When finding compatible bootloader spec files, barebox will unflatten
each DTB in turn, allocating objects for each property and node, only to
compare a single property and then free all the allocations again.
Given that this operation is repeated for every device tree until a
match is found, it's a good idea to be able to compare machine
(top-level) compatibles without having to unflatten the whole FDT.
Implemnt fdt_machine_is_compatible() that does just that. This
intentionally opencodes the device tree iteration as to minimize
code and runtime size. Using libfdt without LTO would be slower
and bigger.
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
drivers/of/fdt.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++
include/of.h | 3 ++
2 files changed, 98 insertions(+)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 676b8a5535bf..aa3d2e967acd 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -668,3 +668,98 @@ void fdt_print_reserve_map(const void *__fdt)
return;
}
}
+
+static int fdt_string_is_compatible(const char *haystack, int haystack_len,
+ const char *needle, int needle_len)
+{
+ const char *p;
+ int index = 0;
+
+ while (haystack_len >= needle_len) {
+ if (memcmp(needle, haystack, needle_len + 1) == 0)
+ return OF_DEVICE_COMPATIBLE_MAX_SCORE - (index << 2);
+
+ p = memchr(haystack, '\0', haystack_len);
+ if (!p)
+ return 0;
+ haystack_len -= (p - haystack) + 1;
+ haystack = p + 1;
+ index++;
+ }
+
+ return 0;
+}
+
+bool fdt_machine_is_compatible(const struct fdt_header *fdt, size_t fdt_size, const char *compat)
+{
+ uint32_t tag;
+ const struct fdt_property *fdt_prop;
+ const char *name;
+ uint32_t dt_struct;
+ const struct fdt_node_header *fnh;
+ const void *dt_strings;
+ struct fdt_header f;
+ int ret, len;
+ int expect = FDT_BEGIN_NODE;
+ int compat_len = strlen(compat);
+
+ ret = fdt_parse_header(fdt, fdt_size, &f);
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ dt_struct = f.off_dt_struct;
+ dt_strings = (const void *)fdt + f.off_dt_strings;
+
+ while (1) {
+ const __be32 *tagp = (const void *)fdt + dt_struct;
+ if (!dt_ptr_ok(fdt, tagp))
+ return false;
+
+ tag = be32_to_cpu(*tagp);
+ if (tag != FDT_NOP && tag != expect)
+ return false;
+
+ switch (tag) {
+ case FDT_BEGIN_NODE:
+ fnh = (const void *)fdt + dt_struct;
+
+ /* The root node must have an empty name */
+ if (fnh->name[0] != '\0')
+ return false;
+
+ dt_struct = dt_struct_advance(&f, dt_struct,
+ sizeof(struct fdt_node_header) + 1);
+
+ expect = FDT_PROP;
+ break;
+
+ case FDT_PROP:
+ fdt_prop = (const void *)fdt + dt_struct;
+ len = fdt32_to_cpu(fdt_prop->len);
+
+ name = dt_string(&f, dt_strings, fdt32_to_cpu(fdt_prop->nameoff));
+ if (!name)
+ return false;
+
+ if (strcmp(name, "compatible")) {
+ dt_struct = dt_struct_advance(&f, dt_struct,
+ sizeof(struct fdt_property) + len);
+ break;
+ }
+
+ return fdt_string_is_compatible(fdt_prop->data, len, compat, compat_len);
+
+ case FDT_NOP:
+ dt_struct = dt_struct_advance(&f, dt_struct, FDT_TAGSIZE);
+ break;
+
+ default:
+ return false;
+ }
+
+ if (!dt_struct)
+ return false;
+ }
+
+ return false;
+}
diff --git a/include/of.h b/include/of.h
index 3391403a347f..b00940c8532e 100644
--- a/include/of.h
+++ b/include/of.h
@@ -64,6 +64,9 @@ void of_clean_reserve_map(void);
void fdt_add_reserve_map(void *fdt);
void fdt_print_reserve_map(const void *fdt);
+bool fdt_machine_is_compatible(const struct fdt_header *fdt, size_t fdt_size, const char *compat);
+
+
struct device;
struct driver;
struct resource;
--
2.39.2
