This adds the documentation for the extended crashkernel syntax into
Documentation/kdump/kdump.txt.

Signed-off-by: Bernhard Walle <[EMAIL PROTECTED]>

---
 Documentation/kdump/kdump.txt       |   26 ++++++++++++++++++++++++++
 Documentation/kernel-parameters.txt |    7 +++++++
 2 files changed, 33 insertions(+)

--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -231,6 +231,32 @@ Dump-capture kernel config options (Arch
   any space below the alignment point will be wasted.
 
 
+Extended crashkernel syntax
+===========================
+
+While the "[EMAIL PROTECTED]" syntax is sufficient for most
+configurations, sometimes it's handy to have the reserved memory dependent
+on the value of System RAM -- that's mostly for distributors that pre-setup
+the kernel command line to avoid a unbootable system after some memory has
+been removed from the machine.
+
+The syntax is:
+
+    crashkernel=<range1>:<size1>[,<range2>:<size2>,[EMAIL PROTECTED]
+    range=start-[end]
+
+For example:
+
+    crashkernel=512M-2G:64M,2G-:128M
+
+This would mean:
+
+    1) if the RAM is smaller than 512M, then don't reserve anything
+       (this is the "rescue" case)
+    2) if the RAM size is between 512M and 2G, then reserve 64M
+    3) if the RAM size is larger than 2G, then reserve 128M
+
+
 Boot into System Kernel
 =======================
 
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -495,6 +495,13 @@ and is between 256 and 4096 characters. 
                        [KNL] Reserve a chunk of physical memory to
                        hold a kernel to switch to with kexec on panic.
 
+       crashkernel=range1:size1[,range2:size2,[EMAIL PROTECTED]
+                       [KNL] Same as above, but depends on the memory
+                       in the running system. The syntax of range is
+                       start-[end] where start and end are both
+                       a memory unit (amount[KMG]). See also
+                       Documentation/kdump/kdump.txt for a example.
+
        cs4232=         [HW,OSS]
                        Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
 

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