All collected together to provide a consistent story in one patch,
instead of the somewhat bumpy refactor-evolution leading to this.
Also some thoughts on what the next steps could be:
- Create a macro called devm_drm_dev_alloc() which essentially wraps
the kzalloc(); devm_drm_dev_init(); drmm_add_final_kfree() combo.
Needs to be a macro since we'll have to do some typeof trickery and
casting to make this fully generic for all drivers that embed struct
drm_device into their own thing.
- A lot of the simple drivers now have essentially just
drm_dev_unplug(); drm_atomic_helper_shutdown(); as their
$bus_driver->remove hook. We could create a devm_mode_config_reset
which sets drm_atomic_helper_shutdown as it's cleanup action, and a
devm_drm_dev_register with drm_dev_unplug as it's cleanup action,
and simple drivers wouldn't have a need for a ->remove function at
all, and we could delete them.
- For more complicated drivers we need drmm_ versions of a _lot_ more
things. All the userspace visible objects (crtc, plane, encoder,
crtc), anything else hanging of those (maybe a drmm_get_edid, at
least for panels and other built-in stuff).
Also some more thoughts on why we're not reusing devm_ with maybe a
fake struct device embedded into the drm_device (we can't use the
kdev, since that's in each drm_minor).
- Code review gets extremely tricky, since every time you see a devm_
you need to carefully check whether the fake device (with the
drm_device lifetim) or the real device (with the lifetim of the
underlying physical device and driver binding) are used. That's not
going to help at all, and we have enormous amounts of drivers who
use devm_ where they really shouldn't. Having different types makes
sure the compiler type checks this for us and ensures correctness.
- The set of functions are very much non-overlapping. E.g.
devm_ioremap makes total sense, drmm_ioremap has the wrong lifetime,
since hw resources need to be cleaned out at driver unbind and wont
outlive that like a drm_device. Similar, but other way round for
drmm_connector_init (which is the only correct version, devm_ for
drm_connector is just buggy). Simply not having the wrong version
again prevents bugs.
Finally I guess this opens a huge todo for all the drivers. I'm
semi-tempted to do a tree-wide s/devm_kzalloc/drmm_kzalloc/ since most
likely that'll fix an enormous amount of bugs and most likely not
cause any issues at all (aside from maybe holding onto memory slightly
too long).
v2:
- Doc improvements from Laurent.
- Also add kerneldoc for the new drmm_add_action_or_reset.
v3:
- Remove kerneldoc for drmm_remove_action.
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
fixup docs
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-52-daniel.vetter@ffwll.ch
Nothing special here, except that this is the first time that we
automatically clean up something that's initialized with an explicit
driver call. But the cleanup was done at the very end of the release
sequence for all drivers, and that's still the case. At least without
more uses of drmm_ through explicit driver calls.
Also for this one we need drmm_kcalloc, so lets add those.
The motivation here is to allow us to remove the explicit calls to
drm_dev_fini() from all drivers.
v2: Sort includes (Laurent)
v3: Motivate the change in the commit message better (Sam)
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-25-daniel.vetter@ffwll.ch
The cleanup here is somewhat tricky, since we can't tell apart the
allocated minor index from 0. So register a cleanup action first, and
if the index allocation fails, unregister that cleanup action again to
avoid bad mistakes.
The kdev for the minor already handles NULL, so no problem there.
Hence add drmm_remove_action() to the drm_managed library.
v2: Make pointer math around void ** consistent with what Laurent
suggested.
v3: Use drmm_add_action_or_reset and remove drmm_remove_action. Noticed
because of some questions from Thomas. This also means we need to move
the drmm_add_action_or_reset helper earlier in the series.
v4: Uh ... fix slightly embarrassing bug CI spotted.
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200324203936.3330994-1-daniel.vetter@ffwll.ch
We need to add a drmm_kstrdup for this, but let's start somewhere.
This is not exactly perfect onion unwinding, but it's jsut a kfree so
doesn't really matter at all.
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-21-daniel.vetter@ffwll.ch
We have lots of these. And the cleanup code tends to be of dubious
quality. The biggest wrong pattern is that developers use devm_, which
ties the release action to the underlying struct device, whereas
all the userspace visible stuff attached to a drm_device can long
outlive that one (e.g. after a hotunplug while userspace has open
files and mmap'ed buffers). Give people what they want, but with more
correctness.
Mostly copied from devres.c, with types adjusted to fit drm_device and
a few simplifications - I didn't (yet) copy over everything. Since
the types don't match code sharing looked like a hopeless endeavour.
For now it's only super simplified, no groups, you can't remove
actions (but kfree exists, we'll need that soon). Plus all specific to
drm_device ofc, including the logging. Which I didn't bother to make
compile-time optional, since none of the other drm logging is compile
time optional either.
One tricky bit here is the chicken&egg between allocating your
drm_device structure and initiliazing it with drm_dev_init. For
perfect onion unwinding we'd need to have the action to kfree the
allocation registered before drm_dev_init registers any of its own
release handlers. But drm_dev_init doesn't know where exactly the
drm_device is emebedded into the overall structure, and by the time it
returns it'll all be too late. And forcing drivers to be able clean up
everything except the one kzalloc is silly.
Work around this by having a very special final_kfree pointer. This
also avoids troubles with the list head possibly disappearing from
underneath us when we release all resources attached to the
drm_device.
v2: Do all the kerneldoc at the end, to avoid lots of fairly pointless
shuffling while getting everything into shape.
v3: Add static to add/del_dr (Neil)
Move typo fix to the right patch (Neil)
v4: Enforce contract for drmm_add_final_kfree:
Use ksize() to check that the drm_device is indeed contained somewhere
in the final kfree(). Because we need that or the entire managed
release logic blows up in a pile of use-after-frees. Motivated by a
discussion with Laurent.
v5: Review from Laurent:
- %zu instead of casting size_t
- header guards
- sorting of includes
- guarding of data assignment if we didn't allocate it for a NULL
pointer
- delete spurious newline
- cast void* data parameter correctly in ->release call, no idea how
this even worked before
v6: Review from Sam
- Add the kerneldoc for the managed sub-struct back in, even if it
doesn't show up in the generated html somehow.
- Explain why __always_inline.
- Fix bisectability around the final kfree() in drm_dev_relase(). This
is just interim code which will disappear again.
- Some whitespace polish.
- Add debug output when drmm_add_action or drmm_kmalloc fail.
v7: My bisectability fix wasn't up to par as noticed by smatch.
v8: Remove unecessary {} around if else
v9: Use kstrdup_const, which requires kfree_const and introducing a free_dr()
helper (Thomas).
v10: kfree_const goes boom on the plain "kmalloc" assignment, somehow
we need to wrap that in kstrdup_const() too!! Also renumber revision
log, I somehow reset it midway thruh.
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Neil Armstrong <narmstrong@baylibre.com
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200324124540.3227396-1-daniel.vetter@ffwll.ch
