diff options
Diffstat (limited to 'drivers/gpu/drm/drm_vblank.c')
| -rw-r--r-- | drivers/gpu/drm/drm_vblank.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 1659b13b178c..27a99c486f02 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -69,6 +69,12 @@ * &drm_driver.max_vblank_count. In that case the vblank core only disables the * vblanks after a timer has expired, which can be configured through the * ``vblankoffdelay`` module parameter. + * + * Drivers for hardware without support for vertical-blanking interrupts + * must not call drm_vblank_init(). For such drivers, atomic helpers will + * automatically generate fake vblank events as part of the display update. + * This functionality also can be controlled by the driver by enabling and + * disabling struct drm_crtc_state.no_vblank. */ /* Retry timestamp calculation up to 3 times to satisfy @@ -502,6 +508,28 @@ err: EXPORT_SYMBOL(drm_vblank_init); /** + * drm_dev_has_vblank - test if vblanking has been initialized for + * a device + * @dev: the device + * + * Drivers may call this function to test if vblank support is + * initialized for a device. For most hardware this means that vblanking + * can also be enabled. + * + * Atomic helpers use this function to initialize + * &drm_crtc_state.no_vblank. See also drm_atomic_helper_check_modeset(). + * + * Returns: + * True if vblanking has been initialized for the given device, false + * otherwise. + */ +bool drm_dev_has_vblank(const struct drm_device *dev) +{ + return dev->num_crtcs != 0; +} +EXPORT_SYMBOL(drm_dev_has_vblank); + +/** * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC * @crtc: which CRTC's vblank waitqueue to retrieve * |