Subject: [PATCH v16 09/12] of: Define functions to allocate and free FDT

From: Lakshmi Ramasubramanian <[email-masked]>
Date: Thu, 4 Feb 2021 08:41:32 -0800

Kernel components that use Flattened Device Tree (FDT) allocate kernel
memory and call fdt_open_into() to reorganize the tree into a form
suitable for the read-write operations.  These operations can be
combined into a single function to allocate and initialize the FDT
so the different architecures do not have to duplicate the code.

Define of_alloc_and_init_fdt() and of_free_fdt() in drivers/of/kexec.c
to allocate and initialize FDT, and to free the FDT buffer respectively.

Signed-off-by: Lakshmi Ramasubramanian <[email-masked]>
Suggested-by: Rob Herring <[email-masked]>
Suggested-by: Joe Perches <[email-masked]>
---
 drivers/of/kexec.c | 37 +++++++++++++++++++++++++++++++++++++
 include/linux/of.h |  2 ++
 2 files changed, 39 insertions(+)

diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index 5ae0e5d90f55..197e71104f47 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -11,6 +11,7 @@
 
 #include <linux/kernel.h>
 #include <linux/kexec.h>
+#include <linux/mm.h>
 #include <linux/memblock.h>
 #include <linux/libfdt.h>
 #include <linux/of.h>
@@ -28,6 +29,42 @@
 #define FDT_PROP_RNG_SEED	"rng-seed"
 #define RNG_SEED_SIZE		128
 
+/**
+ * of_alloc_and_init_fdt - Allocate and initialize a Flattened device tree
+ *
+ * @fdt_size:	Flattened device tree size
+ *
+ * Return the allocated FDT buffer on success, or NULL on error.
+ */
+void *of_alloc_and_init_fdt(unsigned int fdt_size)
+{
+	void *fdt;
+	int ret;
+
+	fdt = kvmalloc(fdt_size, GFP_KERNEL);
+	if (!fdt)
+		return NULL;
+
+	ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
+	if (ret < 0) {
+		pr_err("Error setting up the new device tree.\n");
+		kvfree(fdt);
+		fdt = NULL;
+	}
+
+	return fdt;
+}
+
+/**
+ * of_free_fdt - Free the buffer for Flattened device tree
+ *
+ * @fdt:	Flattened device tree buffer to free
+ */
+void of_free_fdt(void *fdt)
+{
+	kvfree(fdt);
+}
+
 /**
  * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
  *
diff --git a/include/linux/of.h b/include/linux/of.h
index 19f77dd12507..9f0261761e28 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -563,6 +563,8 @@ struct kimage;
 int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
 			   unsigned long initrd_load_addr, unsigned long initrd_len,
 			   const char *cmdline);
+void *of_alloc_and_init_fdt(unsigned int fdt_size);
+void of_free_fdt(void *fdt);
 
 #ifdef CONFIG_IMA_KEXEC
 int of_ima_add_kexec_buffer(struct kimage *image,
-- 
2.30.0