[PATCH 0/2] of: populate of_root_node if not set (alternate)

[PATCH 0/2] of: populate of_root_node if not set (alternate)

[frowand.list]

From: Frank Rowand <frank.rowand@sony.com>

This series is a different implementation to achieve the goals of
https://lore.kernel.org/r/20220623105044.152832-1-clement.leger@bootlin.com

In order to apply overlays or create new nodes under the root node, the
kernel expects of_root to be set. On some system where a device-tree was
not provided by firmware (x86 for instance) if CONFIG_OF is enabled,
then we will end up with a null of_root. This series add support to
create this root node using a builtin dtb and remove the manual
creation of the root node done in unittests.c.

This series modifies init/main.c.  It was not clear to me whether
to add Linus to the distribution, or if the change should flow
through Rob.  (I did not add Linus.)

Frank Rowand (2):
  of: create of_root if no dtb provided
  of: unittest: treat missing of_root as error instead of fixing up

 drivers/of/Makefile    |  2 +-
 drivers/of/fdt.c       | 19 ++++++++++++++++++-
 drivers/of/unittest.c  | 16 ++++++----------
 include/linux/of_fdt.h |  2 ++
 init/main.c            |  2 ++
 5 files changed, 29 insertions(+), 12 deletions(-)

-- 
Frank Rowand <frank.rowand@sony.com>

[PATCH 0/2] of: populate of_root_node if not set (alternate)

[Frank Rowand]

This series is a different implementation to achieve the goals of
https://lore.kernel.org/r/20220623105044.152832-1-clement.leger@bootlin.com

In order to apply overlays or create new nodes under the root node, the
kernel expects of_root to be set. On some system where a device-tree was
not provided by firmware (x86 for instance) if CONFIG_OF is enabled,
then we will end up with a null of_root. This series adds support to
create this root node using a builtin dtb and removes the manual
creation of the root node done in unittests.c.

Changes since version 1: (patch 1/2)
  - refresh for 6.2-rc1
  - update Signed-off-by
  - fix typo in of_fdt.h: s/of_setup/setup_of
  - unflatten_device_tree(): validate size in header field dtb_empty_root
    that will be used to copy dtb_empty_root
  - add Kconfig option to manually select CONFIG_OF_EARLY_FLATTREE

Changes since version 1: (patch 2/2)
  - refresh for 6.2-rc1
  - update Signed-off-by
  - fix formatting error (leading space) in patch comment

Frank Rowand (2):
  of: create of_root if no dtb provided
  of: unittest: treat missing of_root as error instead of fixing up

 drivers/of/Kconfig        |  7 ++++++-
 drivers/of/Makefile       |  2 +-
 drivers/of/empty_root.dts |  6 ++++++
 drivers/of/fdt.c          | 27 ++++++++++++++++++++++++++-
 drivers/of/unittest.c     | 16 ++++++----------
 include/linux/of_fdt.h    |  2 ++
 init/main.c               |  2 ++
 7 files changed, 49 insertions(+), 13 deletions(-)
 create mode 100644 drivers/of/empty_root.dts

-- 
Frank Rowand <frowand.list@gmail.com>

[PATCH 1/2] of: create of_root if no dtb provided

[Frank Rowand]

When enabling CONFIG_OF on a platform where of_root is not populated by
firmware, we end up without a root node. In order to apply overlays and
create subnodes of the root node, we need one. Create this root node
by unflattening an empty builtin dtb.

If firmware provides a flattened device tree (FDT) then the FDT is
unflattened via setup_arch().  Otherwise, setup_of() which is called
immediately after setup_arch(), and will create the default root node
if it does not exist.

Signed-off-by: Frank Rowand <frowand.list@gmail.com>
---

There are checkpatch warnings.  I have reviewed them and feel
they can be ignored.

Changes since version 1:
  - refresh for 6.2-rc1
  - update Signed-off-by
  - fix typo in of_fdt.h: s/of_setup/setup_of
  - unflatten_device_tree(): validate size in header field dtb_empty_root
    that will be used to copy dtb_empty_root
  - add Kconfig option to manually select CONFIG_OF_EARLY_FLATTREE

 drivers/of/Kconfig        |  7 ++++++-
 drivers/of/Makefile       |  2 +-
 drivers/of/empty_root.dts |  6 ++++++
 drivers/of/fdt.c          | 27 ++++++++++++++++++++++++++-
 include/linux/of_fdt.h    |  2 ++
 init/main.c               |  2 ++
 6 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 drivers/of/empty_root.dts

diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index 80b5fd44ab1c..591cfe386727 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -42,9 +42,14 @@ config OF_FLATTREE
 	select CRC32
 
 config OF_EARLY_FLATTREE
-	bool
+	bool "Functions for accessing Flat Devicetree (FDT) early in boot"
 	select DMA_DECLARE_COHERENT if HAS_DMA
 	select OF_FLATTREE
+	help
+	  Normally selected by platforms that process an FDT that has been
+	  passed to the kernel by the bootloader.  If the bootloader does not
+	  pass an FDT to the kernel and you need an empty devicetree that
+	  contains only a root node to exist, then say Y here.
 
 config OF_PROMTREE
 	bool
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index e0360a44306e..cbae92c5ed02 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -2,7 +2,7 @@
 obj-y = base.o device.o platform.o property.o
 obj-$(CONFIG_OF_KOBJ) += kobj.o
 obj-$(CONFIG_OF_DYNAMIC) += dynamic.o
-obj-$(CONFIG_OF_FLATTREE) += fdt.o
+obj-$(CONFIG_OF_FLATTREE) += fdt.o empty_root.dtb.o
 obj-$(CONFIG_OF_EARLY_FLATTREE) += fdt_address.o
 obj-$(CONFIG_OF_PROMTREE) += pdt.o
 obj-$(CONFIG_OF_ADDRESS)  += address.o
diff --git a/drivers/of/empty_root.dts b/drivers/of/empty_root.dts
new file mode 100644
index 000000000000..cf9e97a60f48
--- /dev/null
+++ b/drivers/of/empty_root.dts
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/dts-v1/;
+
+/ {
+
+};
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index b2272bccf85c..0d2f6d016b7e 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -33,6 +33,13 @@
 
 #include "of_private.h"
 
+/*
+ * __dtb_empty_root_begin[] and __dtb_empty_root_end[] magically created by
+ * cmd_dt_S_dtb in scripts/Makefile.lib
+ */
+extern void *__dtb_empty_root_begin;
+extern void *__dtb_empty_root_end;
+
 /*
  * of_fdt_limit_memory - limit the number of regions in the /memory node
  * @limit: maximum entries
@@ -1326,8 +1333,19 @@ bool __init early_init_dt_scan(void *params)
  */
 void __init unflatten_device_tree(void)
 {
-	__unflatten_device_tree(initial_boot_params, NULL, &of_root,
+	if (!initial_boot_params) {
+		initial_boot_params = (void *) __dtb_empty_root_begin;
+		/* fdt_totalsize() will be used for copy size */
+		if (fdt_totalsize(initial_boot_params) >
+		    __dtb_empty_root_end - __dtb_empty_root_begin) {
+			pr_err("invalid size in dtb_empty_root\n");
+			return;
+		}
+		unflatten_and_copy_device_tree();
+	} else {
+		__unflatten_device_tree(initial_boot_params, NULL, &of_root,
 				early_init_dt_alloc_memory_arch, false);
+	}
 
 	/* Get pointer to "/chosen" and "/aliases" nodes for use everywhere */
 	of_alias_scan(early_init_dt_alloc_memory_arch);
@@ -1367,6 +1385,13 @@ void __init unflatten_and_copy_device_tree(void)
 	unflatten_device_tree();
 }
 
+void __init setup_of(void)
+{
+	/* if architecture did not unflatten devicetree, do it now */
+	if (!of_root)
+		unflatten_device_tree();
+}
+
 #ifdef CONFIG_SYSFS
 static ssize_t of_fdt_raw_read(struct file *filp, struct kobject *kobj,
 			       struct bin_attribute *bin_attr,
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index d69ad5bb1eb1..f0dc46d576da 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -81,6 +81,7 @@ extern const void *of_flat_dt_match_machine(const void *default_match,
 /* Other Prototypes */
 extern void unflatten_device_tree(void);
 extern void unflatten_and_copy_device_tree(void);
+extern void setup_of(void);
 extern void early_init_devtree(void *);
 extern void early_get_first_memblock_info(void *, phys_addr_t *);
 #else /* CONFIG_OF_EARLY_FLATTREE */
@@ -91,6 +92,7 @@ static inline void early_init_fdt_reserve_self(void) {}
 static inline const char *of_flat_dt_get_machine_name(void) { return NULL; }
 static inline void unflatten_device_tree(void) {}
 static inline void unflatten_and_copy_device_tree(void) {}
+static inline void setup_of(void) {}
 #endif /* CONFIG_OF_EARLY_FLATTREE */
 
 #endif /* __ASSEMBLY__ */
diff --git a/init/main.c b/init/main.c
index e1c3911d7c70..31e0931b5134 100644
--- a/init/main.c
+++ b/init/main.c
@@ -101,6 +101,7 @@
 #include <linux/init_syscalls.h>
 #include <linux/stackdepot.h>
 #include <linux/randomize_kstack.h>
+#include <linux/of_fdt.h>
 #include <net/net_namespace.h>
 
 #include <asm/io.h>
@@ -961,6 +962,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	pr_notice("%s", linux_banner);
 	early_security_init();
 	setup_arch(&command_line);
+	setup_of();
 	setup_boot_config();
 	setup_command_line(command_line);
 	setup_nr_cpu_ids();
-- 
Frank Rowand <frowand.list@gmail.com>

[PATCH 2/2] of: unittest: treat missing of_root as error instead of fixing up

[Frank Rowand]

setup_of() now ensures that of_root node is populated with the
root of a default devicetree. Remove the unittest code that
created of_root if it was missing.  Verify that of_root is
valid before attempting to attach the testcase-data subtree.

Signed-off-by: Frank Rowand <frowand.list@gmail.com>
---
Changes since version 1:
  - refresh for 6.2-rc1
  - update Signed-off-by
  - fix formatting error (leading space) in patch comment

 drivers/of/unittest.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index bc0f1e50a4be..006713511c53 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -1469,20 +1469,16 @@ static int __init unittest_data_add(void)
 		return -EINVAL;
 	}
 
-	if (!of_root) {
-		of_root = unittest_data_node;
-		for_each_of_allnodes(np)
-			__of_attach_node_sysfs(np);
-		of_aliases = of_find_node_by_path("/aliases");
-		of_chosen = of_find_node_by_path("/chosen");
-		of_overlay_mutex_unlock();
-		return 0;
-	}
-
 	EXPECT_BEGIN(KERN_INFO,
 		     "Duplicate name in testcase-data, renamed to \"duplicate-name#1\"");
 
 	/* attach the sub-tree to live tree */
+	if (!of_root) {
+		pr_warn("%s: no live tree to attach sub-tree\n", __func__);
+		kfree(unittest_data);
+		return -ENODEV;
+	}
+
 	np = unittest_data_node->child;
 	while (np) {
 		struct device_node *next = np->sibling;
-- 
Frank Rowand <frowand.list@gmail.com>

Re: [PATCH 0/2] of: populate of_root_node if not set (alternate)

[Frank Rowand]

On 2/21/23 21:54, Frank Rowand wrote:
> This series is a different implementation to achieve the goals of
> https://lore.kernel.org/r/20220623105044.152832-1-clement.leger@bootlin.com
> 
> In order to apply overlays or create new nodes under the root node, the
> kernel expects of_root to be set. On some system where a device-tree was
> not provided by firmware (x86 for instance) if CONFIG_OF is enabled,
> then we will end up with a null of_root. This series adds support to
> create this root node using a builtin dtb and removes the manual
> creation of the root node done in unittests.c.
> 
> Changes since version 1: (patch 1/2)

Email subject lines should have said "v2".  I resent the series with the "v2".

-Frank

>   - refresh for 6.2-rc1
>   - update Signed-off-by
>   - fix typo in of_fdt.h: s/of_setup/setup_of
>   - unflatten_device_tree(): validate size in header field dtb_empty_root
>     that will be used to copy dtb_empty_root
>   - add Kconfig option to manually select CONFIG_OF_EARLY_FLATTREE
> 
> Changes since version 1: (patch 2/2)
>   - refresh for 6.2-rc1
>   - update Signed-off-by
>   - fix formatting error (leading space) in patch comment
> 
> Frank Rowand (2):
>   of: create of_root if no dtb provided
>   of: unittest: treat missing of_root as error instead of fixing up
> 
>  drivers/of/Kconfig        |  7 ++++++-
>  drivers/of/Makefile       |  2 +-
>  drivers/of/empty_root.dts |  6 ++++++
>  drivers/of/fdt.c          | 27 ++++++++++++++++++++++++++-
>  drivers/of/unittest.c     | 16 ++++++----------
>  include/linux/of_fdt.h    |  2 ++
>  init/main.c               |  2 ++
>  7 files changed, 49 insertions(+), 13 deletions(-)
>  create mode 100644 drivers/of/empty_root.dts
>