On Wed, Nov 19, 2014 at 05:47:09PM -0200, Paulo Zanoni wrote:
From: Paulo Zanoni paulo.r.zanoni@intel.com
The i915.ko driver needs a way to schedule certain functions to run after some amount of vblanks. There are many different pieces of the driver which could benefit from that.
Since what we want is essentially the vblank ioctl, this patch does the minimum change required to allow this ioctl to be called internally. The noticeable thing here is that the drivers pass a callback function, which is called by drm.ko after the specified amount of vblanks passes.
The great benefit of this minimal change is that all the code responsible for taking care of properly emptying the queues (e.g., when the CRTC is disabled) is already there, so we don't need to rewrite it.
The current wait vblank IOCTL is now implemented on top of these changes, and it provides its own callback: send_vblank_event().
Signed-off-by: Paulo Zanoni paulo.r.zanoni@intel.com
...
+int drm_wait_vblank_kernel(struct drm_crtc *crtc, int count, bool absolute,
drm_vblank_callback_t callback,unsigned long user_data)+{
- struct drm_device *dev = crtc->dev;
- union drm_wait_vblank vblwait;
- int type = 0;
- type |= absolute ? _DRM_VBLANK_ABSOLUTE : _DRM_VBLANK_RELATIVE;
- type |= drm_crtc_index(crtc) << _DRM_VBLANK_HIGH_CRTC_SHIFT;
- if (callback)
type |= _DRM_VBLANK_EVENT;
Need some kerneldoc on this function. It looks like if we have a NULL callback this turns into a more general version of drm_wait_one_vblank() that can handle arbitrary delay counts, right? Is there a case where a multi-vblank wait would be useful internal to the kernel? If not, it might be worth just returning failure on that case for now until we have an actual caller.
Matt