diff options
Diffstat (limited to 'util/cbfstool/README.fmaptool')
| -rw-r--r-- | util/cbfstool/README.fmaptool | 69 |
1 files changed, 0 insertions, 69 deletions
diff --git a/util/cbfstool/README.fmaptool b/util/cbfstool/README.fmaptool deleted file mode 100644 index 86fc3b2192..0000000000 --- a/util/cbfstool/README.fmaptool +++ /dev/null @@ -1,69 +0,0 @@ -Flashmap descriptors in coreboot -================================ -Flashmap (https://code.google.com/p/flashmap) is a binary format for representing the layout of -flash chips. Since coreboot is starting to use a "partition" of this format to describe the flash -chip layout---both at runtime and when flashing a new image onto a chip---, the project needed a -reasonably expressive plaintext format for representing such sections in the source tree. Our -solution is the fmd ("flashmap descriptor") language, and the files in this directory contain a -scanner, parser, semantic analyser, and flashmap converter. Here's an informal language description: - -# <line comment> -<image name>[@<memory-mapped address>] <image size> { - <section name>[(flags)][@<offset from start of image>] [<section size>] [{ - <subsection name>[@<offset from start of parent section>] [<subsection size>] [{ - # Sections can be nested as deeply as desired - <subsubsection name>[(flags)][@...] [...] [{...}] - }] - [<subsection name>[(flags)][@...] [...] [{...}]] - # There can be many subsections at each level of nesting: they will be inserted - # sequentially, and although gaps are allowed, any provided offsets are always - # relative to the closest parent node's and must be strictly increasing with neither - # overlapping nor degenerate-size sections. - }] -} - -Note that the above example contains a few symbols that are actually metasyntax, and therefore have -neither meaning nor place in a real file. The <.*> s indicate placeholders for parameters: - - The names are strings, which are provided as single-word---no whitespace---groups of - syntactically unimportant symbols (i.e. everything except @, {, and }): they are not surrounded - by quotes or any other form of delimiter. - - The other fields are nonnegative integers, which may be given as decimal or hexadecimal; in - either case, a K, M, or G may be appended---without intermediate whitespace---as a multiplier. - - Comments consist of anything one manages to enter, provided it doesn't start a new line. -The [.*] s indicate that a portion of the file could be omitted altogether: - - Just because something is noted as optional doesn't mean it is in every case: the answer might - actually depend on which other information is---or isn't---provided. - - The "flag" specifies the attribute or type for given section. The most - important supported flag is "CBFS", which indicates the section will contain a CBFS structure. - - In particular, it is only legal to place a (CBFS) flag on a leaf section; that is, choosing - to add child sections excludes the possibility of putting a CBFS in their parent. Such - flags are only used to decide where CBFS empty file headers should be created, and do not - result in the storage of any additional metadata in the resulting FMAP section. -Additionally, it's important to note these properties of the overall file and its values: - - Other than within would-be strings and numbers, whitespace is ignored. It goes without saying - that such power comes with responsibility, which is why this sentence is here. - - Although the .*section names must be globally unique, one of them may---but is not required to--- - match the image name. - - It is a syntax error to supply a number---besides 0---that begins with the character 0, as there - is no intention of adding octals to the mix. - - The image's memory address should be present on---and only on---layouts for memory-mapped chips. - - Although it may be evident from above, all .*section offsets are relative only to the immediate - parent. There is no way to include an absolute offset (i.e. from the beginning of flash), which - means that it is "safe" to reorder the .*section s within a particular level of nesting, as long - as the change doesn't cause their positions and sizes to necessitate overlap or zero sizes. - - A .*section with omitted offset is assumed to start at as low a position as possible---with no - consideration of alignment---and one with omitted size is assumed to fill the remaining space - until the next sibling or before the end of its parent. - - It's fine to omit any .*section 's offset, size, or both, provided its position and size are - still unambiguous in the context of its *sibling* sections and its parent's *size*. In - particular, knowledge of one .*section 's children or the .*section s' common parent's siblings - will not be used for this purpose. - - Although .*section s are not required to have children, the flash chip as a whole must have at - least one. - - Though the braces after .*section s may be omitted for those that have no children, if they are - present, they must contain at least one child. - -PL people and sympathizers may wish to examine the formal abstract syntax and context-free grammar, -which are located in fmd_scanner.l and fmd_scanner.y, respectively. Those interested in the -algorithm used to infer omitted values will feel at home in fmd.c, particularly near the definition -of validate_and_complete_info(). |