efi: add helper function to get UEFI params from FDT

ARM and ARM64 architectures use the device tree to pass UEFI parameters
from stub to kernel. These parameters are things known to the stub but
not discoverable by the kernel after the stub calls ExitBootSerives().
There is a helper function in:

   drivers/firmware/efi/fdt.c

which the stub uses to add the UEFI parameters to the device tree.
This patch adds a complimentary helper function which UEFI runtime
support may use to retrieve the parameters from the device tree.
If an architecture wants to use this helper, it should select
CONFIG_EFI_PARAMS_FROM_FDT.

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 6a4d8e27d1d7..cd0172e796cb 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -664,6 +664,14 @@ struct efi_memory_map {
         unsigned long desc_size;
 };
 
+struct efi_fdt_params {
+        u64 system_table;
+        u64 mmap;
+        u32 mmap_size;
+        u32 desc_size;
+        u32 desc_ver;
+};
+
 typedef struct {
         u32 revision;
         u32 parent_handle;
@@ -861,6 +869,7 @@ extern void efi_initialize_iomem_resources(struct resource *code_resource,
 extern void efi_get_time(struct timespec *now);
 extern int efi_set_rtc_mmss(const struct timespec *now);
 extern void efi_reserve_boot_services(void);
+extern int efi_get_fdt_params(struct efi_fdt_params *params, int verbose);
 extern struct efi_memory_map memmap;
 
 /* Iterate through an efi_memory_map */