On 6/9/2016 10:53 AM, Roger Quadros wrote:

It provides APIs for the following tasks

- Registering an OTG/dual-role capable controller
- Registering Host and Gadget controllers to OTG core
- Providing inputs to and kicking the OTG state machine

Provide a dual-role device (DRD) state machine.
DRD mode is a reduced functionality OTG mode. In this mode
we don't support SRP, HNP and dynamic role-swap.

In DRD operation, the controller mode (Host or Peripheral)
is decided based on the ID pin status. Once a cable plug (Type-A
or Type-B) is attached the controller selects the state
and doesn't change till the cable in unplugged and a different
cable type is inserted.

As we don't need most of the complex OTG states and OTG timers
we implement a lean DRD state machine in usb-otg.c.
The DRD state machine is only interested in 2 hardware inputs
'id' and 'b_sess_vld'.

Signed-off-by: Roger Quadros <redacted>

[...]

[...]

+/**
+ * Change USB protocol when there is a protocol change.
+ * fsm->lock must be held.
+ */

    If you're using the kernel-doc comment, please follow the rules.

+static int drd_set_protocol(struct otg_fsm *fsm, int protocol)

[...]

+/**
+ * Called when entering a DRD state.
+ * fsm->lock must be held.
+ */

    Same here.

+static void drd_set_state(struct otg_fsm *fsm, enum usb_otg_state new_state)

[...]

+/**
+ * DRD state change judgement
+ *
+ * For DRD we're only interested in some of the OTG states
+ * i.e. OTG_STATE_B_IDLE: both peripheral and host are stopped
+ *	OTG_STATE_B_PERIPHERAL: peripheral active
+ *	OTG_STATE_A_HOST: host active
+ * we're only interested in the following inputs
+ *	fsm->id, fsm->b_sess_vld
+ */

    And here.

+/**
+ * Dual-role device (DRD) work function
+ */

    And here.

+static void usb_drd_work(struct work_struct *work)
+{
+	struct usb_otg *otg = container_of(work, struct usb_otg, work);
+
+	pm_runtime_get_sync(otg->dev);
+	while (drd_statemachine(otg))
+	;

    Indent it more please.

[...]

+/**
+ * start/kick the OTG FSM if we can
+ * fsm->lock must be held
+ */

    Please follow the kernel-doc rules.

[...]

+/**
+ * stop the OTG FSM. Stops Host & Gadget controllers as well.
+ * fsm->lock must be held
+ */

    Likewise.

[...]

+/**
+ * usb_otg_sync_inputs - Sync OTG inputs with the OTG state machine
+ * @fsm:	OTG FSM instance

    Doesn't match the prototype.

+ *
+ * Used by the OTG driver to update the inputs to the OTG
+ * state machine.
+ *
+ * Can be called in IRQ context.
+ */
+void usb_otg_sync_inputs(struct usb_otg *otg)

[...]

+/**
+ * usb_otg_register_gadget - Register the gadget controller to OTG core
+ * @gadget:	gadget controller

    We call that USB device controller (UDC). I'm not sure what you meant here...
    And what about the 2nd arg, 'ops'?

[...]

    IRQ?

+ * @ops: otg to host controller interface
+ * @ops: otg to host controller interface

    Once is enough. :-)

+ * @otg_dev: otg controller device

    OTG?

+/**
+ * struct usb_otg - usb otg controller state
+ *
+ * @default_a: Indicates we are an A device. i.e. Host.
+ * @phy: USB phy interface

    PHY?

+ * @usb_phy: old usb_phy interface
+ * @host: host controller bus
+ * @gadget: gadget device
+ * @state: current otg state
+ * @dev: otg controller device
+ * @caps: otg capabilities revision, hnp, srp, etc
+ * @fsm: otg finite state machine

    OTG?

+ * @hcd_ops: host controller interface
+ * ------- internal use only -------
+ * @primary_hcd: primary host state and interface
+ * @shared_hcd: shared host state and interface
+ * @gadget_ops: gadget controller interface
+ * @list: list of otg controllers
+ * @work: otg state machine work
+ * @wq: otg state machine work queue
+ * @flags: to track if host/gadget is running
+ */
 struct usb_otg {
 	u8			default_a;

[...]

    OTG FSM?

+ * @otg_work: optional custom otg state machine work function

    OTG?

  */

[...]

    Phew, that was a long patch... normally I don't review the patches that 
are such big. :-)

MBR, Sergei