ACPI: Provide /sys/kernel/debug/ec/...

This patch provides the same information through debugfs, which previously was
provided through /proc/acpi/embedded_controller/*/info

This is the gpe the EC is connected to and whether the global lock
gets used.
The io ports used are added to /proc/ioports in another patch.
Beside the fact that /proc/acpi is deprecated for quite some time,
this info is not needed for applications and thus can be moved
to debugfs instead of a public interface like /sys.

Signed-off-by: Thomas Renninger <trenn@suse.de>

CC: Alexey Starikovskiy <astarikovskiy@suse.de>
CC: Len Brown <lenb@kernel.org>
CC: linux-kernel@vger.kernel.org
CC: linux-acpi@vger.kernel.org
CC: Bjorn Helgaas <bjorn.helgaas@hp.com>
CC: platform-driver-x86@vger.kernel.org
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/acpi/Kconfig

@@ -104,6 +104,19 @@ config ACPI_SYSFS_POWER
 	help
 	  Say N to disable power /sys interface
 
+config ACPI_EC_DEBUGFS
+	tristate "EC read/write access through /sys/kernel/debug/ec"
+	default y
+	help
+	  Say N to disable Embedded Controller /sys/kernel/debug interface
+
+	  An Embedded Controller typically is available on laptops and reads
+	  sensor values like battery state and temperature.
+	  The kernel access the EC through ACPI parsed code provided by BIOS
+	  tables.
+	  Thus this option is a debug option that helps to write ACPI drivers
+	  and can be used to identify ACPI code or EC firmware bugs.
+
 config ACPI_PROC_EVENT
 	bool "Deprecated /proc/acpi/event support"
 	depends on PROC_FS