RSDP scan problem

RSDP scan problem

[Magnus Christensson]

There seem to be a problem with the RSDP scan in at least a few different kernel 
versions.

In the 2.6 version I looked at we have:

----
         /*
          * Scan memory looking for the RSDP signature. First search EBDA (low
          * memory) paragraphs and then search upper memory (E0000-FFFFF).
          */
         rsdp_phys = acpi_scan_rsdp (0, 0x400);
         if (!rsdp_phys)
                 rsdp_phys = acpi_scan_rsdp (0xE0000, 0xFFFFF);
----

In a 2.4 version we have:

----
	/*
	 * Physical address is given
	 */
	/*
	 * Region 1) Search EBDA (low memory) paragraphs
	 */
	rsdp = acpi_tb_scan_memory_for_rsdp(__va(LO_RSDP_WINDOW_BASE),
					 LO_RSDP_WINDOW_SIZE);
----

Both versions claim to check the EBDA in the comments, but if I'm not mistaken 
they really check the lowest part of physical memory.

The location of the EBDA varies between BIOSes (the real mode segment part can 
be found at 40:0E).

M.



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