Re: [RFC PATCHv2] usb: USB Type-C Connector Class

From: Guenter Roeck
Date: Tue May 24 2016 - 09:42:51 EST


On 05/19/2016 05:44 AM, Heikki Krogerus wrote:
The purpose of this class is to provide unified interface for user
space to get the status and basic information about USB Type-C
Connectors in the system, control data role swapping, and when USB PD
is available, also power role swapping and Alternate Modes.

Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
---
drivers/usb/Kconfig | 2 +
drivers/usb/Makefile | 2 +
drivers/usb/type-c/Kconfig | 7 +
drivers/usb/type-c/Makefile | 1 +
drivers/usb/type-c/typec.c | 957 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/usb/typec.h | 230 +++++++++++
6 files changed, 1199 insertions(+)
create mode 100644 drivers/usb/type-c/Kconfig
create mode 100644 drivers/usb/type-c/Makefile
create mode 100644 drivers/usb/type-c/typec.c
create mode 100644 include/linux/usb/typec.h


Hi,

+/*
+ * struct typec_capability - USB Type-C Port Capabilities
+ * @role: DFP (Host-only), UFP (Device-only) or DRP (Dual Role)
+ * @usb_pd: USB Power Delivery support
+ * @alt_modes: Alternate Modes the connector supports (null terminated)
+ * @audio_accessory: Audio Accessory Adapter Mode support
+ * @debug_accessory: Debug Accessory Mode support
+ * @fix_role: Set a fixed data role for DRP port
+ * @dr_swap: Data Role Swap support
+ * @pr_swap: Power Role Swap support
+ * @vconn_swap: VCONN Swap support
+ * @activate_mode: Enter/exit given Alternate Mode
+ *
+ * Static capabilities of a single USB Type-C port.
+ */
+struct typec_capability {
+ enum typec_data_role role;
+ unsigned int usb_pd:1;
+ struct typec_altmode *alt_modes;
+ unsigned int audio_accessory:1;
+ unsigned int debug_accessory:1;
+
+ int (*fix_role)(struct typec_port *,
+ enum typec_data_role);
+
+ int (*dr_swap)(struct typec_port *);
+ int (*pr_swap)(struct typec_port *);
+ int (*vconn_swap)(struct typec_port *);
+

The function parameter in those calls is all but useless to the caller.
It needs to store the typec_port returned from typec_register(), create a
list of ports, and then search through this list each time one of the
functions is called. This is quite expensive for no good reason.

Previously, with typec_port exported, the called code could use the stored
caps pointer to map to its internal data structures. This is no longer
possible.

I think it would be useful to provide a better means for the called function
to identify its context. Maybe provide a pointer to the private data in
the registration function and use it as parameter in the callback functions ?

Thanks,
Guenter