Re: [PATCH 2/4] char: xillybus: replace __get_free_pages() with kmalloc()

[Eli Billauer]

On 30/08/2026 9:47, Mike Rapoport (Microsoft) wrote:
> 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.

Except that they are a bit large.

fifo_init() may be requested to allocate up to 256 MB of buffer memory. 
This memory resource is split into an array of buffers (fifo->mem[i]), 
each 64 kiB (or less, if there's trouble obtaining segments of this size).

Citing Documentation/core-api/memory-allocation.rst:

"The maximal size of a chunk that can be allocated with `kmalloc` is 
limited. The actual limit depends on the hardware and the kernel 
configuration, but it is a good practice to use `kmalloc` for objects 
smaller than page size."

Regards,
   Eli