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, 5 insertions, 0 deletions

diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h
index af171f5f0635..9cd0bac9ceb9 100644
--- a/drivers/staging/greybus/connection.h
+++ b/drivers/staging/greybus/connection.h
@@ -58,6 +58,8 @@ struct gb_connection {
 	atomic_t			op_cycle;
 
 	void				*private;
+
+	bool				mode_switch;
 };
 
 struct gb_connection *gb_connection_create_static(struct gb_host_device *hd,
@@ -83,6 +85,9 @@ void gb_connection_disable_rx(struct gb_connection *connection);
 void gb_connection_disable(struct gb_connection *connection);
 void gb_connection_disable_forced(struct gb_connection *connection);
 
+void gb_connection_mode_switch_prepare(struct gb_connection *connection);
+void gb_connection_mode_switch_complete(struct gb_connection *connection);
+
 void greybus_data_rcvd(struct gb_host_device *hd, u16 cport_id,
 			u8 *data, size_t length);