efi: Update some comments related to smbios tables

Clarify the operation of this code with some additional comments.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

include/efi_loader.h

@@ -214,6 +214,13 @@ efi_status_t efi_net_register(void);
 /* Called by bootefi to make the watchdog available */
 efi_status_t efi_watchdog_register(void);
 /* Called by bootefi to make SMBIOS tables available */
+/**
+ * efi_smbios_register() - write out SMBIOS tables
+ *
+ * Called by bootefi to make SMBIOS tables available
+ *
+ * @return 0 if OK, -ENOMEM if no memory is available for the tables
+ */
 efi_status_t efi_smbios_register(void);
 
 struct efi_simple_file_system_protocol *

include/smbios.h

@@ -231,8 +231,9 @@ typedef int (*smbios_write_type)(ulong *addr, int handle);
  *
  * This writes SMBIOS table at a given address.
  *
- * @addr:	start address to write SMBIOS table
- * @return:	end address of SMBIOS table
+ * @addr:	start address to write SMBIOS table. If this is not
+ *	16-byte-aligned then it will be aligned before the table is written
+ * @return:	end address of SMBIOS table (and start address for next entry)
  */
 ulong write_smbios_table(ulong addr);
 

lib/efi_loader/efi_smbios.c

@@ -29,7 +29,12 @@ efi_status_t efi_smbios_register(void)
 	if (ret != EFI_SUCCESS)
 		return ret;
 
-	/* Generate SMBIOS tables */
+	/*
+	 * Generate SMBIOS tables - we know that efi_allocate_pages() returns
+	 * a 4k-aligned address, so it is safe to assume that
+	 * write_smbios_table() will write the table at that address.
+	 */
+	assert(!(dmi & 0xf));
 	write_smbios_table(dmi);
 
 	/* And expose them to our EFI payload */