mfd / platform: cros_ec: Handle chained ECs as platform devices

An MFD is a device that contains several sub-devices (cells). For instance,
the ChromeOS EC fits in this description as usually contains a charger and
can have other devices with different functions like a Real-Time Clock,
an Audio codec, a Real-Time Clock, ...

If you look at the driver, though, we're doing something odd. We have
two MFD cros-ec drivers where one of them (cros-ec-core) instantiates
another MFD driver as sub-driver (cros-ec-dev), and the latest
instantiates the different sub-devices (Real-Time Clock, Audio codec,
etc).

                  MFD
------------------------------------------
   cros-ec-core
       |___ mfd-cellA (cros-ec-dev)
       |       |__ mfd-cell0
       |       |__ mfd-cell1
       |       |__ ...
       |
       |___ mfd-cellB (cros-ec-dev)
               |__ mfd-cell0
               |__ mfd-cell1
               |__ ...

The problem that was trying to solve is to describe some kind of topology for
the case where we have an EC (cros-ec) chained with another EC
(cros-pd). Apart from that this extends the bounds of what MFD was
designed to do we might be interested on have other kinds of topology that
can't be implemented in that way.

Let's prepare the code to move the cros-ec-core part from MFD to
platform/chrome as this is clearly a platform specific thing non-related
to a MFD device.

  platform/chrome  |         MFD
------------------------------------------
                   |
   cros-ec ________|___ cros-ec-dev
                   |       |__ mfd-cell0
                   |       |__ mfd-cell1
                   |       |__ ...
                   |
   cros-pd ________|___ cros-ec-dev
                   |        |__ mfd-cell0
                   |        |__ mfd-cell1
                   |        |__ ...

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index 77805c3f2de7..bcccda0257ff 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -121,6 +121,10 @@ struct cros_ec_command {
  * @event_data: Raw payload transferred with the MKBP event.
  * @event_size: Size in bytes of the event data.
  * @host_event_wake_mask: Mask of host events that cause wake from suspend.
+ * @ec: The platform_device used by the mfd driver to interface with the
+ *      main EC.
+ * @pd: The platform_device used by the mfd driver to interface with the
+ *      PD behind an EC.
  */
 struct cros_ec_device {
 	/* These are used by other drivers that want to talk to the EC */
@@ -157,6 +161,10 @@ struct cros_ec_device {
 	int event_size;
 	u32 host_event_wake_mask;
 	u32 last_resume_result;
+
+	/* The platform devices used by the mfd driver */
+	struct platform_device *ec;
+	struct platform_device *pd;
 };
 
 /**
@@ -292,6 +300,16 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
 int cros_ec_register(struct cros_ec_device *ec_dev);
 
 /**
+ * cros_ec_unregister() - Remove a ChromeOS EC.
+ * @ec_dev: Device to unregister.
+ *
+ * Call this to deregister a ChromeOS EC, then clean up any private data.
+ *
+ * Return: 0 on success or negative error code.
+ */
+int cros_ec_unregister(struct cros_ec_device *ec_dev);
+
+/**
  * cros_ec_query_all() -  Query the protocol version supported by the
  *         ChromeOS EC.
  * @ec_dev: Device to register.