Hi all,
This patch series is based on a previous discussion around CMA heap
naming. [1] The heap's name depends on the device name, which is
generally "reserved", "linux,cma", or "default-pool", but could be any
arbitrary name given to the default CMA area in the devicetree. For a
consistent userspace interface, the series introduces a constant name
for the CMA heap, and for backwards compatibility, an additional Kconfig
that controls the creation of a legacy-named heap with the same CMA
backing.
The ideas to handle backwards compatibility in [1] are to either use a
symlink or add a heap node with a duplicate minor. However, I assume
that we don't want to create symlinks in /dev from module initcalls, and
attempting to duplicate minors would cause device_create() to fail.
Because of these drawbacks, after brainstorming with Maxime Ripard, I
went with creating a new node in devtmpfs with its own minor. This
admittedly makes it a little unclear that the old and new nodes are
backed by the same heap when both are present. The only approach that I
think would provide total clarity on this in userspace is symlinking,
which seemed like a fairly involved solution for devtmpfs, but if I'm
wrong on this, please let me know.
Changelog:
v2: Use tabs instead of spaces for large vertical alignment.
Jared Kangas (2):
dma-buf: heaps: Parameterize heap name in __add_cma_heap()
dma-buf: heaps: Give default CMA heap a fixed name
Documentation/userspace-api/dma-buf-heaps.rst | 11 ++++---
drivers/dma-buf/heaps/Kconfig | 10 +++++++
drivers/dma-buf/heaps/cma_heap.c | 30 ++++++++++++++-----
3 files changed, 40 insertions(+), 11 deletions(-)
--
2.49.0
