Re: [PATCH 3/4] drm/i915: expose engine availability through sysfs

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 20/11/2017 12:23, Lionel Landwerlin wrote:
> This enables userspace to discover the engines available on the GPU.
> Here is the layout on a Skylake GT4:
> 
> /sys/devices/pci0000:00/0000:00:02.0/drm/card0/gt

On this one I think Joonas had a concern that it is difficult for
userspace to get to the sysfs root from the drm file descriptor.

Lionel pointed out that for master nodes it is quite easy:

fstat(fd, &st);
sprintf(sysfs_root, "/sys/dev/char/%u:%u", major(st.st_rdev), minor(st.st_rdev));

For render nodes it is trickier in a way that they would have to
additional resolve an unknown master drm card number. For instance:

/sys/dev/char/%u:%u/device/drm/cardX

Where the "X" is unknown.

But, is it even an use case for render nodes to try and get to the
sysfs root of the master card? Are they allowed to do so?

Regards,

Tvrtko


> ├── bcs
> │   └── 0
> │       ├── capabilities
> │       ├── class
> │       └── id
> ├── rcs
> │   └── 0
> │       ├── capabilities
> │       ├── class
> │       └── id
> ├── vcs
> │   ├── 0
> │   │   ├── capabilities
> │   │   │   └── hevc
> │   │   ├── class
> │   │   └── id
> │   └── 1
> │       ├── capabilities
> │       ├── class
> │       └── id
> └── vecs
>      └── 0
>          ├── capabilities
>          ├── class
>          └── id
> 
> Further capabilities can be added later as attributes of each engine.
> 
> v2: Add capabilities sub directory (Tvrtko)
>      Move engines directory to drm/card/gt (Chris)
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.h         |   5 +
>   drivers/gpu/drm/i915/i915_reg.h         |   1 +
>   drivers/gpu/drm/i915/i915_sysfs.c       | 160 ++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/intel_engine_cs.c  |  12 +++
>   drivers/gpu/drm/i915/intel_ringbuffer.h |   4 +
>   5 files changed, 182 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 78c49db4280a..db550322207c 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2729,6 +2729,11 @@ struct drm_i915_private {
>   		} oa;
>   	} perf;
>   
> +	struct {
> +		struct kobject kobj;
> +		struct kobject classes_kobjs[MAX_ENGINE_CLASS];
> +	} gt_topology;
> +
>   	/* Abstract the submission mechanism (legacy ringbuffer or execlists) away */
>   	struct {
>   		void (*resume)(struct drm_i915_private *);
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 96c80fa0fcac..17aecd4fc6aa 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -186,6 +186,7 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
>   #define VIDEO_ENHANCEMENT_CLASS	2
>   #define COPY_ENGINE_CLASS	3
>   #define OTHER_CLASS		4
> +#define MAX_ENGINE_CLASS	5
>   
>   /* PCI config space */
>   
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 791759f632e1..fd04d0b93eaf 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -559,6 +559,160 @@ static void i915_setup_error_capture(struct device *kdev) {}
>   static void i915_teardown_error_capture(struct device *kdev) {}
>   #endif
>   
> +static struct attribute engine_id_attr = {
> +	.name = "id",
> +	.mode = 0444,
> +};
> +
> +static struct attribute engine_class_attr = {
> +	.name = "class",
> +	.mode = 0444,
> +};
> +
> +static ssize_t
> +show_engine_attr(struct kobject *kobj, struct attribute *attr, char *buf)
> +{
> +	struct intel_engine_cs *engine =
> +		container_of(kobj, struct intel_engine_cs, instance_kobj);
> +
> +	if (attr == &engine_id_attr)
> +		return sprintf(buf, "%hhu\n", engine->uabi_id);
> +	if (attr == &engine_class_attr)
> +		return sprintf(buf, "%hhu\n", engine->uabi_class);
> +	return sprintf(buf, "\n");
> +}
> +
> +static const struct sysfs_ops engine_ops = {
> +	.show = show_engine_attr,
> +};
> +
> +static struct kobj_type engine_type = {
> +	.sysfs_ops = &engine_ops,
> +};
> +
> +static struct attribute engine_capability_hevc_attr = {
> +	.name = "hevc",
> +	.mode = 0444,
> +};
> +
> +static ssize_t
> +show_engine_capabilities_attr(struct kobject *kobj, struct attribute *attr, char *buf)
> +{
> +	struct intel_engine_cs *engine =
> +		container_of(kobj, struct intel_engine_cs, capabilities_kobj);
> +
> +	if (attr == &engine_capability_hevc_attr)
> +		return sprintf(buf, "%i\n", INTEL_GEN(engine->i915) >= 8);
> +	return sprintf(buf, "\n");
> +}
> +
> +static const struct sysfs_ops engine_capabilities_ops = {
> +	.show = show_engine_capabilities_attr,
> +};
> +
> +static struct kobj_type engine_capabilities_type = {
> +	.sysfs_ops = &engine_capabilities_ops,
> +};
> +
> +static int i915_setup_engines_sysfs(struct drm_i915_private *dev_priv,
> +				    struct kobject *gt_kobj)
> +{
> +	struct intel_engine_cs *engine_for_class, *engine;
> +	enum intel_engine_id id_for_class, id;
> +	bool registred[MAX_ENGINE_CLASS] = { false, };
> +	int ret;
> +
> +	for_each_engine(engine_for_class, dev_priv, id_for_class) {
> +		struct kobject *engine_class_kobj =
> +			&dev_priv->gt_topology.classes_kobjs[engine_for_class->class];
> +
> +		if (registred[engine_for_class->class])
> +			continue;
> +
> +		registred[engine_for_class->class] = true;
> +
> +		ret = kobject_init_and_add(engine_class_kobj,
> +					   gt_kobj->ktype,
> +					   gt_kobj,
> +					   intel_engine_get_class_name(engine_for_class));
> +		if (ret)
> +			return ret;
> +
> +		for_each_engine(engine, dev_priv, id) {
> +			if (engine->class != engine_for_class->class)
> +				continue;
> +
> +			ret = kobject_init_and_add(&engine->instance_kobj,
> +						   &engine_type,
> +						   engine_class_kobj,
> +						   "%d", engine->instance);
> +			if (ret)
> +				return ret;
> +
> +			ret = sysfs_create_file(&engine->instance_kobj,
> +						&engine_id_attr);
> +			if (ret)
> +				return ret;
> +			ret = sysfs_create_file(&engine->instance_kobj,
> +						&engine_class_attr);
> +			if (ret)
> +				return ret;
> +
> +			ret = kobject_init_and_add(&engine->capabilities_kobj,
> +						   &engine_capabilities_type,
> +						   &engine->instance_kobj,
> +						   "capabilities");
> +			if (ret)
> +				return ret;
> +
> +			if (engine->id == VCS) {
> +				ret = sysfs_create_file(&engine->capabilities_kobj,
> +							&engine_capability_hevc_attr);
> +				if (ret)
> +					return ret;
> +			}
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void i915_teardown_engines_sysfs(struct drm_i915_private *dev_priv)
> +{
> +	struct intel_engine_cs *engine;
> +	enum intel_engine_id id;
> +
> +	for_each_engine(engine, dev_priv, id) {
> +		sysfs_remove_file(&engine->instance_kobj, &engine_id_attr);
> +		sysfs_remove_file(&engine->instance_kobj, &engine_class_attr);
> +		sysfs_remove_file(&engine->capabilities_kobj,
> +				  &engine_capability_hevc_attr);
> +	}
> +}
> +
> +static int i915_setup_gt_sysfs(struct drm_i915_private *dev_priv,
> +			       struct device *kdev)
> +{
> +	int ret;
> +
> +	ret = kobject_init_and_add(&dev_priv->gt_topology.kobj,
> +				   kdev->kobj.ktype,
> +				   &kdev->kobj,
> +				   "gt");
> +	if (ret)
> +		return ret;
> +
> +	return i915_setup_engines_sysfs(dev_priv, &dev_priv->gt_topology.kobj);
> +}
> +
> +static void i915_teardown_gt_sysfs(struct drm_i915_private *dev_priv)
> +{
> +	i915_teardown_engines_sysfs(dev_priv);
> +
> +	kobject_get(&dev_priv->gt_topology.kobj);
> +	kobject_del(&dev_priv->gt_topology.kobj);
> +}
> +
>   void i915_setup_sysfs(struct drm_i915_private *dev_priv)
>   {
>   	struct device *kdev = dev_priv->drm.primary->kdev;
> @@ -605,6 +759,10 @@ void i915_setup_sysfs(struct drm_i915_private *dev_priv)
>   	if (ret)
>   		DRM_ERROR("RPS sysfs setup failed\n");
>   
> +	ret = i915_setup_gt_sysfs(dev_priv, kdev);
> +	if (ret)
> +		DRM_ERROR("GT sysfs setup failed\n");
> +
>   	i915_setup_error_capture(kdev);
>   }
>   
> @@ -614,6 +772,8 @@ void i915_teardown_sysfs(struct drm_i915_private *dev_priv)
>   
>   	i915_teardown_error_capture(kdev);
>   
> +	i915_teardown_gt_sysfs(dev_priv);
> +
>   	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
>   		sysfs_remove_files(&kdev->kobj, vlv_attrs);
>   	else
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 9897c7f78c51..9d82dfbb45db 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -133,6 +133,18 @@ static const struct engine_info intel_engines[] = {
>   	},
>   };
>   
> +/**
> + * intel_engine_get_class_name() - return the name of the class for an engine
> + * @engine: engine
> + *
> + * Return: a string naming the class of the engine
> + */
> +const char *
> +intel_engine_get_class_name(struct intel_engine_cs *engine)
> +{
> +	return intel_engine_classes[engine->class].name;
> +}
> +
>   /**
>    * ___intel_engine_context_size() - return the size of the context for an engine
>    * @dev_priv: i915 device private
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 5f96533e5341..eca6c87a1e06 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -290,6 +290,9 @@ struct intel_engine_cs {
>   	struct drm_i915_private *i915;
>   	char name[INTEL_ENGINE_CS_MAX_NAME];
>   
> +	struct kobject instance_kobj;
> +	struct kobject capabilities_kobj;
> +
>   	enum intel_engine_id id;
>   	unsigned int hw_id;
>   	unsigned int guc_id;
> @@ -924,6 +927,7 @@ gen8_emit_ggtt_write(u32 *cs, u32 value, u32 gtt_offset)
>   	return cs;
>   }
>   
> +const char *intel_engine_get_class_name(struct intel_engine_cs *engine);
>   bool intel_engine_is_idle(struct intel_engine_cs *engine);
>   bool intel_engines_are_idle(struct drm_i915_private *dev_priv);
>   
> 
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