Callers to dma_buf_mmap expect to fput() the vma struct's vm_file
themselves on failure.  Not restoring the struct's data on failure
causes a double-decrement of the vm_file's refcount.
Signed-off-by: NJohn Sheu <sheu@google.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

All drivers which implement this need to have some sort of refcount to
allow concurrent vmap usage. Hence implement this in the dma-buf core.

To protect against concurrent calls we need a lock, which potentially
causes new funny locking inversions. But this shouldn't be a problem
for exporters with statically allocated backing storage, and more
dynamic drivers have decent issues already anyway.

Inspired by some refactoring patches from Aaron Plattner, who
implemented the same idea, but only for drm/prime drivers.

v2: Check in dma_buf_release that no dangling vmaps are left.
Suggested by Aaron Plattner. We might want to do similar checks for
attachments, but that's for another patch. Also fix up ERR_PTR return
for vmap.

v3: Check whether the passed-in vmap address matches with the cached
one for vunmap. Eventually we might want to remove that parameter -
compared to the kmap functions there's no need for the vaddr for
unmapping.  Suggested by Chris Wilson.

v4: Fix a brown-paper-bag bug spotted by Aaron Plattner.

Cc: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: NAaron Plattner <aplattner@nvidia.com>
Tested-by: NAaron Plattner <aplattner@nvidia.com>
Reviewed-by: NRob Clark <rob@ti.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

Remove redundant 'error' variable.
Signed-off-by: NBorislav Petkov <bp@alien8.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

We never really clarified if unmap could be done in atomic context.
But since mapping might require sleeping, this implies mutex in use
to synchronize mapping/unmapping, so unmap could sleep as well.  Add
a might_sleep() to clarify this.
Signed-off-by: NRob Clark <rob@ti.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

simplifies a bunch of callers...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Fix kernel-doc warnings in drivers/base/dma*.c:

Warning(drivers/base/dma-buf.c:498): No description found for parameter 'vaddr'
Warning(drivers/base/dma-coherent.c:199): No description found for parameter 'ret'
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Some minor inline documentation fixes for gaps resulting from new patches.
Signed-off-by: NSumit Semwal <sumit.semwal@ti.com>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

The main requirement I have for this interface is for scanning out
using the USB gpu devices. Since these devices have to read the
framebuffer on updates and linearly compress it, using kmaps
is a major overhead for every update.

v2: fix warn issues pointed out by Sylwester Nawrocki.

v3: fix compile !CONFIG_DMA_SHARED_BUFFER and add _GPL for now
Signed-off-by: NDave Airlie <airlied@redhat.com>
Reviewed-by: NRob Clark <rob.clark@linaro.org>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

Compared to Rob Clark's RFC I've ditched the prepare/finish hooks
and corresponding ioctls on the dma_buf file. The major reason for
that is that many people seem to be under the impression that this is
also for synchronization with outstanding asynchronous processsing.
I'm pretty massively opposed to this because:

- It boils down reinventing a new rather general-purpose userspace
  synchronization interface. If we look at things like futexes, this
  is hard to get right.
- Furthermore a lot of kernel code has to interact with this
  synchronization primitive. This smells a look like the dri1 hw_lock,
  a horror show I prefer not to reinvent.
- Even more fun is that multiple different subsystems would interact
  here, so we have plenty of opportunities to create funny deadlock
  scenarios.

I think synchronization is a wholesale different problem from data
sharing and should be tackled as an orthogonal problem.

Now we could demand that prepare/finish may only ensure cache
coherency (as Rob intended), but that runs up into the next problem:
We not only need mmap support to facilitate sw-only processing nodes
in a pipeline (without jumping through hoops by importing the dma_buf
into some sw-access only importer), which allows for a nicer
ION->dma-buf upgrade path for existing Android userspace. We also need
mmap support for existing importing subsystems to support existing
userspace libraries. And a loot of these subsystems are expected to
export coherent userspace mappings.

So prepare/finish can only ever be optional and the exporter /needs/
to support coherent mappings. Given that mmap access is always
somewhat fallback-y in nature I've decided to drop this optimization,
instead of just making it optional. If we demonstrate a clear need for
this, supported by benchmark results, we can always add it in again
later as an optional extension.

Other differences compared to Rob's RFC is the above mentioned support
for mapping a dma-buf through facilities provided by the importer.
Which results in mmap support no longer being optional.

Note that this dma-buf mmap patch does _not_ support every possible
insanity an existing subsystem could pull of with mmap: Because it
does not allow to intercept pagefaults and shoot down ptes importing
subsystems can't add some magic of their own at these points (e.g. to
automatically synchronize with outstanding rendering or set up some
special resources). I've done a cursory read through a few mmap
implementions of various subsytems and I'm hopeful that we can avoid
this (and the complexity it'd bring with it).

Additonally I've extended the documentation a bit to explain the hows
and whys of this mmap extension.

In case we ever want to add support for explicitly cache maneged
userspace mmap with a prepare/finish ioctl pair, we could specify that
userspace needs to mmap a different part of the dma_buf, e.g. the
range starting at dma_buf->size up to dma_buf->size*2. This works
because the size of a dma_buf is invariant over it's lifetime. The
exporter would obviously need to fall back to coherent mappings for
both ranges if a legacy clients maps the coherent range and the
architecture cannot suppor conflicting caching policies. Also, this
would obviously be optional and userspace needs to be able to fall
back to coherent mappings.

v2:
- Spelling fixes from Rob Clark.
- Compile fix for !DMA_BUF from Rob Clark.
- Extend commit message to explain how explicitly cache managed mmap
  support could be added later.
- Extend the documentation with implementations notes for exporters
  that need to manually fake coherency.

v3:
- dma_buf pointer initialization goof-up noticed by Rebecca Schultz
  Zavin.

Cc: Rob Clark <rob.clark@linaro.org>
Cc: Rebecca Schultz Zavin <rebecca@android.com>
Acked-by: NRob Clark <rob.clark@linaro.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

Fix kernel-doc warnings in dma-buf.c:

Warning(drivers/base/dma-buf.c:305): No description found for parameter 'dmabuf'
Warning(drivers/base/dma-buf.c:305): Excess function parameter 'dma_buf' description in 'dma_buf_begin_cpu_access'
Warning(drivers/base/dma-buf.c:332): No description found for parameter 'dmabuf'
Warning(drivers/base/dma-buf.c:332): Excess function parameter 'dma_buf' description in 'dma_buf_end_cpu_access'
Warning(drivers/base/dma-buf.c:350): No description found for parameter 'dmabuf'
Warning(drivers/base/dma-buf.c:350): Excess function parameter 'dma_buf' description in 'dma_buf_kmap_atomic'
Warning(drivers/base/dma-buf.c:367): No description found for parameter 'dmabuf'
Warning(drivers/base/dma-buf.c:367): Excess function parameter 'dma_buf' description in 'dma_buf_kunmap_atomic'
Warning(drivers/base/dma-buf.c:385): No description found for parameter 'dmabuf'
Warning(drivers/base/dma-buf.c:385): Excess function parameter 'dma_buf' description in 'dma_buf_kmap'
Warning(drivers/base/dma-buf.c:402): No description found for parameter 'dmabuf'
Warning(drivers/base/dma-buf.c:402): Excess function parameter 'dma_buf' description in 'dma_buf_kunmap'
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Big differences to other contenders in the field (like ion) is
that this also supports highmem, so we have to split up the cpu
access from the kernel side into a prepare and a kmap step.

Prepare is allowed to fail and should do everything required so that
the kmap calls can succeed (like swapin/backing storage allocation,
flushing, ...).

More in-depth explanations will follow in the follow-up documentation
patch.

Changes in v2:

- Clear up begin_cpu_access confusion noticed by Sumit Semwal.
- Don't automatically fallback from the _atomic variants to the
  non-atomic variants. The _atomic callbacks are not allowed to
  sleep, so we want exporters to make this decision explicit. The
  function signatures are explicit, so simpler exporters can still
  use the same function for both.
- Make the unmap functions optional. Simpler exporters with permanent
  mappings don't need to do anything at unmap time.

Changes in v3:

- Adjust the WARN_ON checks for the new ->ops functions as suggested
  by Rob Clark and Sumit Semwal.
- Rebased on top of latest dma-buf-next git.

Changes in v4:

- Fixup a missing - in a return -EINVAL; statement.
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NRob Clark <rob@ti.com>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

The mutex protects the attachment list and hence needs to be held
around the callbakc to the exporters (optional) attach/detach
functions.

Holding the mutex around the map/unmap calls doesn't protect any
dma_buf state. Exporters need to properly protect any of their own
state anyway (to protect against calls from their own interfaces).
So this only makes the locking messier (and lockdep easier to anger).

Therefore let's just drop this.

v2: Rebased on top of latest dma-buf-next git.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NRob Clark <rob.clark@linaro.org>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

We need to pass the flags into dma_buf_fd at this point,
so the flags end up doing the right thing for O_CLOEXEC.
Signed-off-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NRob Clark <rob@ti.com>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

Some exporters may use DMA map/unmap APIs in dma-buf ops, which require
enum dma_data_direction for both map and unmap operations.

Thus, the unmap dma_buf_op also needs to have enum dma_data_direction as
a parameter.
Reported-by: NTomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: NSumit Semwal <sumit.semwal@ti.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

Some fields can be set without mutex protection. Initialize them before
locking the mutex.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

Remove an error label in dma_buf_attach() that just returns an error
code.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

ops, ops->map_dma_buf and ops->unmap_dma_buf are guaranteed to be
non-NULL by a check in dma_buf_export(). Remove NULL checks on those
variables in the other API functions.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

This allows drivers to make the dma buf operations structure constant.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>

This is the first step in defining a dma buffer sharing mechanism.

A new buffer object dma_buf is added, with operations and API to allow easy
sharing of this buffer object across devices.

The framework allows:
- creation of a buffer object, its association with a file pointer, and
   associated allocator-defined operations on that buffer. This operation is
   called the 'export' operation.
- different devices to 'attach' themselves to this exported buffer object, to
  facilitate backing storage negotiation, using dma_buf_attach() API.
- the exported buffer object to be shared with the other entity by asking for
   its 'file-descriptor (fd)', and sharing the fd across.
- a received fd to get the buffer object back, where it can be accessed using
   the associated exporter-defined operations.
- the exporter and user to share the scatterlist associated with this buffer
   object using map_dma_buf and unmap_dma_buf operations.

Atleast one 'attach()' call is required to be made prior to calling the
map_dma_buf() operation.

Couple of building blocks in map_dma_buf() are added to ease introduction
of sync'ing across exporter and users, and late allocation by the exporter.

For this first version, this framework will work with certain conditions:
- *ONLY* exporter will be allowed to mmap to userspace (outside of this
   framework - mmap is not a buffer object operation),
- currently, *ONLY* users that do not need CPU access to the buffer are
   allowed.

More details are there in the documentation patch.

This is based on design suggestions from many people at the mini-summits[1],
most notably from Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
Daniel Vetter <daniel@ffwll.ch>.

The implementation is inspired from proof-of-concept patch-set from
Tomasz Stanislawski <t.stanislaws@samsung.com>, who demonstrated buffer sharing
between two v4l2 devices. [2]

[1]: https://wiki.linaro.org/OfficeofCTO/MemoryManagement
[2]: http://lwn.net/Articles/454389Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: NSumit Semwal <sumit.semwal@ti.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NDave Airlie <airlied@redhat.com>
Reviewed-and-Tested-by: NRob Clark <rob.clark@linaro.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>