Memory Pre-allocation (mem=xxx)

[David C. Chiu]

We're working on a project that requires a two megabytes block of
contiguous memory in kernel space. Although it is well documented that
memory can be reserved by using mem=xx arguments during boot time, it is
unclear (to me) as to how a driver can automatically detect the size of
the said reserved block.

At this moment I am 'cheating' by inserting a global variable to save a
copy of total_memory before it gets replaced by __max_memory in
arch/ppc/mm/init.c so that the saved total_memory (containing the real
physical memory size passed in from boot block) is available to my
driver. But I can't help but to feel there has to be a better way to
determine the reserved buffer size. Is there something else that will do
this without having to modify the kernel?

Any comment is appreciated.

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