Even if a platform doesn't use a device tree during its
boot process it can be useful to enable CONFIG_OF and get
an empty device tree.
Then, devices can use device tree overlays to populate this
default tree.
Signed-off-by: Franck Jullien <franck.jullien@xxxxxxxxxxxxxxxxxxx>
---
drivers/of/Kconfig | 9 +++++++++
drivers/of/Makefile | 3 +++
drivers/of/base.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
drivers/of/default.dts | 4 ++++
drivers/of/unittest.c | 33 +++++----------------------------
include/linux/of.h | 2 ++
6 files changed, 73 insertions(+), 28 deletions(-)
create mode 100644 drivers/of/default.dts
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index b3bec3a..ed60af7 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -11,6 +11,15 @@ menuconfig OF
if OF
+config OF_DEFAULT_DTB
+ bool "Load default empty Device Tree"
+ depends on OF_IRQ
+ select OF_EARLY_FLATTREE
+ select OF_RESOLVE
+ help
+ This option builds in an empty device tree.
+ If unsure, say N here, but this option is safe to enable.
+
config OF_UNITTEST
bool "Device Tree runtime unit tests"
depends on OF_IRQ
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index d7efd9d..e611dc0 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -15,4 +15,7 @@ obj-$(CONFIG_OF_RESOLVE) += resolver.o
obj-$(CONFIG_OF_OVERLAY) += overlay.o
obj-$(CONFIG_OF_NUMA) += of_numa.o
+obj-y += default.dtb.o
+targets += default.dtb default.dtb.S
+
obj-$(CONFIG_OF_UNITTEST) += unittest-data/
diff --git a/drivers/of/base.c b/drivers/of/base.c
index ebf84e3..43ebf5f 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -23,6 +23,7 @@
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_graph.h>
+#include <linux/of_fdt.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/string.h>
@@ -189,10 +190,55 @@ int __of_attach_node_sysfs(struct device_node *np)
return 0;
}
+int of_get_builtin_dtb(uint8_t *dtb_begin, uint8_t *dtb_end, struct device_node **dtb_node)
+{
+ const int size = dtb_end - dtb_begin;
+ void *dtb;
+ struct device_node *node;
+ int rc;
+
+ if (!size) {
+ pr_warn("%s: No DTB to attach\n", __func__);
+ return -ENODATA;
+ }
+
+ dtb = kmemdup(dtb_begin, size, GFP_KERNEL);
+
+ if (!dtb_begin) {
+ pr_warn("%s: Failed to allocate memory for built-in dtb\n", __func__);
+ return -ENOMEM;
+ }
+
+ of_fdt_unflatten_tree(dtb, NULL, &node);
+ if (!node) {
+ pr_warn("%s: No tree to attach\n", __func__);
+ return -ENODATA;
+ }
+
+ of_node_set_flag(node, OF_DETACHED);
+ rc = of_resolve_phandles(node);
+ if (rc) {
+ pr_err("%s: Failed to resolve phandles (rc=%i)\n", __func__, rc);
+ return -EINVAL;
+ }
+
+ *dtb_node = node;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(of_get_builtin_dtb);
+
void __init of_core_init(void)
{
struct device_node *np;
+ /*
+ * __dtb_default_begin[] and __dtb_default_end[] are magically
+ * created by cmd_dt_S_dtb in scripts/Makefile.lib
+ */
+ extern uint8_t __dtb_default_begin[];
+ extern uint8_t __dtb_default_end[];
+
/* Create the kset, and register existing nodes */
mutex_lock(&of_mutex);
of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
@@ -201,6 +247,10 @@ void __init of_core_init(void)
pr_err("devicetree: failed to register existing nodes\n");
return;
}
+
+ if (!of_root && IS_ENABLED(CONFIG_OF_DEFAULT_DTB))
+ of_get_builtin_dtb(__dtb_default_begin, __dtb_default_end, &of_root);
+
for_each_of_allnodes(np)
__of_attach_node_sysfs(np);
mutex_unlock(&of_mutex);
diff --git a/drivers/of/default.dts b/drivers/of/default.dts
new file mode 100644
index 0000000..fc387fb
--- /dev/null
+++ b/drivers/of/default.dts
@@ -0,0 +1,4 @@
+/dts-v1/;
+/ {
+
+};
diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index f34ed93..2400e78 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -895,42 +895,19 @@ static int attach_node_and_children(struct device_node *np)
*/
static int __init unittest_data_add(void)
{
- void *unittest_data;
struct device_node *unittest_data_node, *np;
+ int rc;
+
/*
* __dtb_testcases_begin[] and __dtb_testcases_end[] are magically
* created by cmd_dt_S_dtb in scripts/Makefile.lib
*/
extern uint8_t __dtb_testcases_begin[];
extern uint8_t __dtb_testcases_end[];
- const int size = __dtb_testcases_end - __dtb_testcases_begin;
- int rc;
-
- if (!size) {
- pr_warn("%s: No testcase data to attach; not running tests\n",
- __func__);
- return -ENODATA;
- }
-
- /* creating copy */
- unittest_data = kmemdup(__dtb_testcases_begin, size, GFP_KERNEL);
- if (!unittest_data) {
- pr_warn("%s: Failed to allocate memory for unittest_data; "
- "not running tests\n", __func__);
- return -ENOMEM;
- }
- of_fdt_unflatten_tree(unittest_data, NULL, &unittest_data_node);
- if (!unittest_data_node) {
- pr_warn("%s: No tree to attach; not running tests\n", __func__);
- return -ENODATA;
- }
- of_node_set_flag(unittest_data_node, OF_DETACHED);
- rc = of_resolve_phandles(unittest_data_node);
- if (rc) {
- pr_err("%s: Failed to resolve phandles (rc=%i)\n", __func__, rc);
- return -EINVAL;
- }
+ rc = of_get_builtin_dtb(__dtb_testcases_begin, __dtb_testcases_end, &unittest_data_node);
+ if (rc)
+ return rc;
if (!of_root) {
of_root = unittest_data_node;
diff --git a/include/linux/of.h b/include/linux/of.h
index 74eb28c..5cab2b5 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -406,6 +406,8 @@ const char *of_prop_next_string(struct property *prop, const char *cur);
bool of_console_check(struct device_node *dn, char *name, int index);
+int of_get_builtin_dtb(uint8_t *dtb_begin, uint8_t *dtb_end, struct device_node **dtb_node);
+
#else /* CONFIG_OF */
static inline void of_core_init(void)
--
2.5.0
--
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