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Subject[RFC][PATCH 9/9] usb: otg-fsm: Add documentation for struct otg_fsm
Date
struct otg_fsm is the interface to the OTG state machine.

Document the input, output and internal state variables.
Definations are taken from Table 7-2 and Table 7-4 of
the USB OTG & EH Specification Rev.2.0

Re-arrange some of the members as per use case for more
clarity.

Signed-off-by: Roger Quadros <rogerq@ti.com>
---
include/linux/usb/otg-fsm.h | 76 +++++++++++++++++++++++++++++++++++++++++----
1 file changed, 70 insertions(+), 6 deletions(-)

diff --git a/include/linux/usb/otg-fsm.h b/include/linux/usb/otg-fsm.h
index 176c4fc..10f7a1d 100644
--- a/include/linux/usb/otg-fsm.h
+++ b/include/linux/usb/otg-fsm.h
@@ -57,37 +57,101 @@ enum otg_fsm_timer {
NUM_OTG_FSM_TIMERS,
};

-/* OTG state machine according to the OTG spec */
+/**
+ * struct otg_fsm - OTG state machine according to the OTG spec
+ *
+ * OTG hardware Inputs
+ *
+ * Common inputs for A and B device
+ * @id: TRUE for B-device, FALSE for A-device.
+ * @adp_change: TRUE when current ADP measurement (n) value, compared to the
+ * ADP measurement taken at n-2, differs by more than CADP_THR
+ * @power_up: TRUE when the OTG device first powers up its USB system and
+ * ADP measurement taken if ADP capable
+ *
+ * A-Device state inputs
+ * @a_srp_det: TRUE if the A-device detects SRP
+ * @a_vbus_vld: TRUE when VBUS voltage is in regulation
+ * @b_conn: TRUE if the A-device detects connection from the B-device
+ * @a_bus_resume: TRUE when the B-device detects that the A-device is signaling
+ * a resume (K state)
+ * @a_conn: TRUE if the B-device detects a connection from the A-device
+ * @b_se0_srp: TRUE when the line has been at SE0 for more than the minimum
+ * time before generating SRP
+ * @b_ssend_srp: TRUE when the VBUS has been below VOTG_SESS_VLD for more than
+ * the minimum time before generating SRP
+ * @b_sess_vld: TRUE when the B-device detects that the voltage on VBUS is
+ * above VOTG_SESS_VLD
+ * @test_device: TRUE when the B-device switches to B-Host and detects an OTG test device
+ * FIXME: must be set by host/hub driver
+ *
+ * Application inputs (A-Device)
+ * @a_bus_drop: TRUE when A-device application needs to power down the bus
+ * @a_bus_req: TRUE when A-device application wants to use the bus.
+ * FALSE to suspend the bus
+ *
+ * Application inputs (B-Device)
+ * @b_bus_req: TRUE during the time that the Application running on the
+ * B-device wants to use the bus
+ *
+ * Auxilary inputs
+ * @a_sess_vld: ??
+ * @b_bus_suspend: ??
+ * @b_bus_resume: ??
+ *
+ * OTG Output status. Read only for users. updated by otg_ops() helpers
+ *
+ * Outputs for Both A and B device
+ * @drv_vbus: TRUE when A-device is driving VBUS
+ * @loc_conn: TRUE when the local device has signaled that it is connected to the bus
+ * @loc_sof: TRUE when the local device is generating activity on the bus
+ * @adp_prb: TRUE when the local device is in the process of doing ADP probing
+ *
+ * Outputs for B-device state
+ * @adp_sns: TRUE when the B-device is in the process of carrying out ADP sensing
+ * @data_pulse: TRUE when the B-device is performing data line pulsing
+ *
+ * Internal Variables
+ *
+ * a_set_b_hnp_en: TRUE when the A-device has successfully set the b_hnp_enable bit in the B-device.
+ * FIXME: OTG fsm uses otg->host->b_hnp_enable instead
+ * b_srp_done: TRUE when the B-device has completed initiating SRP
+ * b_hnp_enable: TRUE when the B-device has accepted the SetFeature(b_hnp_enable) B-device
+ * FIXME: OTG fsm uses otg->gadget->b_hnp_enable instead
+ * a_clr_err: Asserted (by application ?) to clear a_vbus_err due to an overcurrent condition
+ * and causes the A-device to transition to a_wait_vfall
+ */
struct otg_fsm {
/* Input */
int id;
int adp_change;
int power_up;
- int test_device;
- int a_bus_drop;
- int a_bus_req;
int a_srp_det;
int a_vbus_vld;
int b_conn;
int a_bus_resume;
int a_bus_suspend;
int a_conn;
- int b_bus_req;
int b_se0_srp;
int b_ssend_srp;
int b_sess_vld;
+ int test_device;
+ int a_bus_drop;
+ int a_bus_req;
+ int b_bus_req;
+
/* Auxilary inputs */
int a_sess_vld;
int b_bus_resume;
int b_bus_suspend;

/* Output */
- int data_pulse;
int drv_vbus;
int loc_conn;
int loc_sof;
int adp_prb;
int adp_sns;
+ int data_pulse;

/* Internal variables */
int a_set_b_hnp_en;
--
2.1.0


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