fw_env: add fallback to Linux's NVMEM based access

A new DT binding for describing environment data block has been added in
Linux's commit 5db1c2dbc04c ("dt-bindings: nvmem: add U-Boot environment
variables binding"). Once we get a proper Linux NVMEM driver it'll be
possible to use Linux's binary interface for user-space as documented
in the:
https://www.kernel.org/doc/html/latest/driver-api/nvmem.html

This commits makes fw_env fallback to looking for a compatible NVMEM
device in case config file isn't present. In a long term this may make
config files redundant and avoid code (info) duplication.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 31afef6f3b1780f01defecce0626fdcdb0898061..908a162202d55d189a57877d610af87f3b108da5 100644 (file)
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -1713,6 +1713,67 @@ static int check_device_config(int dev)
        return rc;
 }
 
+static int find_nvmem_device(void)
+{
+       const char *path = "/sys/bus/nvmem/devices";
+       struct dirent *dent;
+       char *nvmem = NULL;
+       char comp[256];
+       char buf[32];
+       int bytes;
+       DIR *dir;
+
+       dir = opendir(path);
+       if (!dir) {
+               return -EIO;
+       }
+
+       while (!nvmem && (dent = readdir(dir))) {
+               FILE *fp;
+
+               if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, "..")) {
+                       continue;
+               }
+
+               bytes = snprintf(comp, sizeof(comp), "%s/%s/of_node/compatible", path, dent->d_name);
+               if (bytes < 0 || bytes == sizeof(comp)) {
+                       continue;
+               }
+
+               fp = fopen(comp, "r");
+               if (!fp) {
+                       continue;
+               }
+
+               fread(buf, sizeof(buf), 1, fp);
+
+               if (!strcmp(buf, "u-boot,env")) {
+                       bytes = asprintf(&nvmem, "%s/%s/nvmem", path, dent->d_name);
+                       if (bytes < 0) {
+                               nvmem = NULL;
+                       }
+               }
+
+               fclose(fp);
+       }
+
+       closedir(dir);
+
+       if (nvmem) {
+               struct stat s;
+
+               stat(nvmem, &s);
+
+               DEVNAME(0) = nvmem;
+               DEVOFFSET(0) = 0;
+               ENVSIZE(0) = s.st_size;
+
+               return 0;
+       }
+
+       return -ENOENT;
+}
+
 static int parse_config(struct env_opts *opts)
 {
        int rc;
@@ -1723,9 +1784,12 @@ static int parse_config(struct env_opts *opts)
 #if defined(CONFIG_FILE)
        /* Fills in DEVNAME(), ENVSIZE(), DEVESIZE(). Or don't. */
        if (get_config(opts->config_file)) {
-               fprintf(stderr, "Cannot parse config file '%s': %m\n",
-                       opts->config_file);
-               return -1;
+               if (find_nvmem_device()) {
+                       fprintf(stderr, "Cannot parse config file '%s': %m\n",
+                               opts->config_file);
+                       fprintf(stderr, "Failed to find NVMEM device\n");
+                       return -1;
+               }
        }
 #else
        DEVNAME(0) = DEVICE1_NAME;