Revert "Staging: olpc_dcon: Remove obsolete driver"

This reverts commit 82ef33a.  It turns
out these machines are still out there, and the original patch broke
them.  So revert it, adding back the driver, so people's machines still
work properly.

Reported-by: James Cameron <quozl@laptop.org>
Cc: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -10583,6 +10583,14 @@ L:	linux-tegra@vger.kernel.org
 S:	Maintained
 F:	drivers/staging/nvec/
 
+STAGING - OLPC SECONDARY DISPLAY CONTROLLER (DCON)
+M:	Jens Frederich <jfrederich@gmail.com>
+M:	Daniel Drake <dsd@laptop.org>
+M:	Jon Nettleton <jon.nettleton@gmail.com>
+W:	http://wiki.laptop.org/go/DCON
+S:	Maintained
+F:	drivers/staging/olpc_dcon/
+
 STAGING - REALTEK RTL8712U DRIVERS
 M:	Larry Finger <Larry.Finger@lwfinger.net>
 M:	Florian Schilhabel <florian.c.schilhabel@googlemail.com>.

drivers/staging/Kconfig

@@ -30,6 +30,8 @@ source "drivers/staging/wlan-ng/Kconfig"
 
 source "drivers/staging/comedi/Kconfig"
 
+source "drivers/staging/olpc_dcon/Kconfig"
+
 source "drivers/staging/rtl8192u/Kconfig"
 
 source "drivers/staging/rtl8192e/Kconfig"

drivers/staging/Makefile

@@ -4,6 +4,7 @@ obj-y				+= media/
 obj-$(CONFIG_SLICOSS)		+= slicoss/
 obj-$(CONFIG_PRISM2_USB)	+= wlan-ng/
 obj-$(CONFIG_COMEDI)		+= comedi/
+obj-$(CONFIG_FB_OLPC_DCON)	+= olpc_dcon/
 obj-$(CONFIG_RTL8192U)		+= rtl8192u/
 obj-$(CONFIG_RTL8192E)		+= rtl8192e/
 obj-$(CONFIG_R8712U)		+= rtl8712/

drivers/staging/olpc_dcon/Kconfig

@@ -0,0 +1,35 @@
+config FB_OLPC_DCON
+	tristate "One Laptop Per Child Display CONtroller support"
+	depends on OLPC && FB
+	depends on I2C
+	depends on (GPIO_CS5535 || GPIO_CS5535=n)
+	select BACKLIGHT_CLASS_DEVICE
+	---help---
+	  In order to support very low power operation, the XO laptop uses a
+	  secondary Display CONtroller, or DCON.  This secondary controller
+	  is present in the video pipeline between the primary display
+	  controller (integrate into the processor or chipset) and the LCD
+	  panel.  It allows the main processor/display controller to be
+	  completely powered off while still retaining an image on the display.
+	  This controller is only available on OLPC platforms.  Unless you have
+	  one of these platforms, you will want to say 'N'.
+
+config FB_OLPC_DCON_1
+	bool "OLPC XO-1 DCON support"
+	depends on FB_OLPC_DCON && GPIO_CS5535
+	default y
+	---help---
+	  Enable support for the DCON in XO-1 model laptops.  The kernel
+	  communicates with the DCON using model-specific code.  If you
+	  have an XO-1 (or if you're unsure what model you have), you should
+	  say 'Y'.
+
+config FB_OLPC_DCON_1_5
+	bool "OLPC XO-1.5 DCON support"
+	depends on FB_OLPC_DCON && ACPI
+	default y
+	---help---
+	  Enable support for the DCON in XO-1.5 model laptops.  The kernel
+	  communicates with the DCON using model-specific code.  If you
+	  have an XO-1.5 (or if you're unsure what model you have), you
+	  should say 'Y'.

drivers/staging/olpc_dcon/Makefile

@@ -0,0 +1,6 @@
+olpc-dcon-objs += olpc_dcon.o
+olpc-dcon-$(CONFIG_FB_OLPC_DCON_1)	+= olpc_dcon_xo_1.o
+olpc-dcon-$(CONFIG_FB_OLPC_DCON_1_5)	+= olpc_dcon_xo_1_5.o
+obj-$(CONFIG_FB_OLPC_DCON)	+= olpc-dcon.o
+
+

drivers/staging/olpc_dcon/TODO

@@ -0,0 +1,9 @@
+TODO:
+	- see if vx855 gpio API can be made similar enough to cs5535 so we can
+	  share more code
+	- allow simultaneous XO-1 and XO-1.5 support
+
+Please send patches to Greg Kroah-Hartman <greg@kroah.com> and
+copy:
+	Daniel Drake <dsd@laptop.org>
+	Jens Frederich <jfrederich@gmail.com>