On Sat, Aug 05, 2017 at 12:59:07PM +0200, Noralf Trønnes wrote: > (I had to switch to Daniel's Intel address to get this sent) > > Den 05.08.2017 00.19, skrev Ilia Mirkin: > > On Fri, Aug 4, 2017 at 4:43 PM, Eric Anholt <e...@anholt.net> wrote: > > > Laurent Pinchart <laurent.pinch...@ideasonboard.com> writes: > > > > > > > Hi Eric, > > > > > > > > (CC'ing Daniel) > > > > > > > > Thank you for the patch. > > > > > > > > On Tuesday 18 Jul 2017 14:05:06 Eric Anholt wrote: > > > > > This will let drivers reduce the error cleanup they need, in > > > > > particular the "is_panel_bridge" flag. > > > > > > > > > > v2: Slight cleanup of remove function by Andrzej > > > > I just want to point out that, in the context of Daniel's work on > > > > hot-unplug, > > > > 90% of the devm_* allocations are wrong and will get in the way. All > > > > DRM core > > > > objects that are accessible one way or another from userspace will need > > > > to be > > > > properly reference-counted and freed only when the last reference > > > > disappears, > > > > which could be well after the corresponding device is removed. I > > > > believe this > > > > could be one such objects :-/ > > > Sure, if you're hotplugging, your life is pain. For non-hotpluggable > > > devices, like our SOC platform devices (current panel-bridge consumers), > > > this still seems like an excellent simplification of memory management. > > At that point you may as well make your module non-unloadable, and > > return failure when trying to remove a device from management by the > > driver (whatever the opposite of "probe" is, I forget). Hotplugging > > doesn't only happen when physically removing, it can happen for all > > kinds of reasons... and userspace may still hold references in some of > > those cases. > > If drm_open() gets a ref on dev->dev and puts it in drm_release(), > won't that delay devm_* cleanup until userspace is done?
No. drm_device is the thing that is refcounted for userspace references like open FD (we're not perfect about it, e.g. sysfs and dma-buf/fence don't). devm_ otoh is tied to the lifetime of the underlying device, and that one can get outlived by drm_device. Or at least afaiui, devm_ stuff is nuked on unplug, and not when the final sw reference of the struct device disappears. Not sure tough, it's complicated. -Daniel -- 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
