char: xillybus: replace __get_free_pages() with kmalloc()

fifo_init() allocates the buffers backing the software FIFO and
endpoint_alloc() allocates the transfer buffers of a USB endpoint.

These buffers can be allocated with kmalloc() as there's nothing special
about them to go directly to the page allocator.

kmalloc() provides a better API that does not require ugly casts and
kfree() does not need to know the size of the freed object.

Performance difference between kmalloc() and __get_free_pages() is not
measurable as both allocators take an object/page from a per-CPU list for
fast path allocations.

For the slow path the performance is anyway determined by the amount of
reclaim involved rather than by what allocator is used.

Since kmalloc() does not need the allocation order, ask it for the buffer
sizes the driver already tracks and drop the now unused order fields. For
a FIFO smaller than a page this also stops rounding the allocation up to
PAGE_SIZE.

Replace use of __get_free_pages() with kmalloc() and free_pages() with
kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
Assisted-by: copilot:claude-opus
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260830-char-misc-v1-2-05e2ce44f291@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions