On Tue, Feb 11, 2020 at 04:47:53PM +0200, Jani Nikula wrote:
There is no real reason to require drivers to set and use dev->dev_private. Indeed, the current recommendation, as documented in drm_device.h, is to embed struct drm_device in the per-device struct instead of using dev_private.
Remove the requirement for dev_private to have been set to indicate driver initialization.
Yeah this is nonsense. Also, drm_irq_install is purely optional semi-midlayer (it's not really a midlayer for the legacy drivers, but whatever, who cares about those).
Now there might be some hilarious races this papers over, but:
- Proper drivers should only call drm_dev_register once everything is set up, including this stuff here. No race possible with anything else really.
- Slightly more wobbly drivers, including the legacy ones, all use drm_global_mutex. This was the former BKL, which means that it was impossible for soeone to go through the load/unload/reload (between lastclose and firstopen) paths and also run the ioctl. But the ioctl had to be made unlocked because blocking there killed X:
commit 8f4ff2b06afcd6f151868474a432c603057eaf56 Author: Ilija Hadzic ihadzic@research.bell-labs.com Date: Mon Oct 31 17:46:18 2011 -0400
drm: do not sleep on vblank while holding a mutex
The even more legacy DRM_CONTROL ioctl stayed fully locked. But the file open/close paths are still fully locked, and that's the only place legacy drivers should call drm_irq_install/uninstall, so should all still be fully ordered and protected and happy.
Feel free to quote or not quote the above in the commit message.
Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Daniel Vetter daniel@ffwll.ch Signed-off-by: Jani Nikula jani.nikula@intel.com
Any ideas for something else drm_irq_install() could/should check to ensure "Driver must have been initialized"?
There are only a few instances of dev_private uses in i915, also to be removed, and we could stop initializing dev_private altogether. We could in fact do that without this patch too, as we don't use drm_irq_install(). But it would be cleaner to not have any checks for driver private stuff outside of drivers.
I hope my review above answers your question here. Patch, as-is:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
drivers/gpu/drm/drm_irq.c | 4 ---- 1 file changed, 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 03bce566a8c3..588be45abd7a 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -111,10 +111,6 @@ int drm_irq_install(struct drm_device *dev, int irq) if (irq == 0) return -EINVAL;
- /* Driver must have been initialized */
- if (!dev->dev_private)
return -EINVAL;- if (dev->irq_enabled) return -EBUSY; dev->irq_enabled = true;
-- 2.20.1