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

On Mon, Aug 31, 2026 at 12:39:37PM +0100, David Laight wrote:
> On Mon, 31 Aug 2026 12:13:08 +0200
> Eli Billauer <[email protected]> wrote:
> 
> > 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).
>
> Would it really make sense to allocate the four buffers separately?
> And/or use vmalloc().

My understanding is that the buffers don't need to be physically
contiguous and vmalloc()ing the entire fifo->mem in one go should work.

Eli, what do you think?
 
> David

-- 
Sincerely yours,
Mike.