Hello Jared, On Wed, 23 Apr 2025 at 00:49, Jared Kangas <jkan...@redhat.com> wrote: > > 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.
Thanks indeed for this patch; just one minor nit: the link referred to as [1] here seems to be missing. Could you please add it? This would make it easier to follow the chain of discussion in posterity. > > 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 > Best, Sumit
