[PATCH 00/19] drm: debugfs: Remove all files automatically on cleanup

[Daniel Vetter]

On Mon, Jan 30, 2017 at 09:58:48AM +0100, Thierry Reding wrote:
> On Fri, Jan 27, 2017 at 03:05:46PM +0100, Daniel Vetter wrote:
> > On Fri, Jan 27, 2017 at 10:36:16AM +0100, Thierry Reding wrote:
> > > On Fri, Jan 27, 2017 at 08:49:34AM +0100, Daniel Vetter wrote:
> > > > On Thu, Jan 26, 2017 at 11:56:02PM +0100, Noralf Trønnes wrote:
> > > > > This patchset removes the need for drivers to clean up their debugfs
> > > > > files on exit. It is done automatically in drm_debugfs_cleanup().
> > > > > This funtion is also called should the driver error out in it's
> > > > > drm_driver.debugfs_init callback.
> > > > > 
> > > > > Two drivers still use drm_debugfs_remove_files():
> > > > > - tegra in it's connectors, not sure if I can remove it.
> > > > 
> > > > I read through them, and they're removed on the component device nodes
> > > > stuff. That looks somewhat fishy from a lifetime point of view, and I
> > > > think removing all that code would be better, too.
> > > 
> > > What makes you think that's problematic from a lifetime point of view?
> > > The component device is tied to the DRM device, so these callbacks are
> > > called at the right time.
> > 
> > debugfs is a userspace interface, which should disappear when
> > drm_dev_unregister gets called. I'm not sure at all whether that lines up
> > with the cleanup of all your component nodes, but otoh it's rather
> > academic since you can't hotplug a tegra.
> > 
> > > That said, I think it's safe to remove the other debugfs files from
> > > Tegra. It might not be possible to remove the cleanup functions
> > > altogether, though, because they have to do a special dance involving
> > > kmemdup() drm_debugfs_create_files() and kfree() in order to support
> > > debugfs files for multiple instances of subdevices.
> > 
> > Hm, that entire "do debugfs on the minor" thing makes almost never sense.
> > All the things we have left in modern drivers are either per-fd, or
> > per-device. Nothing of interest is per-minor. Or do you mean something
> > else?
> 
> I'm not sure I understand what you're saying. We have plenty of code
> that adds debugfs files to the connector's debugfs entry. And that's
> within the minor's debugfs root.
> 
> Am I missing something?

Per-connector entries are fine, per-minor imo not. This is a historical
accident, but it also doesn't really hurt anyone. I think it'd make much
more sense to move everything into a per-devices entry (with maybe
backwards compat links from minor to devices). But really, this is 100%
orthogonal to the cleanup here.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch