Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 389 insertions, 0 deletions

diff --git a/Documentation/userspace-api/dma-buf-alloc-exchange.rst b/Documentation/userspace-api/dma-buf-alloc-exchange.rst
new file mode 100644
index 000000000..fdff19fce
--- /dev/null
+++ b/Documentation/userspace-api/dma-buf-alloc-exchange.rst
@@ -0,0 +1,389 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. Copyright 2021-2023 Collabora Ltd.
+
+========================
+Exchanging pixel buffers
+========================
+
+As originally designed, the Linux graphics subsystem had extremely limited
+support for sharing pixel-buffer allocations between processes, devices, and
+subsystems. Modern systems require extensive integration between all three
+classes; this document details how applications and kernel subsystems should
+approach this sharing for two-dimensional image data.
+
+It is written with reference to the DRM subsystem for GPU and display devices,
+V4L2 for media devices, and also to Vulkan, EGL and Wayland, for userspace
+support, however any other subsystems should also follow this design and advice.
+
+
+Glossary of terms
+=================
+
+.. glossary::
+
+    image:
+      Conceptually a two-dimensional array of pixels. The pixels may be stored
+      in one or more memory buffers. Has width and height in pixels, pixel
+      format and modifier (implicit or explicit).
+
+    row:
+      A span along a single y-axis value, e.g. from co-ordinates (0,100) to
+      (200,100).
+
+    scanline:
+      Synonym for row.
+
+    column:
+      A span along a single x-axis value, e.g. from co-ordinates (100,0) to
+      (100,100).
+
+    memory buffer:
+      A piece of memory for storing (parts of) pixel data. Has stride and size
+      in bytes and at least one handle in some API. May contain one or more
+      planes.
+
+    plane:
+      A two-dimensional array of some or all of an image's color and alpha
+      channel values.
+
+    pixel:
+      A picture element. Has a single color value which is defined by one or
+      more color channels values, e.g. R, G and B, or Y, Cb and Cr. May also
+      have an alpha value as an additional channel.
+
+    pixel data:
+      Bytes or bits that represent some or all of the color/alpha channel values
+      of a pixel or an image. The data for one pixel may be spread over several
+      planes or memory buffers depending on format and modifier.
+
+    color value:
+      A tuple of numbers, representing a color. Each element in the tuple is a
+      color channel value.
+
+    color channel:
+      One of the dimensions in a color model. For example, RGB model has
+      channels R, G, and B. Alpha channel is sometimes counted as a color
+      channel as well.
+
+    pixel format:
+      A description of how pixel data represents the pixel's color and alpha
+      values.
+
+    modifier:
+      A description of how pixel data is laid out in memory buffers.
+
+    alpha:
+      A value that denotes the color coverage in a pixel. Sometimes used for
+      translucency instead.
+
+    stride:
+      A value that denotes the relationship between pixel-location co-ordinates
+      and byte-offset values. Typically used as the byte offset between two
+      pixels at the start of vertically-consecutive tiling blocks. For linear
+      layouts, the byte offset between two vertically-adjacent pixels. For
+      non-linear formats the stride must be computed in a consistent way, which
+      usually is done as-if the layout was linear.
+
+    pitch:
+      Synonym for stride.
+
+
+Formats and modifiers
+=====================
+
+Each buffer must have an underlying format. This format describes the color
+values provided for each pixel. Although each subsystem has its own format
+descriptions (e.g. V4L2 and fbdev), the ``DRM_FORMAT_*`` tokens should be reused
+wherever possible, as they are the standard descriptions used for interchange.
+These tokens are described in the ``drm_fourcc.h`` file, which is a part of
+DRM's uAPI.
+
+Each ``DRM_FORMAT_*`` token describes the translation between a pixel
+co-ordinate in an image, and the color values for that pixel contained within
+its memory buffers. The number and type of color channels are described:
+whether they are RGB or YUV, integer or floating-point, the size of each channel
+and their locations within the pixel memory, and the relationship between color
+planes.
+
+For example, ``DRM_FORMAT_ARGB8888`` describes a format in which each pixel has
+a single 32-bit value in memory. Alpha, red, green, and blue, color channels are
+available at 8-bit precision per channel, ordered respectively from most to
+least significant bits in little-endian storage. ``DRM_FORMAT_*`` is not
+affected by either CPU or device endianness; the byte pattern in memory is
+always as described in the format definition, which is usually little-endian.
+
+As a more complex example, ``DRM_FORMAT_NV12`` describes a format in which luma
+and chroma YUV samples are stored in separate planes, where the chroma plane is
+stored at half the resolution in both dimensions (i.e. one U/V chroma
+sample is stored for each 2x2 pixel grouping).
+
+Format modifiers describe a translation mechanism between these per-pixel memory
+samples, and the actual memory storage for the buffer. The most straightforward
+modifier is ``DRM_FORMAT_MOD_LINEAR``, describing a scheme in which each plane
+is laid out row-sequentially, from the top-left to the bottom-right corner.
+This is considered the baseline interchange format, and most convenient for CPU
+access.
+
+Modern hardware employs much more sophisticated access mechanisms, typically
+making use of tiled access and possibly also compression. For example, the
+``DRM_FORMAT_MOD_VIVANTE_TILED`` modifier describes memory storage where pixels
+are stored in 4x4 blocks arranged in row-major ordering, i.e. the first tile in
+a plane stores pixels (0,0) to (3,3) inclusive, and the second tile in a plane
+stores pixels (4,0) to (7,3) inclusive.
+
+Some modifiers may modify the number of planes required for an image; for
+example, the ``I915_FORMAT_MOD_Y_TILED_CCS`` modifier adds a second plane to RGB
+formats in which it stores data about the status of every tile, notably
+including whether the tile is fully populated with pixel data, or can be
+expanded from a single solid color.
+
+These extended layouts are highly vendor-specific, and even specific to
+particular generations or configurations of devices per-vendor. For this reason,
+support of modifiers must be explicitly enumerated and negotiated by all users
+in order to ensure a compatible and optimal pipeline, as discussed below.
+
+
+Dimensions and size
+===================
+
+Each pixel buffer must be accompanied by logical pixel dimensions. This refers
+to the number of unique samples which can be extracted from, or stored to, the
+underlying memory storage. For example, even though a 1920x1080
+``DRM_FORMAT_NV12`` buffer has a luma plane containing 1920x1080 samples for the Y
+component, and 960x540 samples for the U and V components, the overall buffer is
+still described as having dimensions of 1920x1080.
+
+The in-memory storage of a buffer is not guaranteed to begin immediately at the
+base address of the underlying memory, nor is it guaranteed that the memory
+storage is tightly clipped to either dimension.
+
+Each plane must therefore be described with an ``offset`` in bytes, which will be
+added to the base address of the memory storage before performing any per-pixel
+calculations. This may be used to combine multiple planes into a single memory
+buffer; for example, ``DRM_FORMAT_NV12`` may be stored in a single memory buffer
+where the luma plane's storage begins immediately at the start of the buffer
+with an offset of 0, and the chroma plane's storage follows within the same buffer
+beginning from the byte offset for that plane.
+
+Each plane must also have a ``stride`` in bytes, expressing the offset in memory
+between two contiguous row. For example, a ``DRM_FORMAT_MOD_LINEAR`` buffer
+with dimensions of 1000x1000 may have been allocated as if it were 1024x1000, in
+order to allow for aligned access patterns. In this case, the buffer will still
+be described with a width of 1000, however the stride will be ``1024 * bpp``,
+indicating that there are 24 pixels at the positive extreme of the x axis whose
+values are not significant.
+
+Buffers may also be padded further in the y dimension, simply by allocating a
+larger area than would ordinarily be required. For example, many media decoders
+are not able to natively output buffers of height 1080, but instead require an
+effective height of 1088 pixels. In this case, the buffer continues to be
+described as having a height of 1080, with the memory allocation for each buffer
+being increased to account for the extra padding.
+
+
+Enumeration
+===========
+
+Every user of pixel buffers must be able to enumerate a set of supported formats
+and modifiers, described together. Within KMS, this is achieved with the
+``IN_FORMATS`` property on each DRM plane, listing the supported DRM formats, and
+the modifiers supported for each format. In userspace, this is supported through
+the `EGL_EXT_image_dma_buf_import_modifiers`_ extension entrypoints for EGL, the
+`VK_EXT_image_drm_format_modifier`_ extension for Vulkan, and the
+`zwp_linux_dmabuf_v1`_ extension for Wayland.
+
+Each of these interfaces allows users to query a set of supported
+format+modifier combinations.
+
+
+Negotiation
+===========
+
+It is the responsibility of userspace to negotiate an acceptable format+modifier
+combination for its usage. This is performed through a simple intersection of
+lists. For example, if a user wants to use Vulkan to render an image to be
+displayed on a KMS plane, it must:
+
+ - query KMS for the ``IN_FORMATS`` property for the given plane
+ - query Vulkan for the supported formats for its physical device, making sure
+   to pass the ``VkImageUsageFlagBits`` and ``VkImageCreateFlagBits``
+   corresponding to the intended rendering use
+ - intersect these formats to determine the most appropriate one
+ - for this format, intersect the lists of supported modifiers for both KMS and
+   Vulkan, to obtain a final list of acceptable modifiers for that format
+
+This intersection must be performed for all usages. For example, if the user
+also wishes to encode the image to a video stream, it must query the media API
+it intends to use for encoding for the set of modifiers it supports, and
+additionally intersect against this list.
+
+If the intersection of all lists is an empty list, it is not possible to share
+buffers in this way, and an alternate strategy must be considered (e.g. using
+CPU access routines to copy data between the different uses, with the
+corresponding performance cost).
+
+The resulting modifier list is unsorted; the order is not significant.
+
+
+Allocation
+==========
+
+Once userspace has determined an appropriate format, and corresponding list of
+acceptable modifiers, it must allocate the buffer. As there is no universal
+buffer-allocation interface available at either kernel or userspace level, the
+client makes an arbitrary choice of allocation interface such as Vulkan, GBM, or
+a media API.
+
+Each allocation request must take, at a minimum: the pixel format, a list of
+acceptable modifiers, and the buffer's width and height. Each API may extend
+this set of properties in different ways, such as allowing allocation in more
+than two dimensions, intended usage patterns, etc.
+
+The component which allocates the buffer will make an arbitrary choice of what
+it considers the 'best' modifier within the acceptable list for the requested
+allocation, any padding required, and further properties of the underlying
+memory buffers such as whether they are stored in system or device-specific
+memory, whether or not they are physically contiguous, and their cache mode.
+These properties of the memory buffer are not visible to userspace, however the
+``dma-heaps`` API is an effort to address this.
+
+After allocation, the client must query the allocator to determine the actual
+modifier selected for the buffer, as well as the per-plane offset and stride.
+Allocators are not permitted to vary the format in use, to select a modifier not
+provided within the acceptable list, nor to vary the pixel dimensions other than
+the padding expressed through offset, stride, and size.
+
+Communicating additional constraints, such as alignment of stride or offset,
+placement within a particular memory area, etc, is out of scope of dma-buf,
+and is not solved by format and modifier tokens.
+
+
+Import
+======
+
+To use a buffer within a different context, device, or subsystem, the user
+passes these parameters (format, modifier, width, height, and per-plane offset
+and stride) to an importing API.
+
+Each memory buffer is referred to by a buffer handle, which may be unique or
+duplicated within an image. For example, a ``DRM_FORMAT_NV12`` buffer may have
+the luma and chroma buffers combined into a single memory buffer by use of the
+per-plane offset parameters, or they may be completely separate allocations in
+memory. For this reason, each import and allocation API must provide a separate
+handle for each plane.
+
+Each kernel subsystem has its own types and interfaces for buffer management.
+DRM uses GEM buffer objects (BOs), V4L2 has its own references, etc. These types
+are not portable between contexts, processes, devices, or subsystems.
+
+To address this, ``dma-buf`` handles are used as the universal interchange for
+buffers. Subsystem-specific operations are used to export native buffer handles
+to a ``dma-buf`` file descriptor, and to import those file descriptors into a
+native buffer handle. dma-buf file descriptors can be transferred between
+contexts, processes, devices, and subsystems.
+
+For example, a Wayland media player may use V4L2 to decode a video frame into a
+``DRM_FORMAT_NV12`` buffer. This will result in two memory planes (luma and
+chroma) being dequeued by the user from V4L2. These planes are then exported to
+one dma-buf file descriptor per plane, these descriptors are then sent along
+with the metadata (format, modifier, width, height, per-plane offset and stride)
+to the Wayland server. The Wayland server will then import these file
+descriptors as an EGLImage for use through EGL/OpenGL (ES), a VkImage for use
+through Vulkan, or a KMS framebuffer object; each of these import operations
+will take the same metadata and convert the dma-buf file descriptors into their
+native buffer handles.
+
+Having a non-empty intersection of supported modifiers does not guarantee that
+import will succeed into all consumers; they may have constraints beyond those
+implied by modifiers which must be satisfied.
+
+
+Implicit modifiers
+==================
+
+The concept of modifiers post-dates all of the subsystems mentioned above. As
+such, it has been retrofitted into all of these APIs, and in order to ensure
+backwards compatibility, support is needed for drivers and userspace which do
+not (yet) support modifiers.
+
+As an example, GBM is used to allocate buffers to be shared between EGL for
+rendering and KMS for display. It has two entrypoints for allocating buffers:
+``gbm_bo_create`` which only takes the format, width, height, and a usage token,
+and ``gbm_bo_create_with_modifiers`` which extends this with a list of modifiers.
+
+In the latter case, the allocation is as discussed above, being provided with a
+list of acceptable modifiers that the implementation can choose from (or fail if
+it is not possible to allocate within those constraints). In the former case
+where modifiers are not provided, the GBM implementation must make its own
+choice as to what is likely to be the 'best' layout. Such a choice is entirely
+implementation-specific: some will internally use tiled layouts which are not
+CPU-accessible if the implementation decides that is a good idea through
+whatever heuristic. It is the implementation's responsibility to ensure that
+this choice is appropriate.
+
+To support this case where the layout is not known because there is no awareness
+of modifiers, a special ``DRM_FORMAT_MOD_INVALID`` token has been defined. This
+pseudo-modifier declares that the layout is not known, and that the driver
+should use its own logic to determine what the underlying layout may be.
+
+.. note::
+
+  ``DRM_FORMAT_MOD_INVALID`` is a non-zero value. The modifier value zero is
+  ``DRM_FORMAT_MOD_LINEAR``, which is an explicit guarantee that the image
+  has the linear layout. Care and attention should be taken to ensure that
+  zero as a default value is not mixed up with either no modifier or the linear
+  modifier. Also note that in some APIs the invalid modifier value is specified
+  with an out-of-band flag, like in ``DRM_IOCTL_MODE_ADDFB2``.
+
+There are four cases where this token may be used:
+  - during enumeration, an interface may return ``DRM_FORMAT_MOD_INVALID``, either
+    as the sole member of a modifier list to declare that explicit modifiers are
+    not supported, or as part of a larger list to declare that implicit modifiers
+    may be used
+  - during allocation, a user may supply ``DRM_FORMAT_MOD_INVALID``, either as the
+    sole member of a modifier list (equivalent to not supplying a modifier list
+    at all) to declare that explicit modifiers are not supported and must not be
+    used, or as part of a larger list to declare that an allocation using implicit
+    modifiers is acceptable
+  - in a post-allocation query, an implementation may return
+    ``DRM_FORMAT_MOD_INVALID`` as the modifier of the allocated buffer to declare
+    that the underlying layout is implementation-defined and that an explicit
+    modifier description is not available; per the above rules, this may only be
+    returned when the user has included ``DRM_FORMAT_MOD_INVALID`` as part of the
+    list of acceptable modifiers, or not provided a list
+  - when importing a buffer, the user may supply ``DRM_FORMAT_MOD_INVALID`` as the
+    buffer modifier (or not supply a modifier) to indicate that the modifier is
+    unknown for whatever reason; this is only acceptable when the buffer has
+    not been allocated with an explicit modifier
+
+It follows from this that for any single buffer, the complete chain of operations
+formed by the producer and all the consumers must be either fully implicit or fully
+explicit. For example, if a user wishes to allocate a buffer for use between
+GPU, display, and media, but the media API does not support modifiers, then the
+user **must not** allocate the buffer with explicit modifiers and attempt to
+import the buffer into the media API with no modifier, but either perform the
+allocation using implicit modifiers, or allocate the buffer for media use
+separately and copy between the two buffers.
+
+As one exception to the above, allocations may be 'upgraded' from implicit
+to explicit modifiers. For example, if the buffer is allocated with
+``gbm_bo_create`` (taking no modifiers), the user may then query the modifier with
+``gbm_bo_get_modifier`` and then use this modifier as an explicit modifier token
+if a valid modifier is returned.
+
+When allocating buffers for exchange between different users and modifiers are
+not available, implementations are strongly encouraged to use
+``DRM_FORMAT_MOD_LINEAR`` for their allocation, as this is the universal baseline
+for exchange. However, it is not guaranteed that this will result in the correct
+interpretation of buffer content, as implicit modifier operation may still be
+subject to driver-specific heuristics.
+
+Any new users - userspace programs and protocols, kernel subsystems, etc -
+wishing to exchange buffers must offer interoperability through dma-buf file
+descriptors for memory planes, DRM format tokens to describe the format, DRM
+format modifiers to describe the layout in memory, at least width and height for
+dimensions, and at least offset and stride for each memory plane.
+
+.. _zwp_linux_dmabuf_v1: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/main/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
+.. _VK_EXT_image_drm_format_modifier: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_EXT_image_drm_format_modifier.html
+.. _EGL_EXT_image_dma_buf_import_modifiers: https://registry.khronos.org/EGL/extensions/EXT/EGL_EXT_image_dma_buf_import_modifiers.txt