bool allow_fb_modifiers;

+	/**
+	 * @modifiers: Plane property to list support modifier/format
+	 * combination.

Comment says "Plane property" yet this is struct drm_mode_config.


Yeah, it is a per plane property. It's just in the mode config for blob
creation. AFAICT, all props work this way. It's attached to the plane though:
drm_object_attach_property(&plane->base, config->modifiers, blob->base.id);

What would you like me to change here?


+	 */
+	struct drm_property *modifiers;
+
 	/* cursor size */
 	uint32_t cursor_width, cursor_height;

diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 8c67fc03d53d..dcdd04c55792 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -665,6 +665,32 @@ struct drm_mode_atomic {
 	__u64 user_data;
 };

+struct drm_format_modifier {
+       /* Bitmask of formats in get_plane format list this info applies to. The

You have some unusual indent of the comment here. Also the file uses a different
style for multi-line comments.


Fixed the indent issue. Thanks for spotting that, it was a copy-paste problem on
my end. The file is inconsistent in multiline comments, actually. Not changed
anything there.

+	* offset allows a sliding window of which 64 formats (bits).
+	*
+	* Some examples:
+	* In today's world with < 65 formats, and formats 0, and 2 are
+	* supported
+	* 0x0000000000000005
+	*		  ^-offset = 0, formats = 5
+	*
+	* If the number formats grew to 128, and formats 98-102 are
+	* supported with the modifier:
+	*
+	* 0x0000003c00000000 0000000000000000
+	*		  ^
+	*		  |__offset = 64, formats = 0x3c00000000
+	*
+	*/
+       uint64_t formats;
+       uint32_t offset;
+       uint32_t pad;

s/pad/__pad/ or s/pad/__reserved/ ?


Every other structure in the file with a pad field is called "pad" however, you
made me realize my data types should be __u32 and __u64, those are fixed.

+
+       /* This modifier can be used with the format for this plane. */

I'm having trouble parsing the comment. How about: "The modifier that applies to the
get_plane format list bitmask." ?


Sure. Done.

Best regards,
Liviu

+       uint64_t modifier;
+} __packed;
+
 /**
  * Create a new 'blob' data property, copying length bytes from data pointer,
  * and returning new blob ID.
--
2.12.2

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--
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
\ source code!  /
 ---------------
   ¯\_(ツ)_/¯

--
Ben Widawsky, Intel Open Source Technology Center
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