[Qemu-devel] [PATCH 2/6] device_tree: introduce load_device_tree_from_sysfs

[Eric Auger]

This function returns the host device tree blob from sysfs
(/sys/firmware/devicetree/base). It uses a recursive function
inspired from dtc read_fstree.

Signed-off-by: Eric Auger <address@hidden>

---

RFC -> v1:
- remove runtime dependency on dtc binary and introduce read_fstree
---
 device_tree.c                | 102 +++++++++++++++++++++++++++++++++++++++++++
 include/sysemu/device_tree.h |   1 +
 2 files changed, 103 insertions(+)

diff --git a/device_tree.c b/device_tree.c
index a9f5f8e..e556a99 100644
--- a/device_tree.c
+++ b/device_tree.c
@@ -17,6 +17,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <dirent.h>
 
 #include "qemu-common.h"
 #include "qemu/error-report.h"
@@ -117,6 +118,107 @@ fail:
     return NULL;
 }
 
+/**
+ * read_fstree: this function is inspired from dtc read_fstree
+ * @fdt: preallocated fdt blob buffer, to be populated
+ * @dirname: directory to scan under /sys/firmware/devicetree/base
+ * the search is recursive and the tree is search down to the
+ * leafs (property files).
+ *
+ * the function self-asserts in case of error
+ */
+static void read_fstree(void *fdt, const char *dirname)
+{
+        DIR *d;
+        struct dirent *de;
+        struct stat st;
+        const char *root_dir = "/sys/firmware/devicetree/base";
+        char *parent_node;
+
+        if (strstr(dirname, root_dir) != dirname) {
+            error_report("%s: %s must be searched within %s",
+                         __func__, dirname, root_dir);
+            exit(1);
+        }
+        parent_node = (char *)&dirname[29];
+
+        d = opendir(dirname);
+        if (!d) {
+                error_report("%s cannot open %s", __func__, dirname);
+                exit(1);
+        }
+
+        while ((de = readdir(d)) != NULL) {
+                char *tmpnam;
+
+                if (!g_strcmp0(de->d_name, ".")
+                    || !g_strcmp0(de->d_name, "..")) {
+                        continue;
+                }
+
+                tmpnam = g_strjoin("/", dirname, de->d_name, NULL);
+
+                if (lstat(tmpnam, &st) < 0) {
+                        error_report("%s cannot lstat %s", __func__, tmpnam);
+                        exit(1);
+                }
+
+                if (S_ISREG(st.st_mode)) {
+                    int ret, size = st.st_size;
+                    void *val = g_malloc0(size);
+                    FILE *pfile;
+
+                    pfile = fopen(tmpnam, "r");
+                    if (!pfile) {
+                        error_report("%s cannot open %s", __func__, tmpnam);
+                        exit(1);
+                    }
+                    ret = fread(val, 1, size, pfile);
+                    if (ferror(pfile) || ret < size) {
+                        error_report("%s fail reading %s", __func__, tmpnam);
+                        exit(1);
+                    }
+                    fclose(pfile);
+
+                    if (strlen(parent_node) > 0) {
+                        qemu_fdt_setprop(fdt, parent_node,
+                                         de->d_name, val, size);
+                    } else {
+                        qemu_fdt_setprop(fdt, "/", de->d_name, val, size);
+                    }
+                    g_free(val);
+                } else if (S_ISDIR(st.st_mode)) {
+                        char *node_name;
+
+                        node_name = g_strdup_printf("%s/%s",
+                                                    parent_node, de->d_name);
+                        qemu_fdt_add_subnode(fdt, node_name);
+                        g_free(node_name);
+                        read_fstree(fdt, tmpnam);
+                }
+
+                g_free(tmpnam);
+        }
+
+        closedir(d);
+}
+
+/* load_device_tree_from_sysfs: extract the dt blob from host sysfs */
+void *load_device_tree_from_sysfs(void)
+{
+    void *host_fdt;
+    int host_fdt_size;
+
+    host_fdt = create_device_tree(&host_fdt_size);
+    read_fstree(host_fdt, "/sys/firmware/devicetree/base");
+    if (fdt_check_header(host_fdt)) {
+        error_report("%s host device tree extracted into memory is invalid",
+                     __func__);
+        g_free(host_fdt);
+    }
+    return host_fdt;
+}
+
 static int findnode_nofail(void *fdt, const char *node_path)
 {
     int offset;
diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
index 359e143..307e53d 100644
--- a/include/sysemu/device_tree.h
+++ b/include/sysemu/device_tree.h
@@ -16,6 +16,7 @@
 
 void *create_device_tree(int *sizep);
 void *load_device_tree(const char *filename_path, int *sizep);
+void *load_device_tree_from_sysfs(void);
 
 int qemu_fdt_setprop(void *fdt, const char *node_path,
                      const char *property, const void *val, int size);
-- 
1.9.1