RE: alloc_bootmem - Kernel panic

[Martyn Welch]

Hi Asgard,

Thank you for your reply.
	
> I don't sure, that linux performs to allocate bootmem after kernel already booted.
> As I know, bootmem allocator "destroyed" when kernel initializes buddy allocator.
> Indeed you can look at arch/i385/mm/init.c, mem_init routine.
> kernel passes all bootmem pages to buddy system, so bootmem allocator can't be used after it. 
	
That explains why I can't use alloc_bootmem. It'd assumed that do_initcalls and hence functions labelled with module_init() were called early enough, mainly because LDD3 suggests using alloc_bootmem. It seems the vt driver uses console_init() instead, which is called much earlier.

Which leads me to the question: what is the best method to reserve a large (~4MB) coherent buffer for DMA transfers?

Is there any way of using alloc_bootmem from a driver (compiled into the kernel) without delving further into kernel code?

Martyn

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