greybus: interface: implement generic mode-switch functionality

Add a generic interface for bundle drivers to use to request that a
mode switch is carried out on its behalf.

Mode switching involves tearing down all connections to an interface,
sending a unidirectional mode-switch request, and waiting for a mailbox
event that triggers deferred control connection reset and re-enumeration
of the interface. In case of a timeout waiting for the interface mailbox
event, or on other errors, the interface is powered off.

All of this needs to be done by core from work-queue context in order
not to block incoming SVC requests and bundle-device tear down. Care
must also be taken to serialise against concurrent module removal events
and eject requests.

Special handling of legacy mode-switching is also added in order to
continue to support the ES3 bootrom.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/staging/greybus/control.c b/drivers/staging/greybus/control.c
index 3e02bbb..d772c27 100644
--- a/drivers/staging/greybus/control.c
+++ b/drivers/staging/greybus/control.c
@@ -364,7 +364,24 @@ void gb_control_del(struct gb_control *control)
 		device_del(&control->dev);
 }
 
+struct gb_control *gb_control_get(struct gb_control *control)
+{
+	get_device(&control->dev);
+
+	return control;
+}
+
 void gb_control_put(struct gb_control *control)
 {
 	put_device(&control->dev);
 }
+
+void gb_control_mode_switch_prepare(struct gb_control *control)
+{
+	gb_connection_mode_switch_prepare(control->connection);
+}
+
+void gb_control_mode_switch_complete(struct gb_control *control)
+{
+	gb_connection_mode_switch_complete(control->connection);
+}