rtc: add rtc-m41t80 driver

This is a new-style i2c driver for ST M41T80 series RTC chip, derived from
works by Alexander Bigga <ab@mycable.de> who wrote the original
rtc-m41txx.c based on drivers/i2c/chips/m41t00.c driver.

This driver supports M41T8[0-4] and M41ST8[457].  The old m41t00 driver
supports M41T00, M41T81 and M41T85(M41ST85).  While the M41T00 chip is now
supported by rtc-ds1307 driver, this driver does not include support for
the chip.

[akpm@linux-foundation.org: remove bogus `static']
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Alexander Bigga <ab@mycable.de>
Acked-by: Mark A. Greer <mgreer@mvista.com>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -212,6 +212,18 @@ config RTC_DRV_PCF8583
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-pcf8583.
 
+config RTC_DRV_M41T80
+	tristate "ST M41T80 series RTC"
+	depends on RTC_CLASS && I2C
+	help
+	  If you say Y here you will get support for the
+	  ST M41T80 RTC chips series. Currently following chips are
+	  supported: M41T80, M41T81, M41T82, M41T83, M41ST84, M41ST85
+	  and M41ST87.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-m41t80.
+
 comment "SPI RTC drivers"
 	depends on RTC_CLASS && SPI_MASTER
 

drivers/rtc/Makefile

@@ -29,6 +29,7 @@ obj-$(CONFIG_RTC_DRV_PCF8583)	+= rtc-pcf8583.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
 obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
+obj-$(CONFIG_RTC_DRV_M41T80)	+= rtc-m41t80.o
 obj-$(CONFIG_RTC_DRV_M48T86)	+= rtc-m48t86.o
 obj-$(CONFIG_RTC_DRV_DS1553)	+= rtc-ds1553.o
 obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o