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 <ihad...@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 <ch...@chris-wilson.co.uk>
> Cc: Daniel Vetter <dan...@ffwll.ch>
> Signed-off-by: Jani Nikula <jani.nik...@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.vet...@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
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
