[RFC v2 1/2] drm/i915: Engine discovery uAPI

[Tvrtko Ursulin <tursulin@ursulin.net>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Engine discovery uAPI allows userspace to probe for engine
configuration and features without needing to maintain the
internal PCI id based database.

This enables removal of code duplications across userspace
components.

Probing is done via the new DRM_IOCTL_I915_GEM_ENGINE_INFO ioctl
which returns the number and information on the specified engine
class.

Currently only general engine configuration and HEVC feature of
the VCS engine can be probed but the uAPI is designed to be
generic and extensible.

Code is based almost exactly on the earlier proposal on the
topic by Jon Bloomfield. Engine class and instance refactoring
made recently by Daniele Ceraolo Spurio enabled this to be
implemented in an elegant fashion.

To probe configuration userspace sets the engine class it wants
to query (struct drm_i915_gem_engine_info) and provides an array
of drm_i915_engine_info structs which will be filled in by the
driver. Userspace also has to tell i915 how many elements are in
the array, and the driver will report back the total number of
engine instances in any case.

v2:
 * Add a version field and consolidate to one engine count.
   (Chris Wilson)
 * Rename uAPI flags for VCS engines to DRM_I915_ENGINE_CLASS_VIDEO.
   (Gong Zhipeng)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Daniel Charles <daniel.charles@intel.com>
Cc: "Rogozhkin, Dmitry V" <dmitry.v.rogozhkin@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: "Gong, Zhipeng" <zhipeng.gong@intel.com>
Cc: intel-vaapi-media@lists.01.org
Cc: mesa-dev@lists.freedesktop.org
---
 drivers/gpu/drm/i915/i915_drv.c        |  1 +
 drivers/gpu/drm/i915/i915_drv.h        |  3 ++
 drivers/gpu/drm/i915/intel_engine_cs.c | 64 ++++++++++++++++++++++++++++++++++
 include/uapi/drm/i915_drm.h            | 40 +++++++++++++++++++++
 4 files changed, 108 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index c7d68e789642..1a3f0859227b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -2609,6 +2609,7 @@ static const struct drm_ioctl_desc i915_ioctls[] = {
 	DRM_IOCTL_DEF_DRV(I915_GEM_CONTEXT_GETPARAM, i915_gem_context_getparam_ioctl, DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF_DRV(I915_GEM_CONTEXT_SETPARAM, i915_gem_context_setparam_ioctl, DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF_DRV(I915_PERF_OPEN, i915_perf_open_ioctl, DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF_DRV(I915_GEM_ENGINE_INFO, i915_gem_engine_info_ioctl, DRM_RENDER_ALLOW),
 };
 
 static struct drm_driver driver = {
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 357b6c6c2f04..6eed0e854561 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3547,6 +3547,9 @@ i915_gem_context_lookup_timeline(struct i915_gem_context *ctx,
 int i915_perf_open_ioctl(struct drm_device *dev, void *data,
 			 struct drm_file *file);
 
+int i915_gem_engine_info_ioctl(struct drm_device *dev, void *data,
+			       struct drm_file *file);
+
 /* i915_gem_evict.c */
 int __must_check i915_gem_evict_something(struct i915_address_space *vm,
 					  u64 min_size, u64 alignment,
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 82a274b336c5..caed32dbd912 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -25,6 +25,7 @@
 #include "i915_drv.h"
 #include "intel_ringbuffer.h"
 #include "intel_lrc.h"
+#include <uapi/drm/i915_drm.h>
 
 struct engine_class_info {
 	const char *name;
@@ -1187,6 +1188,69 @@ void intel_engines_reset_default_submission(struct drm_i915_private *i915)
 		engine->set_default_submission(engine);
 }
 
+u8 user_class_map[DRM_I915_ENGINE_CLASS_MAX] = {
+	[DRM_I915_ENGINE_CLASS_OTHER] = OTHER_CLASS,
+	[DRM_I915_ENGINE_CLASS_RENDER] = RENDER_CLASS,
+	[DRM_I915_ENGINE_CLASS_COPY] = COPY_ENGINE_CLASS,
+	[DRM_I915_ENGINE_CLASS_VIDEO] = VIDEO_DECODE_CLASS,
+	[DRM_I915_ENGINE_CLASS_VIDEO_ENHANCE] = VIDEO_ENHANCEMENT_CLASS,
+};
+
+int i915_gem_engine_info_ioctl(struct drm_device *dev, void *data,
+			       struct drm_file *file)
+{
+	struct drm_i915_private *i915 = to_i915(dev);
+	struct drm_i915_gem_engine_info *args = data;
+	struct drm_i915_engine_info __user *user_info =
+					u64_to_user_ptr(args->info_ptr);
+	unsigned int info_size = args->num_engines;
+	struct drm_i915_engine_info info;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	u8 class;
+
+	if (args->rsvd)
+		return -EINVAL;
+
+	switch (args->engine_class) {
+	case DRM_I915_ENGINE_CLASS_OTHER:
+	case DRM_I915_ENGINE_CLASS_RENDER:
+	case DRM_I915_ENGINE_CLASS_COPY:
+	case DRM_I915_ENGINE_CLASS_VIDEO:
+	case DRM_I915_ENGINE_CLASS_VIDEO_ENHANCE:
+		class = user_class_map[args->engine_class];
+		break;
+	case DRM_I915_ENGINE_CLASS_MAX:
+	default:
+		return -EINVAL;
+	};
+
+	args->num_engines = 0;
+
+	if (args->version != 1) {
+		args->version = 1;
+		return 0;
+	}
+
+	for_each_engine(engine, i915, id) {
+		if (class != engine->class)
+			continue;
+
+		if (++args->num_engines > info_size)
+			continue;
+
+		memset(&info, 0, sizeof(info));
+		info.instance = engine->instance;
+		if (INTEL_GEN(i915) >= 8 && id == VCS)
+			info.info = DRM_I915_ENGINE_HAS_HEVC;
+
+		if (copy_to_user(user_info++, &info, sizeof(info)))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/mock_engine.c"
 #endif
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index f24a80d2d42e..2ac6667e57ea 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -260,6 +260,7 @@ typedef struct _drm_i915_sarea {
 #define DRM_I915_GEM_CONTEXT_GETPARAM	0x34
 #define DRM_I915_GEM_CONTEXT_SETPARAM	0x35
 #define DRM_I915_PERF_OPEN		0x36
+#define DRM_I915_GEM_ENGINE_INFO	0x37
 
 #define DRM_IOCTL_I915_INIT		DRM_IOW( DRM_COMMAND_BASE + DRM_I915_INIT, drm_i915_init_t)
 #define DRM_IOCTL_I915_FLUSH		DRM_IO ( DRM_COMMAND_BASE + DRM_I915_FLUSH)
@@ -315,6 +316,7 @@ typedef struct _drm_i915_sarea {
 #define DRM_IOCTL_I915_GEM_CONTEXT_GETPARAM	DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_CONTEXT_GETPARAM, struct drm_i915_gem_context_param)
 #define DRM_IOCTL_I915_GEM_CONTEXT_SETPARAM	DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_CONTEXT_SETPARAM, struct drm_i915_gem_context_param)
 #define DRM_IOCTL_I915_PERF_OPEN	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_OPEN, struct drm_i915_perf_open_param)
+#define DRM_IOCTL_I915_GEM_ENGINE_INFO	DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_ENGINE_INFO, struct drm_i915_gem_engine_info)
 
 /* Allow drivers to submit batchbuffers directly to hardware, relying
  * on the security mechanisms provided by hardware.
@@ -1439,6 +1441,44 @@ enum drm_i915_perf_record_type {
 	DRM_I915_PERF_RECORD_MAX /* non-ABI */
 };
 
+enum drm_i915_gem_engine_class {
+	DRM_I915_ENGINE_CLASS_OTHER = 0,
+	DRM_I915_ENGINE_CLASS_RENDER = 1,
+	DRM_I915_ENGINE_CLASS_COPY = 2,
+	DRM_I915_ENGINE_CLASS_VIDEO = 3,
+	DRM_I915_ENGINE_CLASS_VIDEO_ENHANCE = 4,
+	DRM_I915_ENGINE_CLASS_MAX /* non-ABI */
+};
+
+struct drm_i915_engine_info {
+	/** Engine instance number. */
+	__u32	instance;
+	__u32	rsvd;
+
+	/** Engine specific info. */
+#define DRM_I915_ENGINE_HAS_HEVC	BIT(0)
+	__u64 info;
+};
+
+struct drm_i915_gem_engine_info {
+	/** in/out: Protocol version requested/supported. */
+	__u32 version;
+
+	/** in: Engine class to probe (enum drm_i915_gem_engine_class). */
+	__u32 engine_class;
+
+	/**
+	 * in/out: Number of struct drm_i915_engine_info entries in the provided
+	 * @info_ptr array and actual number of supported hardware engines.
+	 */
+	__u32 num_engines;
+	__u32 rsvd;
+
+	/** in/out: Pointer to array of struct i915_engine_info elements. */
+	__u64 info_ptr;
+
+};
+
 #if defined(__cplusplus)
 }
 #endif
-- 
2.9.3

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