mfd / platform: cros_ec: Move vbc attributes to its own driver

The entire way how cros sysfs attibutes are created is broken.
cros_ec_vbc should be its own driver and its attributes should be
associated with a vbc driver not the mfd driver. In order to retain
the path, the vbc attributes are attached to the cros_class.

The patch also adds the sysfs documentation.

Signed-off-by: Enric Balletbo i Serra <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

Documentation/ABI/testing/sysfs-class-chromeos-driver-cros-ec-vbc

···
+What:		/sys/class/chromeos/<ec-device-name>/vbc/vboot_context
+Date:		October 2015
+KernelVersion:	4.4
+Description:
+		Read/write the verified boot context data included on a
+		small nvram space on some EC implementations.

drivers/mfd/cros_ec_dev.c

···
 
 static const struct attribute_group *cros_ec_groups[] = {
 	&cros_ec_attr_group,
-	&cros_ec_vbc_attr_group,
 	NULL,
 };
 
···
 
 static const struct mfd_cell cros_ec_platform_cells[] = {
 	{ .name = "cros-ec-lightbar" },
+	{ .name = "cros-ec-vbc" },
 };
 
 static int ec_device_probe(struct platform_device *pdev)

drivers/platform/chrome/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called cros_ec_lightbar.
 
+config CROS_EC_VBC
+	tristate "ChromeOS EC vboot context support"
+	depends on MFD_CROS_EC_CHARDEV && OF
+	default MFD_CROS_EC_CHARDEV
+	help
+	  This option exposes the ChromeOS EC vboot context nvram to
+	  userspace.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called cros_ec_vbc.
+
 endif # CHROMEOS_PLATFORMS

drivers/platform/chrome/Makefile

···
 obj-$(CONFIG_CHROMEOS_PSTORE)		+= chromeos_pstore.o
 obj-$(CONFIG_CHROMEOS_TBMC)		+= chromeos_tbmc.o
 cros_ec_ctl-objs			:= cros_ec_sysfs.o \
-					   cros_ec_vbc.o cros_ec_debugfs.o
+					   cros_ec_debugfs.o
 obj-$(CONFIG_CROS_EC_CTL)		+= cros_ec_ctl.o
 obj-$(CONFIG_CROS_EC_I2C)		+= cros_ec_i2c.o
 obj-$(CONFIG_CROS_EC_SPI)		+= cros_ec_spi.o
···
 obj-$(CONFIG_CROS_EC_PROTO)		+= cros_ec_proto.o
 obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)	+= cros_kbd_led_backlight.o
 obj-$(CONFIG_CROS_EC_LIGHTBAR)		+= cros_ec_lightbar.o
+obj-$(CONFIG_CROS_EC_VBC)		+= cros_ec_vbc.o

drivers/platform/chrome/cros_ec_vbc.c

···
 #include <linux/platform_device.h>
 #include <linux/mfd/cros_ec.h>
 #include <linux/mfd/cros_ec_commands.h>
+#include <linux/module.h>
 #include <linux/slab.h>
+
+#define DRV_NAME "cros-ec-vbc"
 
 static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
 				  struct bin_attribute *att, char *buf,
···
 	.bin_attrs = cros_ec_vbc_bin_attrs,
 	.is_bin_visible = cros_ec_vbc_is_visible,
 };
-EXPORT_SYMBOL(cros_ec_vbc_attr_group);
+
+static int cros_ec_vbc_probe(struct platform_device *pd)
+{
+	struct cros_ec_dev *ec_dev = dev_get_drvdata(pd->dev.parent);
+	struct device *dev = &pd->dev;
+	int ret;
+
+	ret = sysfs_create_group(&ec_dev->class_dev.kobj,
+				 &cros_ec_vbc_attr_group);
+	if (ret < 0)
+		dev_err(dev, "failed to create %s attributes. err=%d\n",
+			cros_ec_vbc_attr_group.name, ret);
+
+	return ret;
+}
+
+static int cros_ec_vbc_remove(struct platform_device *pd)
+{
+	struct cros_ec_dev *ec_dev = dev_get_drvdata(pd->dev.parent);
+
+	sysfs_remove_group(&ec_dev->class_dev.kobj,
+			   &cros_ec_vbc_attr_group);
+
+	return 0;
+}
+
+static struct platform_driver cros_ec_vbc_driver = {
+	.driver = {
+		.name = DRV_NAME,
+	},
+	.probe = cros_ec_vbc_probe,
+	.remove = cros_ec_vbc_remove,
+};
+
+module_platform_driver(cros_ec_vbc_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Expose the vboot context nvram to userspace");
+MODULE_ALIAS("platform:" DRV_NAME);

include/linux/mfd/cros_ec.h

···
 
 /* sysfs stuff */
 extern struct attribute_group cros_ec_attr_group;
-extern struct attribute_group cros_ec_vbc_attr_group;
 
 /* debugfs stuff */
 int cros_ec_debugfs_init(struct cros_ec_dev *ec);