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tools headers UAPI: Sync drm/i915_drm.h with the kernel sources

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To pick the changes in:

  b65a9489730a2494 ("drm/i915/userptr: Probe existence of backing struct pages upon creation")
  ee242ca704d38699 ("drm/i915/guc: Implement GuC priority management")
  81340cf3bddded4f ("drm/i915/uapi: reject set_domain for discrete")
  7961c5b60f23dff5 ("drm/i915: Add TTM offset argument to mmap.")
  aef7b67a79564f6c ("drm/i915/uapi: convert drm_i915_gem_userptr to kernel doc")
  e7737b67ab46ee0e ("drm/i915/uapi: reject caching ioctls for discrete")
  3aa8c57fe25a9247 ("drm/i915/uapi: convert drm_i915_gem_set_domain to kernel doc")
  289f5a72009b8f67 ("drm/i915/uapi: convert drm_i915_gem_caching to kernel doc")
  4a766ae40ec83301 ("drm/i915: Drop the CONTEXT_CLONE API (v2)")
  6ff6d61dd2a943bd ("drm/i915: Drop I915_CONTEXT_PARAM_NO_ZEROMAP")
  fe4751c3d513ff4f ("drm/i915: Drop I915_CONTEXT_PARAM_RINGSIZE")
  577729533cdc4e37 ("drm/i915: Document the Virtual Engine uAPI")
  c649432e86ca677d ("drm/i915: Fix busy ioctl commentary")

That doesn't result in any changes to tooling as no new ioctl were
added (at least not perceived by tools/perf/trace/beauty/drm_ioctl.sh).

Addressing this perf build warning:

  Warning: Kernel ABI header at 'tools/include/uapi/drm/i915_drm.h' differs from latest version at 'include/uapi/drm/i915_drm.h'
  diff -u tools/include/uapi/drm/i915_drm.h include/uapi/drm/i915_drm.h

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2021-09-11 16:18:28 -03:00
parent 2bae3e64ec
commit 4dc24d7cf4
1 changed files with 414 additions and 78 deletions
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492
tools/include/uapi/drm/i915_drm.h
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@ -572,6 +572,15 @@ typedef struct drm_i915_irq_wait {
#define I915_SCHEDULER_CAP_PREEMPTION (1ul << 2)
#define I915_SCHEDULER_CAP_SEMAPHORES (1ul << 3)
#define I915_SCHEDULER_CAP_ENGINE_BUSY_STATS (1ul << 4)
/*
* Indicates the 2k user priority levels are statically mapped into 3 buckets as
* follows:
*
* -1k to -1 Low priority
* 0 Normal priority
* 1 to 1k Highest priority
*/
#define I915_SCHEDULER_CAP_STATIC_PRIORITY_MAP (1ul << 5)
#define I915_PARAM_HUC_STATUS 42
@ -674,6 +683,9 @@ typedef struct drm_i915_irq_wait {
*/
#define I915_PARAM_HAS_EXEC_TIMELINE_FENCES 55
/* Query if the kernel supports the I915_USERPTR_PROBE flag. */
#define I915_PARAM_HAS_USERPTR_PROBE 56
/* Must be kept compact -- no holes and well documented */
typedef struct drm_i915_getparam {
@ -849,45 +861,113 @@ struct drm_i915_gem_mmap_gtt {
__u64 offset;
};
/**
* struct drm_i915_gem_mmap_offset - Retrieve an offset so we can mmap this buffer object.
*
* This struct is passed as argument to the `DRM_IOCTL_I915_GEM_MMAP_OFFSET` ioctl,
* and is used to retrieve the fake offset to mmap an object specified by &handle.
*
* The legacy way of using `DRM_IOCTL_I915_GEM_MMAP` is removed on gen12+.
* `DRM_IOCTL_I915_GEM_MMAP_GTT` is an older supported alias to this struct, but will behave
* as setting the &extensions to 0, and &flags to `I915_MMAP_OFFSET_GTT`.
*/
struct drm_i915_gem_mmap_offset {
/** Handle for the object being mapped. */
/** @handle: Handle for the object being mapped. */
__u32 handle;
/** @pad: Must be zero */
__u32 pad;
/**
* Fake offset to use for subsequent mmap call
* @offset: The fake offset to use for subsequent mmap call
*
* This is a fixed-size type for 32/64 compatibility.
*/
__u64 offset;
/**
* Flags for extended behaviour.
* @flags: Flags for extended behaviour.
*
* It is mandatory that one of the MMAP_OFFSET types
* (GTT, WC, WB, UC, etc) should be included.
* It is mandatory that one of the `MMAP_OFFSET` types
* should be included:
*
* - `I915_MMAP_OFFSET_GTT`: Use mmap with the object bound to GTT. (Write-Combined)
* - `I915_MMAP_OFFSET_WC`: Use Write-Combined caching.
* - `I915_MMAP_OFFSET_WB`: Use Write-Back caching.
* - `I915_MMAP_OFFSET_FIXED`: Use object placement to determine caching.
*
* On devices with local memory `I915_MMAP_OFFSET_FIXED` is the only valid
* type. On devices without local memory, this caching mode is invalid.
*
* As caching mode when specifying `I915_MMAP_OFFSET_FIXED`, WC or WB will
* be used, depending on the object placement on creation. WB will be used
* when the object can only exist in system memory, WC otherwise.
*/
__u64 flags;
#define I915_MMAP_OFFSET_GTT 0
#define I915_MMAP_OFFSET_WC 1
#define I915_MMAP_OFFSET_WB 2
#define I915_MMAP_OFFSET_UC 3
/*
* Zero-terminated chain of extensions.
#define I915_MMAP_OFFSET_GTT 0
#define I915_MMAP_OFFSET_WC 1
#define I915_MMAP_OFFSET_WB 2
#define I915_MMAP_OFFSET_UC 3
#define I915_MMAP_OFFSET_FIXED 4
/**
* @extensions: Zero-terminated chain of extensions.
*
* No current extensions defined; mbz.
*/
__u64 extensions;
};
/**
* struct drm_i915_gem_set_domain - Adjust the objects write or read domain, in
* preparation for accessing the pages via some CPU domain.
*
* Specifying a new write or read domain will flush the object out of the
* previous domain(if required), before then updating the objects domain
* tracking with the new domain.
*
* Note this might involve waiting for the object first if it is still active on
* the GPU.
*
* Supported values for @read_domains and @write_domain:
*
* - I915_GEM_DOMAIN_WC: Uncached write-combined domain
* - I915_GEM_DOMAIN_CPU: CPU cache domain
* - I915_GEM_DOMAIN_GTT: Mappable aperture domain
*
* All other domains are rejected.
*
* Note that for discrete, starting from DG1, this is no longer supported, and
* is instead rejected. On such platforms the CPU domain is effectively static,
* where we also only support a single &drm_i915_gem_mmap_offset cache mode,
* which can't be set explicitly and instead depends on the object placements,
* as per the below.
*
* Implicit caching rules, starting from DG1:
*
* - If any of the object placements (see &drm_i915_gem_create_ext_memory_regions)
* contain I915_MEMORY_CLASS_DEVICE then the object will be allocated and
* mapped as write-combined only.
*
* - Everything else is always allocated and mapped as write-back, with the
* guarantee that everything is also coherent with the GPU.
*
* Note that this is likely to change in the future again, where we might need
* more flexibility on future devices, so making this all explicit as part of a
* new &drm_i915_gem_create_ext extension is probable.
*/
struct drm_i915_gem_set_domain {
/** Handle for the object */
/** @handle: Handle for the object. */
__u32 handle;
/** New read domains */
/** @read_domains: New read domains. */
__u32 read_domains;
/** New write domain */
/**
* @write_domain: New write domain.
*
* Note that having something in the write domain implies it's in the
* read domain, and only that read domain.
*/
__u32 write_domain;
};
@ -1348,12 +1428,11 @@ struct drm_i915_gem_busy {
* reading from the object simultaneously.
*
* The value of each engine class is the same as specified in the
* I915_CONTEXT_SET_ENGINES parameter and via perf, i.e.
* I915_CONTEXT_PARAM_ENGINES context parameter and via perf, i.e.
* I915_ENGINE_CLASS_RENDER, I915_ENGINE_CLASS_COPY, etc.
* reported as active itself. Some hardware may have parallel
* execution engines, e.g. multiple media engines, which are
* mapped to the same class identifier and so are not separately
* reported for busyness.
* Some hardware may have parallel execution engines, e.g. multiple
* media engines, which are mapped to the same class identifier and so
* are not separately reported for busyness.
*
* Caveat emptor:
* Only the boolean result of this query is reliable; that is whether
@ -1364,43 +1443,79 @@ struct drm_i915_gem_busy {
};
/**
* I915_CACHING_NONE
* struct drm_i915_gem_caching - Set or get the caching for given object
* handle.
*
* GPU access is not coherent with cpu caches. Default for machines without an
* LLC.
*/
#define I915_CACHING_NONE 0
/**
* I915_CACHING_CACHED
* Allow userspace to control the GTT caching bits for a given object when the
* object is later mapped through the ppGTT(or GGTT on older platforms lacking
* ppGTT support, or if the object is used for scanout). Note that this might
* require unbinding the object from the GTT first, if its current caching value
* doesn't match.
*
* GPU access is coherent with cpu caches and furthermore the data is cached in
* last-level caches shared between cpu cores and the gpu GT. Default on
* machines with HAS_LLC.
*/
#define I915_CACHING_CACHED 1
/**
* I915_CACHING_DISPLAY
* Note that this all changes on discrete platforms, starting from DG1, the
* set/get caching is no longer supported, and is now rejected. Instead the CPU
* caching attributes(WB vs WC) will become an immutable creation time property
* for the object, along with the GTT caching level. For now we don't expose any
* new uAPI for this, instead on DG1 this is all implicit, although this largely
* shouldn't matter since DG1 is coherent by default(without any way of
* controlling it).
*
* Special GPU caching mode which is coherent with the scanout engines.
* Transparently falls back to I915_CACHING_NONE on platforms where no special
* cache mode (like write-through or gfdt flushing) is available. The kernel
* automatically sets this mode when using a buffer as a scanout target.
* Userspace can manually set this mode to avoid a costly stall and clflush in
* the hotpath of drawing the first frame.
* Implicit caching rules, starting from DG1:
*
* - If any of the object placements (see &drm_i915_gem_create_ext_memory_regions)
* contain I915_MEMORY_CLASS_DEVICE then the object will be allocated and
* mapped as write-combined only.
*
* - Everything else is always allocated and mapped as write-back, with the
* guarantee that everything is also coherent with the GPU.
*
* Note that this is likely to change in the future again, where we might need
* more flexibility on future devices, so making this all explicit as part of a
* new &drm_i915_gem_create_ext extension is probable.
*
* Side note: Part of the reason for this is that changing the at-allocation-time CPU
* caching attributes for the pages might be required(and is expensive) if we
* need to then CPU map the pages later with different caching attributes. This
* inconsistent caching behaviour, while supported on x86, is not universally
* supported on other architectures. So for simplicity we opt for setting
* everything at creation time, whilst also making it immutable, on discrete
* platforms.
*/
#define I915_CACHING_DISPLAY 2
struct drm_i915_gem_caching {
/**
* Handle of the buffer to set/get the caching level of. */
* @handle: Handle of the buffer to set/get the caching level.
*/
__u32 handle;
/**
* Cacheing level to apply or return value
* @caching: The GTT caching level to apply or possible return value.
*
* bits0-15 are for generic caching control (i.e. the above defined
* values). bits16-31 are reserved for platform-specific variations
* (e.g. l3$ caching on gen7). */
* The supported @caching values:
*
* I915_CACHING_NONE:
*
* GPU access is not coherent with CPU caches. Default for machines
* without an LLC. This means manual flushing might be needed, if we
* want GPU access to be coherent.
*
* I915_CACHING_CACHED:
*
* GPU access is coherent with CPU caches and furthermore the data is
* cached in last-level caches shared between CPU cores and the GPU GT.
*
* I915_CACHING_DISPLAY:
*
* Special GPU caching mode which is coherent with the scanout engines.
* Transparently falls back to I915_CACHING_NONE on platforms where no
* special cache mode (like write-through or gfdt flushing) is
* available. The kernel automatically sets this mode when using a
* buffer as a scanout target. Userspace can manually set this mode to
* avoid a costly stall and clflush in the hotpath of drawing the first
* frame.
*/
#define I915_CACHING_NONE 0
#define I915_CACHING_CACHED 1
#define I915_CACHING_DISPLAY 2
__u32 caching;
};
@ -1639,6 +1754,10 @@ struct drm_i915_gem_context_param {
__u32 size;
__u64 param;
#define I915_CONTEXT_PARAM_BAN_PERIOD 0x1
/* I915_CONTEXT_PARAM_NO_ZEROMAP has been removed. On the off chance
* someone somewhere has attempted to use it, never re-use this context
* param number.
*/
#define I915_CONTEXT_PARAM_NO_ZEROMAP 0x2
#define I915_CONTEXT_PARAM_GTT_SIZE 0x3
#define I915_CONTEXT_PARAM_NO_ERROR_CAPTURE 0x4
@ -1723,24 +1842,8 @@ struct drm_i915_gem_context_param {
*/
#define I915_CONTEXT_PARAM_PERSISTENCE 0xb
/*
* I915_CONTEXT_PARAM_RINGSIZE:
*
* Sets the size of the CS ringbuffer to use for logical ring contexts. This
* applies a limit of how many batches can be queued to HW before the caller
* is blocked due to lack of space for more commands.
*
* Only reliably possible to be set prior to first use, i.e. during
* construction. At any later point, the current execution must be flushed as
* the ring can only be changed while the context is idle. Note, the ringsize
* can be specified as a constructor property, see
* I915_CONTEXT_CREATE_EXT_SETPARAM, but can also be set later if required.
*
* Only applies to the current set of engine and lost when those engines
* are replaced by a new mapping (see I915_CONTEXT_PARAM_ENGINES).
*
* Must be between 4 - 512 KiB, in intervals of page size [4 KiB].
* Default is 16 KiB.
/* This API has been removed. On the off chance someone somewhere has
* attempted to use it, never re-use this context param number.
*/
#define I915_CONTEXT_PARAM_RINGSIZE 0xc
/* Must be kept compact -- no holes and well documented */
@ -1807,6 +1910,69 @@ struct drm_i915_gem_context_param_sseu {
__u32 rsvd;
};
/**
* DOC: Virtual Engine uAPI
*
* Virtual engine is a concept where userspace is able to configure a set of
* physical engines, submit a batch buffer, and let the driver execute it on any
* engine from the set as it sees fit.
*
* This is primarily useful on parts which have multiple instances of a same
* class engine, like for example GT3+ Skylake parts with their two VCS engines.
*
* For instance userspace can enumerate all engines of a certain class using the
* previously described `Engine Discovery uAPI`_. After that userspace can
* create a GEM context with a placeholder slot for the virtual engine (using
* `I915_ENGINE_CLASS_INVALID` and `I915_ENGINE_CLASS_INVALID_NONE` for class
* and instance respectively) and finally using the
* `I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE` extension place a virtual engine in
* the same reserved slot.
*
* Example of creating a virtual engine and submitting a batch buffer to it:
*
* .. code-block:: C
*
* I915_DEFINE_CONTEXT_ENGINES_LOAD_BALANCE(virtual, 2) = {
* .base.name = I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE,
* .engine_index = 0, // Place this virtual engine into engine map slot 0
* .num_siblings = 2,
* .engines = { { I915_ENGINE_CLASS_VIDEO, 0 },
* { I915_ENGINE_CLASS_VIDEO, 1 }, },
* };
* I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, 1) = {
* .engines = { { I915_ENGINE_CLASS_INVALID,
* I915_ENGINE_CLASS_INVALID_NONE } },
* .extensions = to_user_pointer(&virtual), // Chains after load_balance extension
* };
* struct drm_i915_gem_context_create_ext_setparam p_engines = {
* .base = {
* .name = I915_CONTEXT_CREATE_EXT_SETPARAM,
* },
* .param = {
* .param = I915_CONTEXT_PARAM_ENGINES,
* .value = to_user_pointer(&engines),
* .size = sizeof(engines),
* },
* };
* struct drm_i915_gem_context_create_ext create = {
* .flags = I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS,
* .extensions = to_user_pointer(&p_engines);
* };
*
* ctx_id = gem_context_create_ext(drm_fd, &create);
*
* // Now we have created a GEM context with its engine map containing a
* // single virtual engine. Submissions to this slot can go either to
* // vcs0 or vcs1, depending on the load balancing algorithm used inside
* // the driver. The load balancing is dynamic from one batch buffer to
* // another and transparent to userspace.
*
* ...
* execbuf.rsvd1 = ctx_id;
* execbuf.flags = 0; // Submits to index 0 which is the virtual engine
* gem_execbuf(drm_fd, &execbuf);
*/
/*
* i915_context_engines_load_balance:
*
@ -1883,6 +2049,61 @@ struct i915_context_engines_bond {
struct i915_engine_class_instance engines[N__]; \
} __attribute__((packed)) name__
/**
* DOC: Context Engine Map uAPI
*
* Context engine map is a new way of addressing engines when submitting batch-
* buffers, replacing the existing way of using identifiers like `I915_EXEC_BLT`
* inside the flags field of `struct drm_i915_gem_execbuffer2`.
*
* To use it created GEM contexts need to be configured with a list of engines
* the user is intending to submit to. This is accomplished using the
* `I915_CONTEXT_PARAM_ENGINES` parameter and `struct
* i915_context_param_engines`.
*
* For such contexts the `I915_EXEC_RING_MASK` field becomes an index into the
* configured map.
*
* Example of creating such context and submitting against it:
*
* .. code-block:: C
*
* I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, 2) = {
* .engines = { { I915_ENGINE_CLASS_RENDER, 0 },
* { I915_ENGINE_CLASS_COPY, 0 } }
* };
* struct drm_i915_gem_context_create_ext_setparam p_engines = {
* .base = {
* .name = I915_CONTEXT_CREATE_EXT_SETPARAM,
* },
* .param = {
* .param = I915_CONTEXT_PARAM_ENGINES,
* .value = to_user_pointer(&engines),
* .size = sizeof(engines),
* },
* };
* struct drm_i915_gem_context_create_ext create = {
* .flags = I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS,
* .extensions = to_user_pointer(&p_engines);
* };
*
* ctx_id = gem_context_create_ext(drm_fd, &create);
*
* // We have now created a GEM context with two engines in the map:
* // Index 0 points to rcs0 while index 1 points to bcs0. Other engines
* // will not be accessible from this context.
*
* ...
* execbuf.rsvd1 = ctx_id;
* execbuf.flags = 0; // Submits to index 0, which is rcs0 for this context
* gem_execbuf(drm_fd, &execbuf);
*
* ...
* execbuf.rsvd1 = ctx_id;
* execbuf.flags = 1; // Submits to index 0, which is bcs0 for this context
* gem_execbuf(drm_fd, &execbuf);
*/
struct i915_context_param_engines {
__u64 extensions; /* linked chain of extension blocks, 0 terminates */
#define I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE 0 /* see i915_context_engines_load_balance */
@ -1901,20 +2122,10 @@ struct drm_i915_gem_context_create_ext_setparam {
struct drm_i915_gem_context_param param;
};
struct drm_i915_gem_context_create_ext_clone {
/* This API has been removed. On the off chance someone somewhere has
* attempted to use it, never re-use this extension number.
*/
#define I915_CONTEXT_CREATE_EXT_CLONE 1
struct i915_user_extension base;
__u32 clone_id;
__u32 flags;
#define I915_CONTEXT_CLONE_ENGINES (1u << 0)
#define I915_CONTEXT_CLONE_FLAGS (1u << 1)
#define I915_CONTEXT_CLONE_SCHEDATTR (1u << 2)
#define I915_CONTEXT_CLONE_SSEU (1u << 3)
#define I915_CONTEXT_CLONE_TIMELINE (1u << 4)
#define I915_CONTEXT_CLONE_VM (1u << 5)
#define I915_CONTEXT_CLONE_UNKNOWN -(I915_CONTEXT_CLONE_VM << 1)
__u64 rsvd;
};
struct drm_i915_gem_context_destroy {
__u32 ctx_id;
@ -1986,14 +2197,69 @@ struct drm_i915_reset_stats {
__u32 pad;
};
/**
* struct drm_i915_gem_userptr - Create GEM object from user allocated memory.
*
* Userptr objects have several restrictions on what ioctls can be used with the
* object handle.
*/
struct drm_i915_gem_userptr {
/**
* @user_ptr: The pointer to the allocated memory.
*
* Needs to be aligned to PAGE_SIZE.
*/
__u64 user_ptr;
/**
* @user_size:
*
* The size in bytes for the allocated memory. This will also become the
* object size.
*
* Needs to be aligned to PAGE_SIZE, and should be at least PAGE_SIZE,
* or larger.
*/
__u64 user_size;
/**
* @flags:
*
* Supported flags:
*
* I915_USERPTR_READ_ONLY:
*
* Mark the object as readonly, this also means GPU access can only be
* readonly. This is only supported on HW which supports readonly access
* through the GTT. If the HW can't support readonly access, an error is
* returned.
*
* I915_USERPTR_PROBE:
*
* Probe the provided @user_ptr range and validate that the @user_ptr is
* indeed pointing to normal memory and that the range is also valid.
* For example if some garbage address is given to the kernel, then this
* should complain.
*
* Returns -EFAULT if the probe failed.
*
* Note that this doesn't populate the backing pages, and also doesn't
* guarantee that the object will remain valid when the object is
* eventually used.
*
* The kernel supports this feature if I915_PARAM_HAS_USERPTR_PROBE
* returns a non-zero value.
*
* I915_USERPTR_UNSYNCHRONIZED:
*
* NOT USED. Setting this flag will result in an error.
*/
__u32 flags;
#define I915_USERPTR_READ_ONLY 0x1
#define I915_USERPTR_PROBE 0x2
#define I915_USERPTR_UNSYNCHRONIZED 0x80000000
/**
* Returned handle for the object.
* @handle: Returned handle for the object.
*
* Object handles are nonzero.
*/
@ -2376,6 +2642,76 @@ struct drm_i915_query_topology_info {
__u8 data[];
};
/**
* DOC: Engine Discovery uAPI
*
* Engine discovery uAPI is a way of enumerating physical engines present in a
* GPU associated with an open i915 DRM file descriptor. This supersedes the old
* way of using `DRM_IOCTL_I915_GETPARAM` and engine identifiers like
* `I915_PARAM_HAS_BLT`.
*
* The need for this interface came starting with Icelake and newer GPUs, which
* started to establish a pattern of having multiple engines of a same class,
* where not all instances were always completely functionally equivalent.
*
* Entry point for this uapi is `DRM_IOCTL_I915_QUERY` with the
* `DRM_I915_QUERY_ENGINE_INFO` as the queried item id.
*
* Example for getting the list of engines:
*
* .. code-block:: C
*
* struct drm_i915_query_engine_info *info;
* struct drm_i915_query_item item = {
* .query_id = DRM_I915_QUERY_ENGINE_INFO;
* };
* struct drm_i915_query query = {
* .num_items = 1,
* .items_ptr = (uintptr_t)&item,
* };
* int err, i;
*
* // First query the size of the blob we need, this needs to be large
* // enough to hold our array of engines. The kernel will fill out the
* // item.length for us, which is the number of bytes we need.
* //
* // Alternatively a large buffer can be allocated straight away enabling
* // querying in one pass, in which case item.length should contain the
* // length of the provided buffer.
* err = ioctl(fd, DRM_IOCTL_I915_QUERY, &query);
* if (err) ...
*
* info = calloc(1, item.length);
* // Now that we allocated the required number of bytes, we call the ioctl
* // again, this time with the data_ptr pointing to our newly allocated
* // blob, which the kernel can then populate with info on all engines.
* item.data_ptr = (uintptr_t)&info,
*
* err = ioctl(fd, DRM_IOCTL_I915_QUERY, &query);
* if (err) ...
*
* // We can now access each engine in the array
* for (i = 0; i < info->num_engines; i++) {
* struct drm_i915_engine_info einfo = info->engines[i];
* u16 class = einfo.engine.class;
* u16 instance = einfo.engine.instance;
* ....
* }
*
* free(info);
*
* Each of the enumerated engines, apart from being defined by its class and
* instance (see `struct i915_engine_class_instance`), also can have flags and
* capabilities defined as documented in i915_drm.h.
*
* For instance video engines which support HEVC encoding will have the
* `I915_VIDEO_CLASS_CAPABILITY_HEVC` capability bit set.
*
* Engine discovery only fully comes to its own when combined with the new way
* of addressing engines when submitting batch buffers using contexts with
* engine maps configured.
*/
/**
* struct drm_i915_engine_info
*