[Intel-gfx] [PATCH 4/4] drm/i915: expose engine availability through sysfs

[Tvrtko Ursulin]

On 16/11/2017 16:00, Lionel Landwerlin wrote:
> This enables userspace to discover the engines available on the GPU.
> Here is the layout :
> 
> /sys/devices/pci0000:00/0000:00:02.0/drm/card0/engines
> ├── bcs0
> │   ├── class
> │   └── instance
> ├── rcs0
> │   ├── class
> │   └── instance
> ├── vcs0
> │   ├── class
> │   ├── hevc

For engine capabilities I was considering two alternatives since I think 
both would be better than stuffing individual files on the same level as 
class and instance.

Option 1:

$ cat vcs0/capabilities
hevc

Essentially a list of tokens similar to the cpu info string in 
/proc/cpuinfo.

Option 2, more subdirectories:

$ ls -1 vcs0/capabilities
hevc

Option 2 might be easier for userspace to parse? But more annoying to 
implement in i915 I think. So not sure.

Otherwise I am quite happy with the sysfs approach. Can't think of any 
real downsides at the moment.

Regards,

Tvrtko

> │   └── instance
> ├── vcs1
> │   ├── class
> │   └── instance
> └── vecs0
>      ├── class
>      └── instance
> 
> Further capabilities can be added later as attributes of each engine.
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.h         |  1 +
>   drivers/gpu/drm/i915/i915_sysfs.c       | 92 +++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/intel_ringbuffer.h |  2 +
>   3 files changed, 95 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 44b807421af8..c4f6e8ecf212 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2749,6 +2749,7 @@ struct drm_i915_private {
>   
>   	struct {
>   		struct intel_topology_kobject kobj;
> +		struct kobject engines_kobj;
>   
>   		struct sysfs_slice {
>   			struct intel_slice_kobject kobj;
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 1d835f164d80..992aeaa91565 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -712,6 +712,92 @@ static void i915_teardown_topology_sysfs(struct drm_i915_private *dev_priv)
>   	kobject_del(&topology_kobj->kobj);
>   }
>   
> +static struct attribute engine_instance_attr = {
> +	.name = "instance",
> +	.mode = 0444,
> +};
> +
> +static struct attribute engine_class_attr = {
> +	.name = "class",
> +	.mode = 0444,
> +};
> +
> +static struct attribute engine_hevc_attr = {
> +	.name = "hevc",
> +	.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, kobj);
> +
> +	if (attr == &engine_instance_attr)
> +		return sprintf(buf, "%hhu\n", engine->uabi_id);
> +	if (attr == &engine_class_attr)
> +		return sprintf(buf, "%hhu\n", engine->uabi_class);
> +	if (attr == &engine_hevc_attr)
> +		return sprintf(buf, "%i\n", INTEL_GEN(engine->i915) >= 8);
> +	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 int i915_setup_engines_sysfs(struct drm_i915_private *dev_priv)
> +{
> +	struct intel_engine_cs *engine;
> +	enum intel_engine_id id;
> +
> +	kobject_init_and_add(&dev_priv->topology.engines_kobj,
> +			     dev_priv->drm.primary->kdev->kobj.ktype,
> +			     &dev_priv->drm.primary->kdev->kobj,
> +			     "engines");
> +
> +	for_each_engine(engine, dev_priv, id) {
> +		int ret;
> +
> +		kobject_init_and_add(&engine->kobj, &engine_type,
> +				     &dev_priv->topology.engines_kobj,
> +				     engine->name);
> +
> +		ret = sysfs_create_file(&engine->kobj, &engine_instance_attr);
> +		if (ret)
> +			return ret;
> +		ret = sysfs_create_file(&engine->kobj, &engine_class_attr);
> +		if (ret)
> +			return ret;
> +		if (engine->id == VCS) {
> +			ret = sysfs_create_file(&engine->kobj, &engine_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->kobj, &engine_instance_attr);
> +		sysfs_remove_file(&engine->kobj, &engine_class_attr);
> +		sysfs_remove_file(&engine->kobj, &engine_hevc_attr);
> +	}
> +
> +	kobject_get(&dev_priv->topology.engines_kobj);
> +	kobject_del(&dev_priv->topology.engines_kobj);
> +}
> +
>   void i915_setup_sysfs(struct drm_i915_private *dev_priv)
>   {
>   	struct device *kdev = dev_priv->drm.primary->kdev;
> @@ -762,6 +848,10 @@ void i915_setup_sysfs(struct drm_i915_private *dev_priv)
>   	if (ret)
>   		DRM_ERROR("Topology sysfs setup failed\n");
>   
> +	ret = i915_setup_engines_sysfs(dev_priv);
> +	if (ret)
> +		DRM_ERROR("Engines sysfs setup failed\n");
> +
>   	i915_setup_error_capture(kdev);
>   }
>   
> @@ -771,6 +861,8 @@ void i915_teardown_sysfs(struct drm_i915_private *dev_priv)
>   
>   	i915_teardown_error_capture(kdev);
>   
> +	i915_teardown_engines_sysfs(dev_priv);
> +
>   	i915_teardown_topology_sysfs(dev_priv);
>   
>   	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 5f96533e5341..0243a9e620da 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -290,6 +290,8 @@ struct intel_engine_cs {
>   	struct drm_i915_private *i915;
>   	char name[INTEL_ENGINE_CS_MAX_NAME];
>   
> +	struct kobject kobj;
> +
>   	enum intel_engine_id id;
>   	unsigned int hw_id;
>   	unsigned int guc_id;
>