The devicetree spec introduced a mechanism to match devicetree blobs to boards using firmware-provided identifiers. Although the matching can be implemented by DTB loaders, having a canonical implementation makes it easier to integrate and ensure consistent behavior across ecosystems.
I've not yet investigated swig/python support for the new functions; I would work on that before submitting the patch to libfdt.
Signed-off-by: Elliot Berman quic_eberman@quicinc.com --- scripts/dtc/libfdt/fdt_ro.c | 76 +++++++++++++++++++++++++++++++++++++++++++++ scripts/dtc/libfdt/libfdt.h | 54 ++++++++++++++++++++++++++++++++ 2 files changed, 130 insertions(+)
diff --git a/scripts/dtc/libfdt/fdt_ro.c b/scripts/dtc/libfdt/fdt_ro.c index 9f6c551a22c2..b19b17127399 100644 --- a/scripts/dtc/libfdt/fdt_ro.c +++ b/scripts/dtc/libfdt/fdt_ro.c @@ -857,3 +857,79 @@ int fdt_node_offset_by_compatible(const void *fdt, int startoffset,
return offset; /* error from fdt_next_node() */ } + +int fdt_board_id_prop_matches(const void *fdt, + const struct fdt_property *prop, + fdt_get_board_id_t get_board_id_cb, + void *ctx) +{ + int data_len; + const void *data; + const char *name; + int name_len; + int string = 0; + + name = fdt_get_string(fdt, fdt32_to_cpu(prop->nameoff), &name_len); + if (!name) + return -FDT_ERR_BADOFFSET; + + if (name_len > 4 && !strcmp(name + name_len - 4, "_str")) + string = 1; + + data = get_board_id_cb(ctx, name, &data_len); + if (!data) + return -FDT_ERR_NOTFOUND; + + if (string) { + return fdt_stringlist_contains(prop->data, + fdt32_to_cpu(prop->len), + data); + } else { + // exact data comparison. data_len is the size of each entry + if (fdt32_to_cpu(prop->len) % data_len || data_len % 4) + return -FDT_ERR_BADVALUE; + + for (int i = 0; i < fdt32_to_cpu(prop->len); i += data_len) { + if (!memcmp(&prop->data[i], data, data_len)) + return 1; + } + + return 0; + } + + return 0; +} + +int fdt_board_id_score(const void *fdt, fdt_get_board_id_t get_board_id_cb, + void *ctx) +{ + const struct fdt_property *prop; + int node, property, ret, score = 0; + const char *name; + + node = fdt_path_offset(fdt, "/board-id"); + if (node < 0) + return node; + + fdt_for_each_property_offset(property, fdt, node) { + prop = fdt_get_property_by_offset(fdt, property, NULL); + if (!prop) + return -FDT_ERR_BADOFFSET; + + name = fdt_get_string(fdt, fdt32_to_cpu(prop->nameoff), NULL); + if (!name) + return -FDT_ERR_BADOFFSET; + + if (!strcmp(name, "phandle") || !strcmp(name, "linux,phandle")) + continue; + + ret = fdt_board_id_prop_matches(fdt, prop, get_board_id_cb, + ctx); + if (ret == 1) + score++; + else + return ret; + } + + return score; +} diff --git a/scripts/dtc/libfdt/libfdt.h b/scripts/dtc/libfdt/libfdt.h index 77ccff19911e..de1cbc339315 100644 --- a/scripts/dtc/libfdt/libfdt.h +++ b/scripts/dtc/libfdt/libfdt.h @@ -1230,6 +1230,60 @@ int fdt_address_cells(const void *fdt, int nodeoffset); */ int fdt_size_cells(const void *fdt, int nodeoffset);
+/**********************************************************************/ +/* Read-only functions (board-id related) */ +/**********************************************************************/ + +/** + * fdt_get_board_id_t - callback to retrieve the board id for the platform + * @ctx: Context data passed from fdt_board_id_prop_matches() + * @name: board id name + * @data: Callback sets pointer to the board id data + * @datalen: Callback sets length of the board id data + * + * returns: + * Pointer to the board id data, NULL if the data doesn't exist + */ +typedef const void *(*fdt_get_board_id_t)(void *ctx, const char *name, + int *datalen); + +/** + * fdt_board_id_prop_matches - check if the property matches the platform's board id + * @fdt: pointer to the device tree blob + * @prop_offset: Offset of the property to match + * @get_board_id_cb: Function pointer to retrieve the platform's board id + * + * returns: + * 1: the property matches + * 0: the property doesn't match + * -FDT_ERR_BADMAGIC, + * -FDT_ERR_BADVERSION, + * -FDT_ERR_BADSTATE, + * -FDT_ERR_BADSTRUCTURE, + * -FDT_ERR_TRUNCATED, standard meanings + */ +int fdt_board_id_prop_matches(const void *fdt, + const struct fdt_property *prop, + fdt_get_board_id_t get_board_id_cb, + void *ctx); + +/** + * fdt_board_id_score - calculate score of the fdt's board_id + * @fdt: pointer to the device tree blob + * @get_board_id_cb: Function pointer to retrieve the platform's board id + * + * returns: + * >0 for the number of board-id properties that were matched + * 0 if there was a mismatch in any of the board-id properties + * -FDT_ERR_BADMAGIC, + * -FDT_ERR_BADVERSION, + * -FDT_ERR_BADSTATE, + * -FDT_ERR_BADSTRUCTURE, + * -FDT_ERR_TRUNCATED, standard meanings + */ +int fdt_board_id_score(const void *fdt, fdt_get_board_id_t get_board_id_cb, + void *ctx); +
/**********************************************************************/ /* Write-in-place functions */