dtoverlay: Add overlay_map functionality

The overlay_map DTB file provides a way to load different .dtbo
files on different platforms from the same overlay name, e.g.
translating "vc4-kms-v3d" to "vc4-kms-v3d-pi4" on bcm2711.

See: https://github.com/raspberrypi/linux/issues/3520

helpers/dtoverlay/dtoverlay.c

@@ -70,6 +70,9 @@ static void dtoverlay_stdio_logging(dtoverlay_logging_type_t type,
 
 static DTOVERLAY_LOGGING_FUNC *dtoverlay_logging_func = dtoverlay_stdio_logging;
 static int dtoverlay_debug_enabled = 0;
+static DTBLOB_T *overlay_map;
+static const char *platform_name;
+static int platform_name_len;
 
 static int strmemcmp(const char *mem, int mem_len, const char *str)
 {
@@ -541,8 +544,8 @@ static int dtoverlay_merge_fragment(DTBLOB_T *base_dtb, int target_off,
 
    if (dtoverlay_debug_enabled)
    {
-      char base_path[256];
-      char overlay_path[256];
+      char base_path[DTOVERLAY_MAX_PATH];
+      char overlay_path[DTOVERLAY_MAX_PATH];
       fdt_get_path(base_dtb->fdt, target_off, base_path, sizeof(base_path));
       fdt_get_path(overlay_dtb->fdt, overlay_off, overlay_path,
                    sizeof(overlay_path));
@@ -866,7 +869,7 @@ static int dtoverlay_resolve_fixups(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
 
          if (symbols_off < 0)
          {
-            dtoverlay_error("No symbols found");
+            dtoverlay_error("no symbols found");
             return -FDT_ERR_NOTFOUND;
          }
       }
@@ -1120,7 +1123,7 @@ int dtoverlay_merge_overlay(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
 
          fdt_for_each_property_offset(sym_off, overlay_dtb->fdt, frag_off)
          {
-            char target_path[256];
+            char target_path[DTOVERLAY_MAX_PATH];
             const char *sym_name = NULL;
             const char *sym_path;
             const char *p;
@@ -1180,7 +1183,7 @@ int dtoverlay_merge_overlay(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
             new_path_len = target_path_len + (sym_path + sym_len - p);
             if (new_path_len >= sizeof(target_path))
             {
-               dtoverlay_error("Exported symbol path too long for %s", sym_path);
+               dtoverlay_error("exported symbol path too long for %s", sym_path);
                err = -FDT_ERR_NOSPACE;
                break;
             }
@@ -1189,7 +1192,7 @@ int dtoverlay_merge_overlay(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
             base_symbols = fdt_path_offset(base_dtb->fdt, "/__symbols__");
             fdt_setprop(base_dtb->fdt, base_symbols,
                         sym_name, target_path, new_path_len);
-            dtoverlay_debug("Set label '%s' path to '%s'",
+            dtoverlay_debug("set label '%s' path to '%s'",
                             sym_name, target_path);
          }
          continue;
@@ -1310,7 +1313,6 @@ int dtoverlay_filter_symbols(DTBLOB_T *dtb)
    int symbols_off;
    int exports_off;
    struct str_item *exports = NULL;
-   const fdt32_t *prop_val;
    int prop_off;
 
    struct str_item
@@ -1368,7 +1370,7 @@ int dtoverlay_filter_symbols(DTBLOB_T *dtb)
       const char *name = NULL;
       struct str_item *str;
 
-      prop_val = fdt_getprop_by_offset(dtb->fdt, prop_off, &name, NULL);
+      (void)fdt_getprop_by_offset(dtb->fdt, prop_off, &name, NULL);
       if (!name)
          break;
 
@@ -1419,7 +1421,7 @@ const char *dtoverlay_find_override(DTBLOB_T *dtb, const char *override_name,
    data = fdt_getprop(dtb->fdt, overrides_off, override_name, &len);
    *data_len = len;
    if (data)
-      dtoverlay_debug("Found override %s", override_name);
+      dtoverlay_debug("found override %s", override_name);
    else
       dtoverlay_debug("/__overrides__ has no %s property", override_name);
 
@@ -2357,10 +2359,151 @@ DTBLOB_T *dtoverlay_load_dtb(const char *filename, int max_size)
    FILE *fp = fopen(filename, "rb");
    if (fp)
       return dtoverlay_load_dtb_from_fp(fp, max_size);
-   dtoverlay_error("Failed to open '%s'", filename);
+   dtoverlay_error("failed to open '%s'", filename);
    return NULL;
 }
 
+void dtoverlay_init_map_from_fp(FILE *fp, const char *compatible,
+                                int compatible_len)
+{
+    if (!compatible)
+        return;
+
+    while (compatible_len > 0)
+    {
+        const char *p;
+        int len;
+
+        // Look for a string containing a comma
+        p = memchr(compatible, ',', compatible_len);
+
+        if (p)
+        {
+            p++;
+            len = compatible + compatible_len - p;
+        }
+        else
+        {
+            // Otherwise treat it as a simple string
+            p = compatible;
+            len = compatible_len;
+        }
+
+        /* Group the members of the BCM2835 family */
+        if (strncmp(p, "bcm2708", len) == 0 ||
+            strncmp(p, "bcm2709", len) == 0 ||
+            strncmp(p, "bcm2710", len) == 0 ||
+            strncmp(p, "bcm2835", len) == 0 ||
+            strncmp(p, "bcm2836", len) == 0 ||
+            strncmp(p, "bcm2837", len) == 0)
+        {
+            platform_name = "bcm2835";
+            break;
+        }
+        else if (strncmp(p, "bcm2711", len) == 0)
+        {
+            platform_name = "bcm2711";
+            break;
+        }
+
+        compatible_len -= (p - compatible);
+        compatible = p;
+
+        len = strnlen(compatible, compatible_len) + 1;
+        compatible += len;
+        compatible_len -= len;
+    }
+
+    if (platform_name)
+    {
+        dtoverlay_debug("using platform '%s'", platform_name);
+        platform_name_len = strlen(platform_name);
+        if (fp)
+            overlay_map = dtoverlay_load_dtb_from_fp(fp, 0);
+    }
+    else
+    {
+        dtoverlay_warn("no matching platform found");
+    }
+
+    dtoverlay_debug("overlay map %sloaded", overlay_map ? "" : "not ");
+}
+
+void dtoverlay_init_map(const char *overlay_dir, const char *compatible,
+                        int compatible_len)
+{
+    char map_file[DTOVERLAY_MAX_PATH];
+    int dir_len = strlen(overlay_dir);
+    FILE *fp;
+    static int tried;
+
+    if (tried)
+        return;
+
+    tried = 1;
+
+    if (!compatible)
+        return;
+
+    /* Handle the possibility that the supplied directory may or may not end
+       with a slash */
+    sprintf(map_file, "%s%soverlay_map.dtb", overlay_dir,
+            (!dir_len || overlay_dir[dir_len - 1] != '/') ? "/" : "");
+    fp = fopen(map_file, "rb");
+    dtoverlay_init_map_from_fp(fp, compatible, compatible_len);
+}
+
+const char *dtoverlay_remap_overlay(const char *overlay)
+{
+    while (overlay_map)
+    {
+        const char *deprecated_msg;
+        const char *new_name;
+        int root_off;
+        int overlay_off;
+        int prop_len;
+
+        root_off = fdt_path_offset(overlay_map->fdt, "/");
+
+        overlay_off = fdt_subnode_offset(overlay_map->fdt, root_off, overlay);
+        if (overlay_off < 0)
+            break;
+
+        new_name = fdt_getprop_namelen(overlay_map->fdt, overlay_off,
+                                       platform_name, platform_name_len,
+                                       &prop_len);
+
+        if (new_name)
+        {
+            if (new_name[0])
+                overlay = new_name;
+            break;
+        }
+
+        // Has it been renamed or deprecated?
+        new_name = fdt_getprop_namelen(overlay_map->fdt, overlay_off,
+                                       "renamed", 7, &prop_len);
+        if (new_name)
+        {
+            dtoverlay_warn("overlay '%s' has been renamed '%s'",
+                            overlay, new_name);
+            overlay = new_name;
+            continue;
+        }
+
+        deprecated_msg = fdt_getprop_namelen(overlay_map->fdt, overlay_off,
+                                                 "deprecated", 10, &prop_len);
+        if (deprecated_msg)
+            dtoverlay_error("overlay '%s' is deprecated: %s",
+                            overlay, deprecated_msg);
+        else
+            dtoverlay_error("overlay '%s' is not supported on the '%s' platform", overlay, platform_name);
+        return NULL;
+    }
+
+    return overlay;
+}
+
 DTBLOB_T *dtoverlay_import_fdt(void *fdt, int buf_size)
 {
    DTBLOB_T *dtb = NULL;
@@ -2435,12 +2578,12 @@ int dtoverlay_save_dtb(const DTBLOB_T *dtb, const char *filename)
          goto error_exit;
       }
 
-      dtoverlay_debug("Wrote %ld bytes to '%s'", len, filename);
+      dtoverlay_debug("wrote %ld bytes to '%s'", len, filename);
       fclose(fp);
    }
    else
    {
-      dtoverlay_debug("Failed to create '%s'", filename);
+      dtoverlay_debug("failed to create '%s'", filename);
       err = -1;
    }
 
@@ -2529,7 +2672,7 @@ int dtoverlay_find_symbol(DTBLOB_T *dtb, const char *symbol_name)
 
       if (symbols_off < 0)
       {
-         dtoverlay_error("No symbols found");
+         dtoverlay_error("no symbols found");
          return -FDT_ERR_NOTFOUND;
       }
 
@@ -2595,7 +2738,7 @@ int dtoverlay_set_property(DTBLOB_T *dtb, int pos,
 {
    int err = fdt_setprop(dtb->fdt, pos, prop_name, prop, prop_len);
    if (err < 0)
-      dtoverlay_error("Failed to set property '%s'", prop_name);
+      dtoverlay_error("failed to set property '%s'", prop_name);
    return err;
 }
 
@@ -2642,6 +2785,14 @@ void dtoverlay_error(const char *fmt, ...)
    va_end(args);
 }
 
+void dtoverlay_warn(const char *fmt, ...)
+{
+   va_list args;
+   va_start(args, fmt);
+   (*dtoverlay_logging_func)(DTOVERLAY_WARN, fmt, args);
+   va_end(args);
+}
+
 void dtoverlay_debug(const char *fmt, ...)
 {
    va_list args;
@@ -2664,6 +2815,10 @@ static void dtoverlay_stdio_logging(dtoverlay_logging_type_t type,
       type_str = "error";
       break;
 
+   case DTOVERLAY_WARN:
+      type_str = "warn";
+      break;
+
    case DTOVERLAY_DEBUG:
       type_str = "debug";
       break;

helpers/dtoverlay/dtoverlay.h

@@ -45,11 +45,13 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define ONLY_FATAL(err) (IS_FATAL(err) ? (err) : 0)
 
 #define DTOVERLAY_PADDING(size) (-(size))
+#define DTOVERLAY_MAX_PATH 256
 
 typedef enum
 {
    DTOVERLAY_ERROR,
-   DTOVERLAY_DEBUG
+   DTOVERLAY_DEBUG,
+   DTOVERLAY_WARN, // Append to preserve backwards compatibility
 } dtoverlay_logging_type_t;
 
 typedef struct dtoverlay_struct
@@ -160,6 +162,13 @@ DTBLOB_T *dtoverlay_load_dtb_from_fp(FILE *fp, int max_size);
 
 DTBLOB_T *dtoverlay_load_dtb(const char *filename, int max_size);
 
+void dtoverlay_init_map_from_fp(FILE *fp, const char *compatible,
+                                int compatible_len);
+void dtoverlay_init_map(const char *overlay_dir, const char *compatible,
+                        int compatible_len);
+
+const char *dtoverlay_remap_overlay(const char *overlay);
+
 DTBLOB_T *dtoverlay_import_fdt(void *fdt, int max_size);
 
 int dtoverlay_save_dtb(const DTBLOB_T *dtb, const char *filename);
@@ -221,6 +230,8 @@ void dtoverlay_enable_debug(int enable);
 
 void dtoverlay_error(const char *fmt, ...);
 
+void dtoverlay_warn(const char *fmt, ...);
+
 void dtoverlay_debug(const char *fmt, ...);
 
 #endif

host_applications/linux/apps/dtmerge/dtmerge.c

@@ -49,11 +49,15 @@ int main(int argc, char **argv)
    const char *base_file;
    const char *merged_file;
    const char *overlay_file;
+   const char *compatible;
+   char *overlay_dir;
+   char *p;
    DTBLOB_T *base_dtb;
    DTBLOB_T *overlay_dtb;
    int err;
    int argn = 1;
    int max_dtb_size = 100000;
+   int compatible_len;
 
    while ((argn < argc) && (argv[argn][0] == '-'))
    {
@@ -87,6 +91,24 @@ int main(int argc, char **argv)
        return -1;
    }
 
+   if (strnlen(overlay_file, DTOVERLAY_MAX_PATH) == DTOVERLAY_MAX_PATH)
+   {
+       printf("* overlay filename too long\n");
+       return -1;
+   }
+
+   overlay_dir = strdup(overlay_file);
+   p = strrchr(overlay_dir, '/');
+   if (p)
+       *p = 0;
+   else
+       overlay_dir = ".";
+
+   compatible = dtoverlay_get_property(base_dtb,
+                                       dtoverlay_find_node(base_dtb, "/", 1),
+                                       "compatible", &compatible_len);
+   dtoverlay_init_map(overlay_dir, compatible, compatible_len);
+
    err = dtoverlay_set_synonym(base_dtb, "i2c", "i2c0");
    err = dtoverlay_set_synonym(base_dtb, "i2c_arm", "i2c0");
    err = dtoverlay_set_synonym(base_dtb, "i2c_vc", "i2c1");
@@ -100,11 +122,42 @@ int main(int argc, char **argv)
    }
    else
    {
-      overlay_dtb = dtoverlay_load_dtb(overlay_file, max_dtb_size);
-      if (overlay_dtb)
-          err = dtoverlay_fixup_overlay(base_dtb, overlay_dtb);
+      char new_file[DTOVERLAY_MAX_PATH];
+      char *overlay_name;
+      const char *new_name;
+      char *p;
+      int len;
+
+      strcpy(new_file, overlay_file);
+      overlay_name = strrchr(new_file, '/');
+      if (overlay_name)
+         overlay_name++;
       else
-          err = -1;
+         overlay_name = new_file;
+      p = strrchr(overlay_name, '.');
+      if (p)
+         *p = 0;
+      new_name = dtoverlay_remap_overlay(overlay_name);
+      if (new_name)
+      {
+         if (strcmp(overlay_name, new_name))
+            dtoverlay_debug("mapped overlay '%s' to '%s'", overlay_name, new_name);
+
+         len = strlen(new_name);
+         memmove(overlay_name, new_name, len);
+         strcpy(overlay_name + len, ".dtbo");
+
+         overlay_dtb = dtoverlay_load_dtb(new_file, max_dtb_size);
+         if (overlay_dtb)
+            err = dtoverlay_fixup_overlay(base_dtb, overlay_dtb);
+         else
+            err = -1;
+      }
+      else
+      {
+         overlay_dtb = NULL;
+         err = -2;
+      }
    }
 
    while (!err && (argn < argc))
@@ -165,8 +218,5 @@ int main(int argc, char **argv)
 
    dtoverlay_free_dtb(base_dtb);
 
-   if (err != 0)
-      printf("* Exiting with error code %d\n", err);
-
    return err;
 }

host_applications/linux/apps/dtoverlay/dtoverlay_main.c

@@ -102,6 +102,8 @@ const char *work_dir = WORK_DIR;
 const char *overlay_src_dir;
 const char *dt_overlays_dir;
 const char *error_file = NULL;
+const char *platform_string;
+int platform_string_len;
 int dry_run = 0;
 
 int main(int argc, const char **argv)
@@ -163,6 +165,13 @@ int main(int argc, const char **argv)
                 usage();
             overlay_src_dir = argv[argn++];
         }
+        else if (strcmp(arg, "-p") == 0)
+        {
+            if (argn == argc)
+                usage();
+            platform_string = argv[argn++];
+            platform_string_len = strlen(platform_string) + 1;
+        }
         else if (strcmp(arg, "-v") == 0)
         {
             opt_verbose = 1;
@@ -257,6 +266,34 @@ int main(int argc, const char **argv)
             fatal_error("Failed to mount configfs - %d", errno);
     }
 
+    if (!platform_string)
+    {
+        FILE *fp = fopen("/proc/device-tree/compatible", "r");
+        if (fp)
+        {
+            long len;
+            long bytes_read;
+            char *prop_buf;
+
+            fseek(fp, 0, SEEK_END);
+            len = ftell(fp);
+            fseek(fp, 0, SEEK_SET);
+            prop_buf = malloc(len);
+            bytes_read = fread(prop_buf, 1, len, fp);
+            if (bytes_read == len)
+            {
+                platform_string = prop_buf;
+                platform_string_len = len;
+            }
+            else
+                fatal_error("Failed to read 'compatible' property");
+            fclose(fp);
+        }
+    }
+
+    if (platform_string)
+        dtoverlay_init_map(overlay_src_dir, platform_string, platform_string_len);
+
     if (!dry_run)
     {
         dt_overlays_dir = sprintf_dup("%s/%s", cfg_dir, DT_OVERLAYS_SUBDIR);
@@ -425,6 +462,12 @@ static int dtoverlay_add(STATE_T *state, const char *overlay,
     }
     else
     {
+        const char *remapped = dtoverlay_remap_overlay(overlay);
+        if (!remapped)
+            return error("Failed to load '%s'", overlay);
+        if (strcmp(overlay, remapped))
+            dtoverlay_debug("mapped overlay '%s' to '%s'", overlay, remapped);
+        overlay = remapped;
         overlay_file = sprintf_dup("%s/%s.dtbo", overlay_src_dir, overlay);
     }
 
@@ -432,6 +475,7 @@ static int dtoverlay_add(STATE_T *state, const char *overlay,
         overlay_name = "dry_run";
     else
         overlay_name = sprintf_dup("%d_%s", state->count, overlay);
+    dtoverlay_debug("loading file '%s'", overlay_file);
     overlay_dtb = dtoverlay_load_dtb(overlay_file, DTOVERLAY_PADDING(4096));
     if (!overlay_dtb)
         return error("Failed to read '%s'", overlay_file);
@@ -851,7 +895,7 @@ static void usage(void)
         printf("  %s                Display help on all parameters\n", cmd_name);
         printf("  %s <param>=<val>...\n", cmd_name);
         printf("  %*s                Add an overlay (with parameters)\n", (int)strlen(cmd_name), "");
-        printf("  %s -D [<idx>]     Dry-run (prepare overlay, but don't apply -\n",
+        printf("  %s -D             Dry-run (prepare overlay, but don't apply -\n",
                cmd_name);
         printf("  %*s                save it as dry-run.dtbo)\n", (int)strlen(cmd_name), "");
         printf("  %s -r [<idx>]     Remove an overlay (by index, or the last)\n", cmd_name);
@@ -866,7 +910,7 @@ static void usage(void)
     {
         printf("  %s <overlay> [<param>=<val>...]\n", cmd_name);
         printf("  %*s                Add an overlay (with parameters)\n", (int)strlen(cmd_name), "");
-        printf("  %s -D [<idx>]     Dry-run (prepare overlay, but don't apply -\n",
+        printf("  %s -D             Dry-run (prepare overlay, but don't apply -\n",
                cmd_name);
         printf("  %*s                save it as dry-run.dtbo)\n", (int)strlen(cmd_name), "");
         printf("  %s -r [<overlay>] Remove an overlay (by name, index or the last)\n", cmd_name);
@@ -880,9 +924,10 @@ static void usage(void)
         printf("    where <overlay> is the name of an overlay or 'dtparam' for dtparams\n");
     }
     printf("Options applicable to most variants:\n");
-    printf("    -d <dir>    Specify an alternate location for the overlays\n");
-    printf("                (defaults to /boot/overlays or /flash/overlays)\n");
-    printf("    -v          Verbose operation\n");
+    printf("    -d <dir>        Specify an alternate location for the overlays\n");
+    printf("                    (defaults to /boot/overlays or /flash/overlays)\n");
+    printf("    -p <string>     Force a compatible string for the platform\n");
+    printf("    -v              Verbose operation\n");
     printf("\n");
     printf("Adding or removing overlays and parameters requires root privileges.\n");