memory_accessor: new interface for reading/writing persistent memory

This patch adds an interface by which other kernel code can read/write
persistent memory such as I2C or SPI EEPROMs, or devices which provide
NVRAM.  Use cases include storage of board-specific configuration data
like Ethernet addresses and sensor calibrations.

Original idea, review and improvement suggestions by David Brownell.
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

include/linux/memory.h

@@ -99,4 +99,15 @@ enum mem_add_context { BOOT, HOTPLUG };
 #define hotplug_memory_notifier(fn, pri) do { } while (0)
 #endif
 
+/*
+ * 'struct memory_accessor' is a generic interface to provide
+ * in-kernel access to persistent memory such as i2c or SPI EEPROMs
+ */
+struct memory_accessor {
+	ssize_t (*read)(struct memory_accessor *, char *buf, off_t offset,
+			size_t count);
+	ssize_t (*write)(struct memory_accessor *, const char *buf,
+			 off_t offset, size_t count);
+};
+
 #endif /* _LINUX_MEMORY_H_ */