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cbfstool: Add comment to define stability rules for cbfstool print -k 

In CB:41119, I sort of made up a mechanism on the fly for how to make
the machine-parseable cbfstool print output extensible without breaking
backwards compatibility for older scripts. But I only explained it in
the commit message which is not very visible. This patch adds a comment
to the function that generates that output so that people who want to
change it can understand the intent.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I0d18d59e7fe407eb34710d6a583cfae667723eb7
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74347
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
This commit is contained in:
Julius Werner 2023-04-11 17:01:00 -07:00
parent 46a972022b
commit ea4d4c9c33
1 changed files with 32 additions and 0 deletions
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32
util/cbfstool/cbfs_image.c
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@ -730,6 +730,12 @@ int cbfs_add_entry(struct cbfs_image *image, struct buffer *buffer,
const char *name = header->filename; const char *name = header->filename;
/* This is so special rows in cbfstool print -k -v output stay unambiguous. */
if (name[0] == '[') {
ERROR("CBFS file name `%s` must not start with `[`\n", name);
return -1;
}
uint32_t entry_type; uint32_t entry_type;
uint32_t addr, addr_next; uint32_t addr, addr_next;
struct cbfs_file *entry, *next; struct cbfs_file *entry, *next;
@ -1497,6 +1503,32 @@ int cbfs_print_entry_info(struct cbfs_image *image, struct cbfs_file *entry,
return 0; return 0;
} }
/*
* The format of this output has been stable for many years. Since it is meant
* to be parsed by scripts, we should probably not lightly make changes to it as
* that could break older scripts expecting a different format.
*
* Until CB:41119, the `-v` flag made no difference when `-k` was selected, so
* presumably no scripts were using that combination. That's why that patch left
* the output for `-k` by itself alone to avoid breaking legacy scripts, and
* expanded `-k -v` to allow an arbitrary number of `<key>:<value>` tokens at
* the end of each row behind the legacy column output. So the new output format
* stability rules should be that `-k` will stay as it is, and `-k -v` may be
* expanded to add more `<key>:<value>` tokens to the end of a row. Scripts that
* want to parse `-k -v` output should be written to gracefully ignore any extra
* such tokens where they don't recognize the key.
*
* The `-k -v` output may also include extra rows that start with a `[`. These
* do not represent a CBFS file and can instead be used to display data that is
* associated with the CBFS as a whole and not any single file. Currently
* defined are `[FMAP REGION]\t<region name>` and
* `[METADATA HASH]\t<hash>:<algo>`. More may be defined in the future and
* scripts parsing `-k -v` output should be written to gracefully ignore any
* rows starting with `[` that they don't recognize.
*
* The format for existing `<key:value>` tokens or `[` rows should never be
* changed once they are added.
*/
static int cbfs_print_parseable_entry_info(struct cbfs_image *image, static int cbfs_print_parseable_entry_info(struct cbfs_image *image,
struct cbfs_file *entry, void *arg) struct cbfs_file *entry, void *arg)
{ {