On Thu, Jun 24, 2021 at 11:07:57AM +0200, Thomas Zimmermann wrote: > Hi > > Am 24.06.21 um 10:51 schrieb Jani Nikula: > > On Thu, 24 Jun 2021, Thomas Zimmermann wrote: > > > Hi > > > > > > Am 24.06.21 um 10:06 schrieb Jani Nikula: > > > > On Thu, 24 Jun 2021, Thomas Zimmermann wrote: > > > > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > > > > > index 3417e1ac7918..10fe16bafcb6 100644 > > > > > --- a/drivers/gpu/drm/drm_vblank.c > > > > > +++ b/drivers/gpu/drm/drm_vblank.c > > > > > @@ -1748,8 +1748,16 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data, > > > > > unsigned int pipe_index; > > > > > unsigned int flags, pipe, high_pipe; > > > > > - if (!dev->irq_enabled) > > > > > - return -EOPNOTSUPP; > > > > > +#if defined(CONFIG_DRM_LEGACY) > > > > > + if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY))) { > > > > > + if (!dev->irq_enabled) > > > > > + return -EOPNOTSUPP; > > > > > + } else /* if DRIVER_MODESET */ > > > > > +#endif > > > > > + { > > > > > + if (!drm_dev_has_vblank(dev)) > > > > > + return -EOPNOTSUPP; > > > > > + } > > > > > > > > Sheesh I hate this kind of inline #ifdefs. > > > > > > > > Two alternate suggestions that I believe should be as just efficient: > > > > > > Or how about: > > > > > > static bool drm_wait_vblank_supported(struct drm_device *dev) > > > > > > { > > > > > > if defined(CONFIG_DRM_LEGACY) > > > if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY))) > > > > > > return dev->irq_enabled; > > > > > > #endif > > > return drm_dev_has_vblank(dev); > > > > > > } > > > > > > > > > ? > > > > > > It's inline, but still readable. > > > > It's definitely better than the original, but it's unclear to me why > > you'd prefer this over option 2) below. I guess the only reason I can > > think of is emphasizing the conditional compilation. However, > > IS_ENABLED() is widely used in this manner specifically to avoid inline > > #if, and the compiler optimizes it away. > > It's simply more readable to me as the condition is simpler. But option 2 is > also ok. Perhaps do something like this, then: if (IS_ENABLED(CONFIG_DRM_LEGACY)) { if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY))) return dev->irq_enabled; } return drm_dev_has_vblank(dev); That's about just as readable as the variant involving the preprocessor but has all the benefits of not using the preprocessor. Thierry