linux.git/kernel/dma/contiguous.c, branch v7.1-rc2

Merge branch 'dma-contig-for-7.1-modules-prep-v4' into dma-mapping-for-next

2026-03-31T12:52:03+00:00

Signed-off-by: Marek Szyprowski

dma: contiguous: Export dev_get_cma_area()

2026-03-31T11:27:20+00:00

The CMA dma-buf heap uses the dev_get_cma_area() function to retrieve
the default contiguous area.

Now that this function is no longer inlined, and since we want to turn
the CMA heap into a module, let's export it.

Signed-off-by: Maxime Ripard 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-4-e18fda504419@kernel.org

dma: contiguous: Make dma_contiguous_default_area static

2026-03-31T11:27:20+00:00

Now that dev_get_cma_area() is no longer inline, we don't have any user
of dma_contiguous_default_area() outside of contiguous.c so we can make
it static.

Signed-off-by: Maxime Ripard 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-3-e18fda504419@kernel.org

dma: contiguous: Make dev_get_cma_area() a proper function

2026-03-31T11:27:20+00:00

As we try to enable dma-buf heaps, and the CMA one in particular, to
compile as modules, we need to export dev_get_cma_area(). It's currently
implemented as an inline function that returns either the content of
device->cma_area or dma_contiguous_default_area.

Thus, it means we need to export dma_contiguous_default_area, which
isn't really something we want any module to have access to.

Instead, let's make dev_get_cma_area() a proper function we will be able
to export so we can avoid exporting dma_contiguous_default_area.

Signed-off-by: Maxime Ripard 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-2-e18fda504419@kernel.org

dma: contiguous: Turn heap registration logic around

2026-03-31T11:27:20+00:00

The CMA heap instantiation was initially developed by having the
contiguous DMA code call into the CMA heap to create a new instance
every time a reserved memory area is probed.

Turning the CMA heap into a module would create a dependency of the
kernel on a module, which doesn't work.

Let's turn the logic around and do the opposite: store all the reserved
memory CMA regions into the contiguous DMA code, and provide an iterator
for the heap to use when it probes.

Signed-off-by: Maxime Ripard 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-1-e18fda504419@kernel.org

of: reserved_mem: replace CMA quirks by generic methods

2026-03-26T19:12:02+00:00

Add optional reserved memory callbacks to perform region verification and
early fixup, then move all CMA related code in of_reserved_mem.c to them.

Signed-off-by: Marek Szyprowski 
Link: https://patch.msgid.link/20260325090023.3175348-5-m.szyprowski@samsung.com
Signed-off-by: Rob Herring (Arm)

of: reserved_mem: switch to ops based OF_DECLARE()

2026-03-26T19:12:02+00:00

Move init function from OF_DECLARE() argument to the given reserved
memory region ops structure and then pass that structure to the
OF_DECLARE() initializer. This node_init callback is mandatory for the
reserved mem driver. Such change makes it possible in the future to add
more functions called by the generic code before given memory region is
initialized and rmem object is created.

Signed-off-by: Marek Szyprowski 
Link: https://patch.msgid.link/20260325090023.3175348-4-m.szyprowski@samsung.com
Signed-off-by: Rob Herring (Arm)

of: reserved_mem: use -ENODEV instead of -ENOENT

2026-03-26T19:12:02+00:00

When given reserved memory region doesn't really support given node,
return -ENODEV instead of -ENOENT. Then fix __reserved_mem_init_node()
function to properly propagate error code different from -ENODEV instead
of silently ignoring it.

Signed-off-by: Marek Szyprowski 
Link: https://patch.msgid.link/20260325090023.3175348-3-m.szyprowski@samsung.com
Signed-off-by: Rob Herring (Arm)

of: reserved_mem: remove fdt node from the structure

2026-03-26T19:12:02+00:00

FDT node is not needed for anything besides the initialization, so it can
be simply passed as an argument to the reserved memory region init
function.

Signed-off-by: Marek Szyprowski 
Link: https://patch.msgid.link/20260325090023.3175348-2-m.szyprowski@samsung.com
Signed-off-by: Rob Herring (Arm)

dma: contiguous: Check return value of dma_contiguous_reserve_area()

2026-02-02T08:20:32+00:00

Commit 8f1fc1bf1a3d ("dma: contiguous: Reserve default CMA heap")
introduced a bug where dma_heap_cma_register_heap() is called with
a NULL pointer when dma_contiguous_reserve_area() fails to reserve
the CMA area.

When dma_contiguous_reserve_area() fails, dma_contiguous_default_area
remains NULL (initialized as a global variable), but the code doesn't
check the return value and proceeds to call dma_heap_cma_register_heap()
with this NULL pointer.

Later during boot, add_cma_heaps() iterates through the dma_areas[]
array and attempts to register heaps. When it encounters the NULL
pointer stored by the earlier call, it crashes in __add_cma_heap()
-> dma_heap_add() when trying to dereference the NULL CMA pointer.

The crash manifests as:
  Unable to handle kernel NULL pointer dereference at virtual address
  0000000000000038
  ...
  Call trace:
   dma_heap_add+0x40/0x2b0
   __add_cma_heap+0x80/0xe0
   add_cma_heaps+0x64/0xb0
   do_one_initcall+0x60/0x318
   kernel_init_freeable+0x260/0x2f0
   kernel_init+0x2c/0x168
   ret_from_fork+0x10/0x20

Fix this by checking the return value of dma_contiguous_reserve_area()
and only calling dma_heap_cma_register_heap() when the reservation
succeeds.

Fixes: 8f1fc1bf1a3d ("dma: contiguous: Reserve default CMA heap")
Signed-off-by: Shanker Donthineni 
Reviewed-by: T.J. Mercier 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260129181317.2429196-1-sdonthineni@nvidia.com