[SeaBIOS] question about usb and memory zones

[Kevin O'Connor]

On Sat, Feb 28, 2015 at 10:24:16AM +0330, Navid Movahedi wrote:
> Hi
> I'm reading the seabios source code, the usb part and found that for
> example in usb-uhci.c file, in some parts malloc_low is used and in other
> malloc_high
> Now, the question: is it important for usb endpoints or pipes to be
> allocated in low or high zone of memory? and if yes, why?

There is some documentation on the memory zones at:
  http://www.seabios.org/Memory_Model

In the uhci driver, the low memory zone is used for any allocations
that need to be read/writable to code that runs in 16bit mode
(uhci_send_pipe and uhci_poll_intr).  The high memory allocations are
for DMA structures that aren't read/written to by the CPU during
runtime.

-Kevin