Re: [PATCH 2/4] drm/panthor: Add driver IOCTL for setting BO labels

[Boris Brezillon <boris.brezillon@collabora.com>]

On Wed, 19 Mar 2025 13:49:02 +0000
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> Hi Boris,
> 
> On 17.03.2025 08:50, Boris Brezillon wrote:
> > On Sun, 16 Mar 2025 21:51:33 +0000
> > Adrián Larumbe <adrian.larumbe@collabora.com> wrote:
> >  
> > > Allow UM to label a BO for which it possesses a DRM handle.
> > >
> > > Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> > > ---
> > >  drivers/gpu/drm/panthor/panthor_drv.c | 31 +++++++++++++++++++++++++++
> > >  include/uapi/drm/panthor_drm.h        | 14 ++++++++++++
> > >  2 files changed, 45 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> > > index 310bb44abe1a..f41b8946258f 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_drv.c
> > > +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> > > @@ -1330,6 +1330,35 @@ static int panthor_ioctl_vm_get_state(struct drm_device *ddev, void *data,
> > >  	return 0;
> > >  }
> > >
> > > +static int panthor_ioctl_label_bo(struct drm_device *ddev, void *data,
> > > +				  struct drm_file *file)
> > > +{
> > > +	struct drm_panthor_label_bo *args = data;
> > > +	struct drm_gem_object *obj;
> > > +	const char *label;
> > > +	int ret = 0;
> > > +
> > > +	obj = drm_gem_object_lookup(file, args->handle);
> > > +	if (!obj)
> > > +		return -ENOENT;
> > > +
> > > +	if (args->len && args->label) {
> > > +		label = strndup_user(u64_to_user_ptr(args->label), args->len + 1);
> > > +		if (IS_ERR(label)) {
> > > +			ret = PTR_ERR(label);
> > > +			goto err_label;
> > > +		}
> > > +	} else
> > > +		label = NULL;
> > > +
> > > +	panthor_gem_label_bo(obj, label);
> > > +
> > > +err_label:
> > > +	drm_gem_object_put(obj);
> > > +
> > > +	return ret;
> > > +}
> > > +
> > >  static int
> > >  panthor_open(struct drm_device *ddev, struct drm_file *file)
> > >  {
> > > @@ -1399,6 +1428,7 @@ static const struct drm_ioctl_desc panthor_drm_driver_ioctls[] = {
> > >  	PANTHOR_IOCTL(TILER_HEAP_CREATE, tiler_heap_create, DRM_RENDER_ALLOW),
> > >  	PANTHOR_IOCTL(TILER_HEAP_DESTROY, tiler_heap_destroy, DRM_RENDER_ALLOW),
> > >  	PANTHOR_IOCTL(GROUP_SUBMIT, group_submit, DRM_RENDER_ALLOW),
> > > +	PANTHOR_IOCTL(LABEL_BO, label_bo, DRM_RENDER_ALLOW),
> > >  };
> > >
> > >  static int panthor_mmap(struct file *filp, struct vm_area_struct *vma)
> > > @@ -1508,6 +1538,7 @@ static void panthor_debugfs_init(struct drm_minor *minor)
> > >   * - 1.2 - adds DEV_QUERY_GROUP_PRIORITIES_INFO query
> > >   *       - adds PANTHOR_GROUP_PRIORITY_REALTIME priority
> > >   * - 1.3 - adds DRM_PANTHOR_GROUP_STATE_INNOCENT flag
> > > + * - 1.4 - adds DRM_IOCTL_PANTHOR_LABEL_BO ioctl
> > >   */
> > >  static const struct drm_driver panthor_drm_driver = {
> > >  	.driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ |
> > > diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
> > > index 97e2c4510e69..1a7ed567d36a 100644
> > > --- a/include/uapi/drm/panthor_drm.h
> > > +++ b/include/uapi/drm/panthor_drm.h
> > > @@ -127,6 +127,9 @@ enum drm_panthor_ioctl_id {
> > >
> > >  	/** @DRM_PANTHOR_TILER_HEAP_DESTROY: Destroy a tiler heap. */
> > >  	DRM_PANTHOR_TILER_HEAP_DESTROY,
> > > +
> > > +	/** @DRM_PANTHOR_LABEL_BO: Label a BO. */
> > > +	DRM_PANTHOR_LABEL_BO,  
> >
> > DRM_PANTHOR_BO_SET_LABEL to follow the DRM_PANTHOR_<object>_<action>
> > naming scheme used in this file.
> >
> > I'd also be tempted to introduce a DRM_PANTHOR_BO_GET_LABEL ioctl while
> > we're at it.  
> 
> I thought of this too, but I was a bit reluctant because at present there are no UM
> driver users who need this functionality.

I guess the labeling done in mesa could be made to use GEM labels if
the feature is supported. And honestly, I hate the idea of having an
half-baked implementation allowing the user to set a label with no way
to retrieve this label back. Can we at least change the name such that
we can later add a GET_LABEL ioctl?

> 
> > >  };
> > >
> > >  /**
> > > @@ -977,6 +980,15 @@ struct drm_panthor_tiler_heap_destroy {
> > >  	__u32 pad;
> > >  };
> > >
> > > +/**
> > > + * struct drm_panthor_label_bo - Arguments passed to DRM_IOCTL_PANTHOR_LABEL_BO
> > > + */
> > > +struct drm_panthor_label_bo {
> > > +	__u32 handle;
> > > +	__u32 len;
> > > +	__u64 label;  
> >
> > Can you document these fields?
> >  
> > > +};
> > > +
> > >  /**
> > >   * DRM_IOCTL_PANTHOR() - Build a Panthor IOCTL number
> > >   * @__access: Access type. Must be R, W or RW.
> > > @@ -1019,6 +1031,8 @@ enum {
> > >  		DRM_IOCTL_PANTHOR(WR, TILER_HEAP_CREATE, tiler_heap_create),
> > >  	DRM_IOCTL_PANTHOR_TILER_HEAP_DESTROY =
> > >  		DRM_IOCTL_PANTHOR(WR, TILER_HEAP_DESTROY, tiler_heap_destroy),
> > > +	DRM_IOCTL_PANTHOR_LABEL_BO =
> > > +		DRM_IOCTL_PANTHOR(WR, LABEL_BO, label_bo),
> > >  };
> > >
> > >  #if defined(__cplusplus)  
> 
> 
> Adrian Larumbe