I thought I'd send this around for some comments. This
file is just for some of the folk writing OTG drivers
for their hardware ... normal USB (or Gadget) driver
writers won't need it, only folk twiddling bits in chip
registers to implement HNP and SRP will use this.
It encapsulates what may be called the "OTG Controller":
- Interacts with both the HCD (like ohci-omap) and the UDC
(like omap_udc). It switches the right drivers on at
various times, but doesn't need to know details of how
a given HC or UDC work.
- There could be many implementations, combining ingredients
such as:
* Transceiver ... external, internal, discrete
* Controller ... OMAPs have one on-chip, so does PXA-27x,
these are getting more functional over time
So for example the first implementation of this uses the OMAP
on-chip OTG controller with a Philips ISP1301 transceiver (I2C);
joined at the hip, as it were. This API might well need to
change to handle additional implementations; we'll know when
such implementations start to appear!
What I'll want to do is submit this patch with a minor addition
to usbcore, defining otg_{set,get}_transceiver(), and then
start submitting patches implementing (and using) this. So
please drop a line if you've got any insights about how to
package this kind of functionality, which argue that this is
really the wrong way to go. (Tell us about "improvable" too,
but that'll likely be tricky until I post more code.)
- Dave
// include/linux/usb_otg.h
/*
* These APIs may be used between USB controllers. USB device drivers
* (for either host or peripheral roles) don't use these calls; they
* continue to use just usb_device and usb_gadget.
*/
/* OTG defines lots of enumeration states before device reset */
enum usb_otg_state {
OTG_STATE_UNDEFINED = 0,
/* single-role peripheral, and dual-role default-b */
OTG_STATE_B_IDLE,
OTG_STATE_B_SRP_INIT,
OTG_STATE_B_PERIPHERAL,
/* extra dual-role default-b states */
OTG_STATE_B_WAIT_ACON,
OTG_STATE_B_HOST,
/* dual-role default-a */
OTG_STATE_A_IDLE,
OTG_STATE_A_WAIT_VRISE,
OTG_STATE_A_WAIT_BCON,
OTG_STATE_A_HOST,
OTG_STATE_A_SUSPEND,
OTG_STATE_A_PERIPHERAL,
OTG_STATE_A_WAIT_VFALL,
OTG_STATE_A_VBUS_ERR,
};
/*
* the otg driver needs to interact with both device side and host side
* usb controllers. it decides which controller is active at a given
* moment, using the transciever, ID signal, HNP and sometimes static
* configuration information (including "board isn't wired for otg").
*/
struct otg_transceiver {
struct device *dev;
const char *label;
u8 default_a;
enum usb_otg_state state;
struct usb_bus *host;
struct usb_gadget *gadget;
/* to pass extra port status to the root hub */
u16 port_status;
u16 port_change;
/* bind/unbind the host controller */
int (*set_host)(struct otg_transceiver *otg,
struct usb_bus *host);
/* bind/unbind the peripheral controller */
int (*set_peripheral)(struct otg_transceiver *otg,
struct usb_gadget *gadget);
/* effective for B devices, ignored for A-peripheral */
int (*set_power)(struct otg_transceiver *otg,
unsigned mA);
/* for B devices only: start session with A-Host */
int (*start_srp)(struct otg_transceiver *otg);
/* start or continue HNP role switch */
int (*start_hnp)(struct otg_transceiver *otg);
};
/* for board-specific init logic */
extern int otg_set_transceiver(struct otg_transceiver *);
/* for usb host and peripheral controller drivers */
extern struct otg_transceiver *otg_get_transceiver(void);
static inline int
otg_start_hnp(struct otg_transceiver *otg)
{
return otg->start_hnp(otg);
}
/* for HCDs */
static inline int
otg_set_host(struct otg_transceiver *otg, struct usb_bus *host)
{
return otg->set_host(otg, host);
}
/* for usb peripheral controller drivers */
static inline int
otg_set_peripheral(struct otg_transceiver *otg, struct usb_gadget *periph)
{
return otg->set_peripheral(otg, periph);
}
static inline int
otg_set_power(struct otg_transceiver *otg, unsigned mA)
{
return otg->set_power(otg, mA);
}
static inline int
otg_start_srp(struct otg_transceiver *otg)
{
return otg->start_srp(otg);
}
