1 files changed, 69 insertions, 0 deletions
diff --git a/payloads/libpayload/drivers/nvram.c b/payloads/libpayload/drivers/nvram.c
new file mode 100644
index 0000000000..3789c09b3c
--- /dev/null
+++ b/payloads/libpayload/drivers/nvram.c
@@ -0,0 +1,69 @@
+/*
+ * This file is part of the libpayload project.
+ *
+ * Copyright (C) 2008 Uwe Hermann <uwe@hermann-uwe.de>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Datasheet:
+ *  - Name: MC146818: Real-time Clock Plus RAM (RTC)
+ *  - PDF: http://www.freescale.com/files/microcontrollers/doc/data_sheet/MC146818.pdf
+ *  - Order number: MC146818/D
+ */
+
+/*
+ * See also:
+ * http://bochs.sourceforge.net/techspec/CMOS-reference.txt
+ * http://www.bioscentral.com/misc/cmosmap.htm
+ */
+
+#include <libpayload.h>
+
+#define RTC_PORT 0x70
+
+/**
+ * Read a byte from the specified NVRAM address.
+ * 
+ * @param addr The NVRAM address to read a byte from.
+ * @return The byte at the given NVRAM address.
+ */
+u8 nvram_read(u8 addr)
+{
+	outb(addr, RTC_PORT);
+	return inb(RTC_PORT + 1);
+}
+
+/**
+ * Write a byte to the specified NVRAM address.
+ * 
+ * @param val The byte to write to NVRAM.
+ * @param addr The NVRAM address to write to.
+ */
+void nvram_write(u8 val, u8 addr)
+{
+	outb(addr, RTC_PORT);
+	outb(val, RTC_PORT + 1);
+}