Property names are stored in a string table. When a node property is removed, the string table is not updated since other nodes may have a property with the same name.
Thus it is possible for the string table to build up a number of unused strings. Add a function to remove these. This works by building a new device tree from the old one, adding strings one by one as needed.
Signed-off-by: Simon Glass sjg@chromium.org ---
Changes in v2: - Add new patch to remove unused strings from a device tree
include/libfdt.h | 17 +++++++++++++++++ lib/libfdt/fdt_rw.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+)
diff --git a/include/libfdt.h b/include/libfdt.h index f3cbb63..60e612a 100644 --- a/include/libfdt.h +++ b/include/libfdt.h @@ -1646,6 +1646,23 @@ int fdt_del_node(void *fdt, int nodeoffset);
const char *fdt_strerror(int errval);
+/** + * fdt_remove_unused_strings() - Remove any unused strings from an FDT + * + * This creates a new device tree in @new with unused strings removed. The + * called can then use fdt_pack() to minimise the space consumed. + * + * @old: Old device tree blog + * @new: Place to put new device tree blob, which must be as large as + * @old + * @return + * 0, on success + * -FDT_ERR_BADOFFSET, corrupt device tree + * -FDT_ERR_NOSPACE, out of space, which should not happen unless there + * is something very wrong with the device tree input + */ +int fdt_remove_unused_strings(const void *old, void *new); + struct fdt_region { int offset; int size; diff --git a/lib/libfdt/fdt_rw.c b/lib/libfdt/fdt_rw.c index bec8b8a..1a358a8 100644 --- a/lib/libfdt/fdt_rw.c +++ b/lib/libfdt/fdt_rw.c @@ -449,3 +449,35 @@ int fdt_pack(void *fdt)
return 0; } + +int fdt_remove_unused_strings(const void *old, void *new) +{ + const struct fdt_property *old_prop; + struct fdt_property *new_prop; + int size = fdt_totalsize(old); + int next_offset, offset; + const char *str; + int ret; + int tag = FDT_PROP; + + /* Make a copy and remove the strings */ + memcpy(new, old, size); + fdt_set_size_dt_strings(new, 0); + + /* Add every property name back into the new string table */ + for (offset = 0; tag != FDT_END; offset = next_offset) { + tag = fdt_next_tag(old, offset, &next_offset); + if (tag != FDT_PROP) + continue; + old_prop = fdt_get_property_by_offset(old, offset, NULL); + new_prop = (struct fdt_property *)(unsigned long) + fdt_get_property_by_offset(new, offset, NULL); + str = fdt_string(old, fdt32_to_cpu(old_prop->nameoff)); + ret = _fdt_find_add_string(new, str); + if (ret < 0) + return ret; + new_prop->nameoff = cpu_to_fdt32(ret); + } + + return 0; +}