From: Dirk Brandewie <dirk.brande...@gmail.com>
Adds a kernel command line option "dtb_compat=<string>" and functions
for architecture/platform specific code to retrieve the command line
string and locate the compatible DTB linked into the kernel
of_flat_dt_get_dtb_compatible_string() returns a pointer string passed
from the command line or a pointer to an empty string.
of_flat_dt_find_compatible_dtb() returns a pointer to a DTB that is
compatible with the "compatible" string or a NULL pointer if no
matching DTB is present.
Signed-off-by: Dirk Brandewie <dirk.brande...@gmail.com>
---
Documentation/kernel-parameters.txt | 7 +++++
drivers/of/fdt.c | 52 +++++++++++++++++++++++++++++++++++
include/linux/of_fdt.h | 4 +++
3 files changed, 63 insertions(+), 0 deletions(-)
diff --git a/Documentation/kernel-parameters.txt
b/Documentation/kernel-parameters.txt
index ed45e98..f9b77fa 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -655,6 +655,13 @@ and is between 256 and 4096 characters. It is defined in
the file
dscc4.setup= [NET]
+ dtb_compat= [KNL]
+ Specify the "compatible" string for the device
+ tree blob present in the kernel image. This
+ string will be used to select the first device
+ tree blob whose compatible property matches
+ the string passed on the kernel commandline.
+
dynamic_printk Enables pr_debug()/dev_dbg() calls if
CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
These can also be switched on/off via
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index c1360e0..c0858ce 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -15,6 +15,8 @@
#include <linux/of_fdt.h>
#include <linux/string.h>
#include <linux/errno.h>
+#include <asm-generic/vmlinux.lds.h>
+
#ifdef CONFIG_PPC
#include <asm/machdep.h>
@@ -604,3 +606,53 @@ void __init unflatten_device_tree(void)
pr_debug(" <- unflatten_device_tree()\n");
}
+
+#define MAX_DTB_COMPAT_STR 64
+char dtb_compat_name[MAX_DTB_COMPAT_STR] = "";
+
+char __init *of_flat_dt_get_dtb_compatible_string(void)
+{
+ return dtb_compat_name;
+}
+
+
+extern uint8_t __dtb_start[];
+extern uint8_t __dtb_end[];
+void __init *of_flat_dt_find_compatible_dtb(char *name)
+{
+ void *rc = NULL;
+ unsigned long root, size;
+ struct boot_param_header *orig_initial_boot_params;
+ uint8_t *blob;
+
+ orig_initial_boot_params = initial_boot_params;
+ blob = __dtb_start;
+ initial_boot_params = (struct boot_param_header *)blob;
+
+ while (blob < __dtb_end &&
+ (be32_to_cpu(initial_boot_params->magic) == OF_DT_HEADER)) {
+ root = of_get_flat_dt_root();
+ if (of_flat_dt_is_compatible(root, name) > 0) {
+ rc = blob;
+ break;
+ }
+
+ size = be32_to_cpu(initial_boot_params->totalsize);
+ blob = PTR_ALIGN(blob + size, DTB_ALIGNMENT);
+ initial_boot_params = (struct boot_param_header *)blob;
+ }
+
+ if (rc == NULL)
+ initial_boot_params = orig_initial_boot_params;
+ return rc;
+}
+
+
+static int __init of_flat_dtb_compat_setup(char *line)
+{
+ strncpy(dtb_compat_name, line, MAX_DTB_COMPAT_STR);
+ return 1;
+}
+
+early_param("dtb_compat", of_flat_dtb_compat_setup);
+
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index 7bbf5b3..29561f4 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -58,6 +58,7 @@ struct boot_param_header {
};
#if defined(CONFIG_OF_FLATTREE)
+
/* TBD: Temporary export of fdt globals - remove when code fully merged */
extern int __initdata dt_root_addr_cells;
extern int __initdata dt_root_size_cells;
@@ -82,6 +83,9 @@ extern void early_init_dt_add_memory_arch(u64 base, u64 size);
extern u64 early_init_dt_alloc_memory_arch(u64 size, u64 align);
extern u64 dt_mem_next_cell(int s, __be32 **cellp);
+extern char *of_flat_dt_get_dtb_compatible_string(void);
+extern void *of_flat_dt_find_compatible_dtb(char *name);
+
/*
* If BLK_DEV_INITRD, the fdt early init code will call this function,
* to be provided by the arch code. start and end are specified as
--
1.7.2.3
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