I have made a very simple mod to cbfstool that is compatible with the

src/lib/ code in coreboot. I.e. the tool changes but the coreboot code
does not.

Currently, as cbfstool manages the ROM, there are files and empty
space. To allocate files, the code does, first, a walk of the headers
and, if that fails, does a brute-force search of the rest of the
space.

We all agree that the brute-force search has lots of problems from a
performance and correctness standpoint.

I've made a slight change. Instead of an "empty space" area with no
valid headers, I've made a header for the empty space.

So cbfs creation looks like this:
- set up the boot block
- create a file, of type CBFS_COMPONENT_NULL, that contains the empty
space. CBFS_COMPONENT_NULL was already defined in cbfs.h

Here's an example:

[rminnich@xcpu2 cbfstool]$ ./cbfstool testcbfs create 1048576 2048
(cbfstool) E: Unable to open (null): Bad address
[rminnich@xcpu2 cbfstool]$ ./cbfstool testcbfs print
testcbfs: 1024 kB, bootblocksize 2048, romsize 1048576, offset 0x0
Alignment: 16 bytes

Name                           Offset     Type         Size
                              0x0        0xffffffff   1046456

So how do we create a new file?

It's easy: walk the files and find a file of type CBFS_COMPONENT_NULL,
which is as large
or larger than the file you are trying to create. Then you use that file.
- if the file is the same size as the NULL file, then it's easy: take it
- if the file is smaller than the NULL file, you split the NULL file
into two parts.

note that this works in the base case: the base case is that the whole
storage is CBFS_COMPONENT_NULL.

Here's an example of adding a file.
[rminnich@xcpu2 cbfstool]$ ./cbfstool testcbfs add-stage testfixed t
[rminnich@xcpu2 cbfstool]$ ./cbfstool testcbfs print
testcbfs: 1024 kB, bootblocksize 2048, romsize 1048576, offset 0x0
Alignment: 16 bytes

Name                           Offset     Type         Size
t                              0x0        stage        23176
                              0x5ab0     0xffffffff   1023240

Note that the NULL split and got smaller. But the entire ROM is still
contained by the two files. To walk this entire rom will require two
FLASH accesses.

Add another file:
[rminnich@xcpu2 cbfstool]$ ./cbfstool testcbfs add-stage testfixed tt
[rminnich@xcpu2 cbfstool]$ ./cbfstool testcbfs print
testcbfs: 1024 kB, bootblocksize 2048, romsize 1048576, offset 0x0
Alignment: 16 bytes

Name                           Offset     Type         Size
t                              0x0        stage        23176
tt                             0x5ab0     stage        23176
                              0xb560     0xffffffff   1000024
[rminnich@xcpu2 cbfstool]$

So, taking current ROMs as an example, I can reduce FLASH accesses for
cbfs from (potentially) thousands to (typically) less than 10.

Index: fs.c
Changes for readability and cleanliness. Move common blobs of code to functions. 
New function: rom_alloc,which allocates files by finding NULL files and using/splitting. 
Other changes as needed to support this usage. 
Index: util.c
Creating a cbfs archive now requires creation of a NULL file covering the file system space. 
Index: cbfs.h
Add a DELETED file type with value 0. Any file can be marked deleted by zero its type; this is a 
FLASH-friendly definition for all known FLASH types. 

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>

I think it is a step in the right direction.  Could you add the
function prototype to cbfstool.h?

Acked-by: Myles Watson <mylesgw@gmail.com>
(I added the prototype)




git-svn-id: svn://svn.coreboot.org/coreboot/trunk@4261 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

1 files changed, 10 insertions, 0 deletions

diff --git a/util/cbfstool/cbfs.h b/util/cbfstool/cbfs.h
index 95159ebaa8..04a12fc24a 100644
--- a/util/cbfstool/cbfs.h
+++ b/util/cbfstool/cbfs.h
@@ -38,6 +38,16 @@
 #define CBFS_COMPONENT_PAYLOAD   0x20
 #define CBFS_COMPONENT_OPTIONROM 0x30
 
+/* The deleted type is chosen to be a value
+ * that can be written in a FLASH from all other
+ * values. 
+ */
+#define CBFS_COMPONENT_DELETED 0
+
+/* for all known FLASH, this value can be changed 
+ * to all other values. This allows NULL files to be 
+ * changed without a block erase
+ */
 #define CBFS_COMPONENT_NULL 0xFFFFFFFF
 
 /** this is the master cbfs header - it need to be