usb: typec: Implement mode selection

The mode selection process is controlled by the following API functions,
which allow to initiate and complete mode entry based on the priority of
each mode:

`typec_mode_selection_start` function compiles a priority list of supported
Alternate Modes.
`typec_altmode_state_update` function is invoked by the port driver to
communicate the current mode of the Type-C connector.
`typec_mode_selection_delete` function stops the currently running mode
selection process and releases all associated system resources.

`mode_selection_work_fn` task attempts to activate modes. The process stops
on success; otherwise, it proceeds to the next mode after a timeout or
error.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260119131824.2529334-5-akuchynski@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
index 7e6c02d74b54..70026f5f8f99 100644
--- a/include/linux/usb/typec_altmode.h
+++ b/include/linux/usb/typec_altmode.h
@@ -240,4 +240,44 @@ void typec_altmode_unregister_driver(struct typec_altmode_driver *drv);
 	module_driver(__typec_altmode_driver, typec_altmode_register_driver, \
 		      typec_altmode_unregister_driver)
 
+/**
+ * typec_mode_selection_start - Start an alternate mode selection process
+ * @partner: Handle to the Type-C partner device
+ * @delay: Delay between mode entry/exit attempts, ms
+ * @timeout: Timeout for a mode entry attempt, ms
+ *
+ * This function initiates the process of attempting to enter an Alternate Mode
+ * supported by the connected Type-C partner.
+ * Returns 0 on success, or a negative error code on failure.
+ */
+int typec_mode_selection_start(struct typec_partner *partner,
+			       const unsigned int delay, const unsigned int timeout);
+
+/**
+ * typec_altmode_state_update - Report the current status of an Alternate Mode
+ * negotiation
+ * @partner: Handle to the Type-C partner device
+ * @svid: Standard or Vendor ID of the Alternate Mode. A value of 0 should be
+ * passed if no mode is currently active
+ * @result: Result of the entry operation. This should be 0 on success, or a
+ * negative error code if the negotiation failed
+ *
+ * This function should be called by an Alternate Mode driver to report the
+ * result of an asynchronous alternate mode entry request. It signals what the
+ * current active SVID is (or 0 if none) and the success or failure status of
+ * the last attempt.
+ */
+void typec_altmode_state_update(struct typec_partner *partner, const u16 svid,
+				const int result);
+
+/**
+ * typec_mode_selection_delete - Delete an alternate mode selection instance
+ * @partner: Handle to the Type-C partner device.
+ *
+ * This function cancels a pending alternate mode selection request that was
+ * previously started with typec_mode_selection_start().
+ * This is typically called when the partner disconnects.
+ */
+void typec_mode_selection_delete(struct typec_partner *partner);
+
 #endif /* __USB_TYPEC_ALTMODE_H */