dtoverlay app: Add the -D (dry-run) option

Dry-run mode does the same processing as adding an overlay, but instead
of submitting the overlay to the kernel it saves the result in
"dry_run.dtbo" in the current directory. This feature is provided as a
diagnostic aid - when combined with the dtmerge command it allows one
to simulate the application of an overlay in the same manner as the
dynamic overlays are applied.

diff --git a/host_applications/linux/apps/dtoverlay/dtoverlay_main.c b/host_applications/linux/apps/dtoverlay/dtoverlay_main.c
index a02bedaf32d137436b635118173c611fdc430d3d..5f87e66b49e7416871d225b958a9508676ba62c8 100755 (executable)
--- a/host_applications/linux/apps/dtoverlay/dtoverlay_main.c
+++ b/host_applications/linux/apps/dtoverlay/dtoverlay_main.c
@@ -102,6 +102,7 @@ const char *work_dir = WORK_DIR;
 const char *overlay_src_dir;
 const char *dt_overlays_dir;
 const char *error_file = NULL;
+int dry_run = 0;
 
 int main(int argc, const char **argv)
 {
@@ -134,6 +135,13 @@ int main(int argc, const char **argv)
                 usage();
             opt = OPT_REMOVE_FROM;
         }
+        else if (strcmp(arg, "-D") == 0)
+        {
+            if (opt != OPT_ADD)
+                usage();
+            dry_run = 1;
+            work_dir = ".";
+        }
         else if ((strcmp(arg, "-l") == 0) ||
                  (strcmp(arg, "--list") == 0))
         {
@@ -232,7 +240,7 @@ int main(int argc, const char **argv)
     error_file = sprintf_dup("%s/%s", work_dir, "error.dtb");
 
     cfg_dir = CFG_DIR_1 DT_SUBDIR;
-    if (!dir_exists(cfg_dir))
+    if (!dry_run && !dir_exists(cfg_dir))
     {
        root_check();
 
@@ -253,18 +261,24 @@ int main(int argc, const char **argv)
     if (!dir_exists(dt_overlays_dir))
        fatal_error("configfs overlays folder not found - incompatible kernel");
 
-    state = read_state(work_dir);
-    if (!state)
-       fatal_error("Failed to read state");
+    if (!dry_run)
+    {
+        state = read_state(work_dir);
+        if (!state)
+            fatal_error("Failed to read state");
+    }
 
     switch (opt)
     {
     case OPT_ADD:
     case OPT_REMOVE:
     case OPT_REMOVE_FROM:
-       root_check();
-       run_cmd("which dtoverlay-pre >/dev/null 2>&1 && dtoverlay-pre");
-       break;
+        if (!dry_run)
+        {
+            root_check();
+            run_cmd("which dtoverlay-pre >/dev/null 2>&1 && dtoverlay-pre");
+        }
+        break;
     default:
        break;
     }
@@ -296,7 +310,8 @@ int main(int argc, const char **argv)
     case OPT_ADD:
     case OPT_REMOVE:
     case OPT_REMOVE_FROM:
-       run_cmd("which dtoverlay-post >/dev/null 2>&1 && dtoverlay-post");
+       if (!dry_run)
+           run_cmd("which dtoverlay-post >/dev/null 2>&1 && dtoverlay-post");
        break;
     default:
        break;
@@ -421,7 +436,10 @@ static int dtoverlay_add(STATE_T *state, const char *overlay,
        overlay_file = sprintf_dup("%s/%s.dtbo", overlay_src_dir, overlay);
     }
 
-    overlay_name = sprintf_dup("%d_%s", state->count, overlay);
+    if (dry_run)
+        overlay_name = "dry_run";
+    else
+       overlay_name = sprintf_dup("%d_%s", state->count, overlay);
     overlay_dtb = dtoverlay_load_dtb(overlay_file, DTOVERLAY_PADDING(4096));
     if (!overlay_dtb)
        return error("Failed to read '%s'", overlay_file);
@@ -514,7 +532,7 @@ static int dtoverlay_add(STATE_T *state, const char *overlay,
     dtoverlay_save_dtb(overlay_dtb, overlay_file);
     dtoverlay_free_dtb(overlay_dtb);
 
-    if (!apply_overlay(overlay_file, overlay_name))
+    if (!dry_run && !apply_overlay(overlay_file, overlay_name))
     {
        if (error_file)
        {
@@ -836,6 +854,9 @@ 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",
+          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);
     printf("  %s -R [<idx>]     Remove from an overlay (by index, or all)\n",
           cmd_name);
@@ -848,6 +869,9 @@ 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",
+          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);
     printf("  %s -R [<overlay>] Remove from an overlay (by name, index or all)\n",
           cmd_name);