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  1. Jun 08, 2019
    • Mauro Carvalho Chehab's avatar
      docs: mark orphan documents as such · 27c054d2
      Mauro Carvalho Chehab authored 
      
Sphinx doesn't like orphan documents:

    Documentation/accelerators/ocxl.rst: WARNING: document isn't included in any toctree
    Documentation/arm/stm32/overview.rst: WARNING: document isn't included in any toctree
    Documentation/arm/stm32/stm32f429-overview.rst: WARNING: document isn't included in any toctree
    Documentation/arm/stm32/stm32f746-overview.rst: WARNING: document isn't included in any toctree
    Documentation/arm/stm32/stm32f769-overview.rst: WARNING: document isn't included in any toctree
    Documentation/arm/stm32/stm32h743-overview.rst: WARNING: document isn't included in any toctree
    Documentation/arm/stm32/stm32mp157-overview.rst: WARNING: document isn't included in any toctree
    Documentation/gpu/msm-crash-dump.rst: WARNING: document isn't included in any toctree
    Documentation/interconnect/interconnect.rst: WARNING: document isn't included in any toctree
    Documentation/laptops/lg-laptop.rst: WARNING: document isn't included in any toctree
    Documentation/powerpc/isa-versions.rst: WARNING: document isn't included in any toctree
    Documentation/virtual/kvm/amd-memory-encryption.rst: WARNING: document isn't included in any toctree
    Documentation/virtual/kvm/vcpu-requests.rst: WARNING: document isn't included in any toctree

So, while they aren't on any toctree, add :orphan: to them, in order
to silent this warning.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: default avatarAndrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
      27c054d2
  3. Apr 17, 2019
  5. Apr 05, 2019
  7. Apr 04, 2019
  9. Mar 26, 2019
  11. Mar 14, 2019
  13. Mar 04, 2019
  15. Feb 19, 2019
  17. Feb 11, 2019
  19. Feb 07, 2019
  21. Feb 06, 2019
  23. Jan 31, 2019
  25. Jan 30, 2019
  27. Jan 29, 2019
  29. Jan 17, 2019
  31. Jan 14, 2019
  33. Jan 12, 2019
  35. Jan 11, 2019
    • Daniel Vetter's avatar
      drm/doc: Polish kerneldoc for drm_device.h · 3214a166
      Daniel Vetter authored 
      
- Move all the legacy gunk at the bottom, and exclude it from
  kerneldoc.
- Documentation for the remaining bits.

v2: Fix typo (Sam).

Cc: Sam Ravnborg <sam@ravnborg.org>
Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111164048.29067-5-daniel.vetter@ffwll.ch
      3214a166
    • Brian Starkey's avatar
      drm/afbc: Add AFBC modifier usage documentation · 3affaa5a
      Brian Starkey authored 
      
AFBC is a flexible, proprietary, lossless compression protocol and
format, with a number of defined DRM format modifiers. To facilitate
consistency and compatibility between different AFBC producers and
consumers, document the expectations for usage of the AFBC DRM format
modifiers in a new .rst chapter.

Signed-off-by: default avatarBrian Starkey <brian.starkey@arm.com>
Reviewed-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
[Updated MAINTAINERS entry to show that "Mali DP Maintainers" is
 actually a mailing list and added an SPDX-License-Identifier to
 the documentation]
Signed-off-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
      3affaa5a
    • Lyude Paul's avatar
      drm/dp_mst: Introduce new refcounting scheme for mstbs and ports · ebcc0e6b
      Lyude Paul authored 
      
The current way of handling refcounting in the DP MST helpers is really
confusing and probably just plain wrong because it's been hacked up many
times over the years without anyone actually going over the code and
seeing if things could be simplified.

To the best of my understanding, the current scheme works like this:
drm_dp_mst_port and drm_dp_mst_branch both have a single refcount. When
this refcount hits 0 for either of the two, they're removed from the
topology state, but not immediately freed. Both ports and branch devices
will reinitialize their kref once it's hit 0 before actually destroying
themselves. The intended purpose behind this is so that we can avoid
problems like not being able to free a remote payload that might still
be active, due to us having removed all of the port/branch device
structures in memory, as per:

commit 91a25e46 ("drm/dp/mst: deallocate payload on port destruction")

Which may have worked, but then it caused use-after-free errors. Being
new to MST at the time, I tried fixing it;

commit 263efde3 ("drm/dp/mst: Get validated port ref in drm_dp_update_payload_part1()")

But, that was broken: both drm_dp_mst_port and drm_dp_mst_branch structs
are validated in almost every DP MST helper function. Simply put, this
means we go through the topology and try to see if the given
drm_dp_mst_branch or drm_dp_mst_port is still attached to something
before trying to use it in order to avoid dereferencing freed memory
(something that has happened a LOT in the past with this library).
Because of this it doesn't actually matter whether or not we keep keep
the ports and branches around in memory as that's not enough, because
any function that validates the branches and ports passed to it will
still reject them anyway since they're no longer in the topology
structure. So, use-after-free errors were fixed but payload deallocation
was completely broken.

Two years later, AMD informed me about this issue and I attempted to
come up with a temporary fix, pending a long-overdue cleanup of this
library:

commit c54c7374 ("drm/dp_mst: Skip validating ports during destruction, just ref")

But then that introduced use-after-free errors, so I quickly reverted
it:

commit 9765635b ("Revert "drm/dp_mst: Skip validating ports during destruction, just ref"")

And in the process, learned that there is just no simple fix for this:
the design is just broken. Unfortunately, the usage of these helpers are
quite broken as well. Some drivers like i915 have been smart enough to
avoid accessing any kind of information from MST port structures, but
others like nouveau have assumed, understandably so, that
drm_dp_mst_port structures are normal and can just be accessed at any
time without worrying about use-after-free errors.

After a lot of discussion, me and Daniel Vetter came up with a better
idea to replace all of this.

To summarize, since this is documented far more indepth in the
documentation this patch introduces, we make it so that drm_dp_mst_port
and drm_dp_mst_branch structures have two different classes of
refcounts: topology_kref, and malloc_kref. topology_kref corresponds to
the lifetime of the given drm_dp_mst_port or drm_dp_mst_branch in it's
given topology. Once it hits zero, any associated connectors are removed
and the branch or port can no longer be validated. malloc_kref
corresponds to the lifetime of the memory allocation for the actual
structure, and will always be non-zero so long as the topology_kref is
non-zero. This gives us a way to allow callers to hold onto port and
branch device structures past their topology lifetime, and dramatically
simplifies the lifetimes of both structures. This also finally fixes the
port deallocation problem, properly.

Additionally: since this now means that we can keep ports and branch
devices allocated in memory for however long we need, we no longer need
a significant amount of the port validation that we currently do.

Additionally, there is one last scenario that this fixes, which couldn't
have been fixed properly beforehand:

- CPU1 unrefs port from topology (refcount 1->0)
- CPU2 refs port in topology(refcount 0->1)

Since we now can guarantee memory safety for ports and branches
as-needed, we also can make our main reference counting functions fix
this problem by using kref_get_unless_zero() internally so that topology
refcounts can only ever reach 0 once.

Changes since v4:
* Change the kernel-figure summary for dp-mst/topology-figure-1.dot a
  bit - danvet
* Remove figure numbers - danvet

Changes since v3:
* Remove rebase detritus - danvet
* Split out purely style changes into separate patches - hwentlan

Changes since v2:
* Fix commit message - checkpatch
* s/)-1/) - 1/g - checkpatch

Changes since v1:
* Remove forward declarations - danvet
* Move "Branch device and port refcounting" section from documentation
  into kernel-doc comments - danvet
* Export internal topology lifetime functions into their own section in
  the kernel-docs - danvet
* s/@/&/g for struct references in kernel-docs - danvet
* Drop the "when they are no longer being used" bits from the kernel
  docs - danvet
* Modify diagrams to show how the DRM driver interacts with the topology
  and payloads - danvet
* Make suggested documentation changes for
  drm_dp_mst_topology_get_mstb() and drm_dp_mst_topology_get_port() -
  danvet
* Better explain the relationship between malloc refs and topology krefs
  in the documentation for drm_dp_mst_topology_get_port() and
  drm_dp_mst_topology_get_mstb() - danvet
* Fix "See also" in drm_dp_mst_topology_get_mstb() - danvet
* Rename drm_dp_mst_topology_get_(port|mstb)() ->
  drm_dp_mst_topology_try_get_(port|mstb)() and
  drm_dp_mst_topology_ref_(port|mstb)() ->
  drm_dp_mst_topology_get_(port|mstb)() - danvet
* s/should/must in docs - danvet
* WARN_ON(refcount == 0) in topology_get_(mstb|port) - danvet
* Move kdocs for mstb/port structs inline - danvet
* Split drm_dp_get_last_connected_port_and_mstb() changes into their own
  commit - danvet

Signed-off-by: default avatarLyude Paul <lyude@redhat.com>
Reviewed-by: default avatarHarry Wentland <harry.wentland@amd.com>
Reviewed-by: default avatarDaniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@redhat.com>
Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Juston Li <juston.li@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-7-lyude@redhat.com
      ebcc0e6b
  37. Jan 08, 2019
  39. Dec 14, 2018
  41. Dec 05, 2018
  43. Nov 29, 2018
  45. Nov 28, 2018
  47. Nov 27, 2018
  49. Nov 24, 2018
  51. Nov 20, 2018
  53. Nov 07, 2018
  55. Nov 05, 2018
  57. Oct 24, 2018