16.2 USB主机控制器驱动
16.2.1 USB主机控制器驱动的整体结构
USB主机控制器规格：OHCI（Open Host Controller Interface）、UHCI（Universal Host Controller Interface）、EHCI（Enhanced Host Controller Interface）和EHCI（Extensible Host Controller
Interface）。OHCI驱动程序用来为非PC系统上以及带有SiS和ALi芯片组（中国台湾）的PC主板上的USB芯片提供支持。UHCI驱动程序多用来为大多数其他PC主板（包括Intel和Via）上的USB芯片提供支持。EHCI由USB 2.0规范所提出，EHCI兼容于OHCI和UHCI。由于UHCI的硬件线路比OHCI简单，所以成本较低，但需要较复杂的驱动程序，CPU负荷稍重。EHCI，即可扩展的主机控制器接口是Intel公司开发的一个USB主机控制器接口，EHCI主要是面向USB 3.0的，同时EHCI也支持USB 2.0及以下（向后兼容）的设备。
1.主机控制器驱动
在Linux内核中，用usb_hcd结构体描述USB主机控制器驱动，包含USB主机控制器的“家务”信息、硬件资源、状态描述和用于操作主机控制器的hc_driver等，其定义如代码清单16.6所示。
代码清单16.6 usb_hcd结构体
linux/usb/hcd.h
struct usb_hcd {
/*
* housekeeping
*/
struct usb_bus self; /* hcd is-a bus */
struct kref kref; /* reference counter */
const char *product_desc; /* product/vendor string */
int speed; /* Speed for this roothub.
* May be different from
* hcd->driver->flags & HCD_MASK
*/
char irq_descr[24]; /* driver + bus # */
struct timer_list rh_timer; /* drives root-hub polling */
struct urb *status_urb; /* the current status urb */
#ifdef CONFIG_PM_RUNTIME
struct work_struct wakeup_work; /* for remote wakeup */
#endif
/*
* hardware info/state
*/
const struct hc_driver *driver; /* hw-specific hooks */
/*
* OTG and some Host controllers need software interaction with phys;
* other external phys should be software-transparent
*/
struct usb_phy *usb_phy;
struct phy *phy;
/* Flags that need to be manipulated atomically because they can
* change while the host controller is running. Always use
* set_bit() or clear_bit() to change their values.
*/
unsigned long flags;
#define HCD_FLAG_HW_ACCESSIBLE 0 /* at full power */
#define HCD_FLAG_POLL_RH 2 /* poll for rh status? */
#define HCD_FLAG_POLL_PENDING 3 /* status has changed? */
#define HCD_FLAG_WAKEUP_PENDING 4 /* root hub is resuming? */
#define HCD_FLAG_RH_RUNNING 5 /* root hub is running? */
#define HCD_FLAG_DEAD 6 /* controller has died? */
/* The flags can be tested using these macros; they are likely to
* be slightly faster than test_bit().
*/
#define HCD_HW_ACCESSIBLE(hcd) ((hcd)->flags & (1U << HCD_FLAG_HW_ACCESSIBLE))
#define HCD_POLL_RH(hcd) ((hcd)->flags & (1U << HCD_FLAG_POLL_RH))
#define HCD_POLL_PENDING(hcd) ((hcd)->flags & (1U << HCD_FLAG_POLL_PENDING))
#define HCD_WAKEUP_PENDING(hcd) ((hcd)->flags & (1U << HCD_FLAG_WAKEUP_PENDING))
#define HCD_RH_RUNNING(hcd) ((hcd)->flags & (1U << HCD_FLAG_RH_RUNNING))
#define HCD_DEAD(hcd) ((hcd)->flags & (1U << HCD_FLAG_DEAD))
/* Flags that get set only during HCD registration or removal. */
unsigned rh_registered:1;/* is root hub registered? */
unsigned rh_pollable:1; /* may we poll the root hub? */
unsigned msix_enabled:1; /* driver has MSI-X enabled? */
unsigned remove_phy:1; /* auto-remove USB phy */
/* The next flag is a stopgap, to be removed when all the HCDs
* support the new root-hub polling mechanism. */
unsigned uses_new_polling:1;
unsigned wireless:1; /* Wireless USB HCD */
unsigned authorized_default:1;
unsigned has_tt:1; /* Integrated TT in root hub */
unsigned amd_resume_bug:1; /* AMD remote wakeup quirk */
unsigned can_do_streams:1; /* HC supports streams */
unsigned tpl_support:1; /* OTG & EH TPL support */
unsigned cant_recv_wakeups:1;
/* wakeup requests from downstream aren't received */
unsigned int irq; /* irq allocated */
void __iomem *regs; /* device memory/io */
resource_size_t rsrc_start; /* memory/io resource start */
resource_size_t rsrc_len; /* memory/io resource length */
unsigned power_budget; /* in mA, 0 = no limit */
struct giveback_urb_bh high_prio_bh;
struct giveback_urb_bh low_prio_bh;
/* bandwidth_mutex should be taken before adding or removing
* any new bus bandwidth constraints:
* 1. Before adding a configuration for a new device.
* 2. Before removing the configuration to put the device into
* the addressed state.
* 3. Before selecting a different configuration.
* 4. Before selecting an alternate interface setting.
*
* bandwidth_mutex should be dropped after a successful control message
* to the device, or resetting the bandwidth after a failed attempt.
*/
struct mutex *bandwidth_mutex;
struct usb_hcd *shared_hcd;
struct usb_hcd *primary_hcd;
#define HCD_BUFFER_POOLS 4
struct dma_pool *pool[HCD_BUFFER_POOLS];
int state;
# define __ACTIVE 0x01
# define __SUSPEND 0x04
# define __TRANSIENT 0x80
# define HC_STATE_HALT 0
# define HC_STATE_RUNNING (__ACTIVE)
# define HC_STATE_QUIESCING (__SUSPEND|__TRANSIENT|__ACTIVE)
# define HC_STATE_RESUMING (__SUSPEND|__TRANSIENT)
# define HC_STATE_SUSPENDED (__SUSPEND)
#define HC_IS_RUNNING(state) ((state) & __ACTIVE)
#define HC_IS_SUSPENDED(state) ((state) & __SUSPEND)
/* more shared queuing code would be good; it should support
* smarter scheduling, handle transaction translators, etc;
* input size of periodic table to an interrupt scheduler.
* (ohci 32, uhci 1024, ehci 256/512/1024).
*/
/* The HC driver's private data is stored at the end of
* this structure.
*/
unsigned long hcd_priv[0]
__attribute__ ((aligned(sizeof(s64))));
};
usb_hcd结构体中的hc_driver成员非常重要，hc_driver包含具体的用于操作主机控制器的钩子函数，即
“hw-specific hooks”，其定义如代码清单16.7所示。
代码清单16.7 hc_driver结构体
linux/usb/hcd.h
struct hc_driver {
const char *description; /* "ehci-hcd" etc */
const char *product_desc; /* product/vendor string */
size_t hcd_priv_size; /* size of private data */
/* irq handler */
irqreturn_t (*irq) (struct usb_hcd *hcd);
int flags;
#define HCD_MEMORY 0x0001 /* HC regs use memory (else I/O) */
#define HCD_LOCAL_MEM 0x0002 /* HC needs local memory */
#define HCD_SHARED 0x0004 /* Two (or more) usb_hcds share HW */
#define HCD_RT_OLD_ENUM 0x0008 /* HC supports short enumeration
on root port */
#define HCD_USB11 0x0010 /* USB 1.1 */
#define HCD_USB2 0x0020 /* USB 2.0 */
#define HCD_USB25 0x0030 /* Wireless USB 1.0 (USB 2.5)*/
#define HCD_USB3 0x0040 /* USB 3.0 */
#define HCD_MASK 0x0070
#define HCD_BH 0x0100 /* URB complete in BH context */
/* called to init HCD and root hub */
int (*reset) (struct usb_hcd *hcd);
int (*start) (struct usb_hcd *hcd);
/* NOTE: these suspend/resume calls relate to the HC as
* a whole, not just the root hub; they're for PCI bus glue.
*/
/* called after suspending the hub, before entering D3 etc */
int (*pci_suspend)(struct usb_hcd *hcd, bool do_wakeup);
/* called after entering D0 (etc), before resuming the hub */
int (*pci_resume)(struct usb_hcd *hcd, bool hibernated);
/* cleanly make HCD stop writing memory and doing I/O */
void (*stop) (struct usb_hcd *hcd);
/* shutdown HCD */
void (*shutdown) (struct usb_hcd *hcd);
/* return current frame number */
int (*get_frame_number) (struct usb_hcd *hcd);
/* manage i/o requests, device state */
int (*urb_enqueue)(struct usb_hcd *hcd,
struct urb *urb, gfp_t mem_flags);
int (*urb_dequeue)(struct usb_hcd *hcd,
struct urb *urb, int status);
/*
* (optional) these hooks allow an HCD to override the default DMA
* mapping and unmapping routines. In general, they shouldn't be
* necessary unless the host controller has special DMA requirements,
* such as alignment contraints. If these are not specified, the
* general usb_hcd_(un)?map_urb_for_dma functions will be used instead
* (and it may be a good idea to call these functions in your HCD
* implementation)
*/
int (*map_urb_for_dma)(struct usb_hcd *hcd, struct urb *urb,
gfp_t mem_flags);
void (*unmap_urb_for_dma)(struct usb_hcd *hcd, struct urb *urb);
/* hw synch, freeing endpoint resources that urb_dequeue can't */
void (*endpoint_disable)(struct usb_hcd *hcd,
struct usb_host_endpoint *ep);
/* (optional) reset any endpoint state such as sequence number
and current window */
void (*endpoint_reset)(struct usb_hcd *hcd, struct usb_host_endpoint *ep);
/* root hub support */
int (*hub_status_data) (struct usb_hcd *hcd, char *buf);
int (*hub_control) (struct usb_hcd *hcd,
u16 typeReq, u16 wValue, u16 wIndex,
char *buf, u16 wLength);
int (*bus_suspend)(struct usb_hcd *);
int (*bus_resume)(struct usb_hcd *);
int (*start_port_reset)(struct usb_hcd *, unsigned port_num);
/* force handover of high-speed port to full-speed companion */
void (*relinquish_port)(struct usb_hcd *, int);
/* has a port been handed over to a companion? */
int (*port_handed_over)(struct usb_hcd *, int);
/* CLEAR_TT_BUFFER completion callback */
void (*clear_tt_buffer_complete)(struct usb_hcd *, struct usb_host_endpoint *);
/* xHCI specific functions */
/* Called by usb_alloc_dev to alloc HC device structures */
int (*alloc_dev)(struct usb_hcd *, struct usb_device *);
/* Called by usb_disconnect to free HC device structures */
void (*free_dev)(struct usb_hcd *, struct usb_device *);
/* Change a group of bulk endpoints to support multiple stream IDs */
int (*alloc_streams)(struct usb_hcd *hcd, struct usb_device *udev,
struct usb_host_endpoint **eps, unsigned int num_eps,
unsigned int num_streams, gfp_t mem_flags);
/* Reverts a group of bulk endpoints back to not using stream IDs.
* Can fail if we run out of memory.
*/
int (*free_streams)(struct usb_hcd *hcd, struct usb_device *udev,
struct usb_host_endpoint **eps, unsigned int num_eps,
gfp_t mem_flags);
/* Bandwidth computation functions */
/* Note that add_endpoint() can only be called once per endpoint before
* check_bandwidth() or reset_bandwidth() must be called.
* drop_endpoint() can only be called once per endpoint also.
* A call to xhci_drop_endpoint() followed by a call to
* xhci_add_endpoint() will add the endpoint to the schedule with
* possibly new parameters denoted by a different endpoint descriptor
* in usb_host_endpoint. A call to xhci_add_endpoint() followed by a
* call to xhci_drop_endpoint() is not allowed.
*/
/* Allocate endpoint resources and add them to a new schedule */
int (*add_endpoint)(struct usb_hcd *, struct usb_device *,
struct usb_host_endpoint *);
/* Drop an endpoint from a new schedule */
int (*drop_endpoint)(struct usb_hcd *, struct usb_device *,
struct usb_host_endpoint *);
/* Check that a new hardware configuration, set using
* endpoint_enable and endpoint_disable, does not exceed bus
* bandwidth. This must be called before any set configuration
* or set interface requests are sent to the device.
*/
int (*check_bandwidth)(struct usb_hcd *, struct usb_device *);
/* Reset the device schedule to the last known good schedule,
* which was set from a previous successful call to
* check_bandwidth(). This reverts any add_endpoint() and
* drop_endpoint() calls since that last successful call.
* Used for when a check_bandwidth() call fails due to resource
* or bandwidth constraints.
*/
void (*reset_bandwidth)(struct usb_hcd *, struct usb_device *);
/* Returns the hardware-chosen device address */
int (*address_device)(struct usb_hcd *, struct usb_device *udev);
/* prepares the hardware to send commands to the device */
int (*enable_device)(struct usb_hcd *, struct usb_device *udev);
/* Notifies the HCD after a hub descriptor is fetched.
* Will block.
*/
int (*update_hub_device)(struct usb_hcd *, struct usb_device *hdev,
struct usb_tt *tt, gfp_t mem_flags);
int (*reset_device)(struct usb_hcd *, struct usb_device *);
/* Notifies the HCD after a device is connected and its
* address is set
*/
int (*update_device)(struct usb_hcd *, struct usb_device *);
int (*set_usb2_hw_lpm)(struct usb_hcd *, struct usb_device *, int);
/* USB 3.0 Link Power Management */
/* Returns the USB3 hub-encoded value for the U1/U2 timeout. */
int (*enable_usb3_lpm_timeout)(struct usb_hcd *,
struct usb_device *, enum usb3_link_state state);
/* The xHCI host controller can still fail the command to
* disable the LPM timeouts, so this can return an error code.
*/
int (*disable_usb3_lpm_timeout)(struct usb_hcd *,
struct usb_device *, enum usb3_link_state state);
int (*find_raw_port_number)(struct usb_hcd *, int);
void (*log_urb)(struct urb *urb, char *event, unsigned extra);
void (*dump_regs)(struct usb_hcd *);
void (*set_autosuspend_delay)(struct usb_device *);
void (*reset_sof_bug_handler)(struct usb_hcd *hcd, u32 val);
};
备注：
在Linux内核中，使用如下函数来创建HCD：
linux/usb/hcd.h
extern struct usb_hcd *usb_create_hcd(const struct hc_driver *driver,
struct device *dev, const char *bus_name);
drivers/usb/core/hcd.c
/**
* usb_create_shared_hcd - create and initialize an HCD structure
* @driver: HC driver that will use this hcd
* @dev: device for this HC, stored in hcd->self.controller
* @bus_name: value to store in hcd->self.bus_name
* @primary_hcd: a pointer to the usb_hcd structure that is sharing the
* PCI device. Only allocate certain resources for the primary HCD
* Context: !in_interrupt()
*
* Allocate a struct usb_hcd, with extra space at the end for the
* HC driver's private data. Initialize the generic members of the
* hcd structure.
*
* Return: On success, a pointer to the created and initialized HCD structure.
* On failure (e.g. if memory is unavailable), %NULL.
*/
struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver,
struct device *dev, const char *bus_name,
struct usb_hcd *primary_hcd)
{
struct usb_hcd *hcd;
hcd = kzalloc(sizeof(*hcd) + driver->hcd_priv_size, GFP_KERNEL);
if (!hcd) {
dev_dbg (dev, "hcd alloc failed\n");
return NULL;
}
if (primary_hcd == NULL) {
hcd->bandwidth_mutex = kmalloc(sizeof(*hcd->bandwidth_mutex),
GFP_KERNEL);
if (!hcd->bandwidth_mutex) {
kfree(hcd);
dev_dbg(dev, "hcd bandwidth mutex alloc failed\n");
return NULL;
}
mutex_init(hcd->bandwidth_mutex);
dev_set_drvdata(dev, hcd);
} else {
mutex_lock(&usb_port_peer_mutex);
hcd->bandwidth_mutex = primary_hcd->bandwidth_mutex;
hcd->primary_hcd = primary_hcd;
primary_hcd->primary_hcd = primary_hcd;
hcd->shared_hcd = primary_hcd;
primary_hcd->shared_hcd = hcd;
mutex_unlock(&usb_port_peer_mutex);
}
kref_init(&hcd->kref);
usb_bus_init(&hcd->self);
hcd->self.controller = dev;
hcd->self.bus_name = bus_name;
hcd->self.uses_dma = (dev->dma_mask != NULL);
init_timer(&hcd->rh_timer);
hcd->rh_timer.function = rh_timer_func;
hcd->rh_timer.data = (unsigned long) hcd;
#ifdef CONFIG_PM_RUNTIME
INIT_WORK(&hcd->wakeup_work, hcd_resume_work);
#endif
hcd->driver = driver;
hcd->speed = driver->flags & HCD_MASK;
hcd->product_desc = (driver->product_desc) ? driver->product_desc :
"USB Host Controller";
return hcd;
}
EXPORT_SYMBOL_GPL(usb_create_shared_hcd);
/**
* usb_create_hcd - create and initialize an HCD structure
* @driver: HC driver that will use this hcd
* @dev: device for this HC, stored in hcd->self.controller
* @bus_name: value to store in hcd->self.bus_name
* Context: !in_interrupt()
*
* Allocate a struct usb_hcd, with extra space at the end for the
* HC driver's private data. Initialize the generic members of the
* hcd structure.
*
* Return: On success, a pointer to the created and initialized HCD
* structure. On failure (e.g. if memory is unavailable), %NULL.
*/
struct usb_hcd *usb_create_hcd(const struct hc_driver *driver,
struct device *dev, const char *bus_name)
{
return usb_create_shared_hcd(driver, dev, bus_name, NULL);
}
EXPORT_SYMBOL_GPL(usb_create_hcd);
如下函数被用来增加和移除HCD：
linux/usb/hcd.h
extern int usb_add_hcd(struct usb_hcd *hcd,
unsigned int irqnum, unsigned long irqflags);
extern void usb_remove_hcd(struct usb_hcd *hcd);
通过分析代码如下：
结构体struct hc_driver中的urb_enqueue（）非常重要，实际上，上层通过usb_submit_urb（）提交1个USB请求后，该函数调用usb_hcd_submit_urb（），并最终调用至usb_hcd的driver成员（hc_driver类型）的urb_enqueue（）函数。
2.EHCI主机控制器驱动
EHCI HCD驱动属于HCD驱动的实例，EHCI HCD驱动定义了一个ehci_hcd结构体，通常作为usb_hcd结构体的的私有数据（hcd_priv），如代码清单16.8所示。
代码清单16.8 ehci_hcd结构体
drivers/usb/host/ehci.h
struct ehci_hcd { /* one per controller */
/* timing support */
enum ehci_hrtimer_event next_hrtimer_event;
unsigned enabled_hrtimer_events;
ktime_t hr_timeouts[EHCI_HRTIMER_NUM_EVENTS];
struct hrtimer hrtimer;
int PSS_poll_count;
int ASS_poll_count;
int died_poll_count;
/* glue to PCI and HCD framework */
struct ehci_caps __iomem *caps;
struct ehci_regs __iomem *regs;
struct ehci_dbg_port __iomem *debug;
__u32 hcs_params; /* cached register copy */
spinlock_t lock;
enum ehci_rh_state rh_state;
/* general schedule support */
bool scanning:1;
bool need_rescan:1;
bool intr_unlinking:1;
bool iaa_in_progress:1;
bool async_unlinking:1;
bool shutdown:1;
struct ehci_qh *qh_scan_next;
/* async schedule support */
struct ehci_qh *async;
struct ehci_qh *dummy; /* For AMD quirk use */
struct list_head async_unlink;
struct list_head async_idle;
unsigned async_unlink_cycle;
unsigned async_count; /* async activity count */
/* periodic schedule support */
#define DEFAULT_I_TDPS 1024 /* some HCs can do less */
unsigned periodic_size;
__hc32 *periodic; /* hw periodic table */
dma_addr_t periodic_dma;
struct list_head intr_qh_list;
unsigned i_thresh; /* uframes HC might cache */
union ehci_shadow *pshadow; /* mirror hw periodic table */
struct list_head intr_unlink_wait;
struct list_head intr_unlink;
unsigned intr_unlink_wait_cycle;
unsigned intr_unlink_cycle;
unsigned now_frame; /* frame from HC hardware */
unsigned last_iso_frame; /* last frame scanned for iso */
unsigned intr_count; /* intr activity count */
unsigned isoc_count; /* isoc activity count */
unsigned periodic_count; /* periodic activity count */
unsigned uframe_periodic_max; /* max periodic time per uframe */
/* list of itds & sitds completed while now_frame was still active */
struct list_head cached_itd_list;
struct ehci_itd *last_itd_to_free;
struct list_head cached_sitd_list;
struct ehci_sitd *last_sitd_to_free;
/* per root hub port */
unsigned long reset_done [EHCI_MAX_ROOT_PORTS];
/* bit vectors (one bit per port) */
unsigned long bus_suspended; /* which ports were
already suspended at the start of a bus suspend */
unsigned long companion_ports; /* which ports are
dedicated to the companion controller */
unsigned long owned_ports; /* which ports are
owned by the companion during a bus suspend */
unsigned long port_c_suspend; /* which ports have
the change-suspend feature turned on */
unsigned long suspended_ports; /* which ports are
suspended */
unsigned long resuming_ports; /* which ports have
started to resume */
/* per-HC memory pools (could be per-bus, but ...) */
struct dma_pool *qh_pool; /* qh per active urb */
struct dma_pool *qtd_pool; /* one or more per qh */
struct dma_pool *itd_pool; /* itd per iso urb */
struct dma_pool *sitd_pool; /* sitd per split iso urb */
unsigned random_frame;
unsigned long next_statechange;
ktime_t last_periodic_enable;
u32 command;
unsigned log2_irq_thresh;
/* SILICON QUIRKS */
unsigned no_selective_suspend:1;
unsigned has_fsl_port_bug:1; /* FreeScale */
unsigned big_endian_mmio:1;
unsigned big_endian_desc:1;
unsigned big_endian_capbase:1;
unsigned has_amcc_usb23:1;
unsigned need_io_watchdog:1;
unsigned amd_pll_fix:1;
unsigned use_dummy_qh:1; /* AMD Frame List table quirk*/
unsigned has_synopsys_hc_bug:1; /* Synopsys HC */
unsigned frame_index_bug:1; /* MosChip (AKA NetMos) */
unsigned need_oc_pp_cycle:1; /* MPC834X port power */
unsigned susp_sof_bug:1; /*Chip Idea HC*/
unsigned resume_sof_bug:1;/*Chip Idea HC*/
unsigned reset_sof_bug:1; /*Chip Idea HC*/
bool disable_cerr;
u32 reset_delay;
bool no_testmode_suspend; /* MSM Chipidea HC */
unsigned imx28_write_fix:1; /* For Freescale i.MX28 */
/* required for usb32 quirk */
#define OHCI_CTRL_HCFS (3 << 6)
#define OHCI_USB_OPER (2 << 6)
#define OHCI_USB_SUSPEND (3 << 6)
#define OHCI_HCCTRL_OFFSET 0x4
#define OHCI_HCCTRL_LEN 0x4
__hc32 *ohci_hcctrl_reg;
unsigned has_hostpc:1;
unsigned has_tdi_phy_lpm:1;
unsigned has_ppcd:1; /* support per-port change bits */
unsigned pool_64_bit_align:1; /* for 64 bit alignment */
u8 sbrn; /* packed release number */
/* irq statistics */
#ifdef EHCI_STATS
struct ehci_stats stats;
# define COUNT(x) do { (x)++; } while (0)
#else
# define COUNT(x) do {} while (0)
#endif
/* debug files */
#ifdef CONFIG_DYNAMIC_DEBUG
struct dentry *debug_dir;
#endif
/* bandwidth usage */
#define EHCI_BANDWIDTH_SIZE 64
#define EHCI_BANDWIDTH_FRAMES (EHCI_BANDWIDTH_SIZE >> 3)
u8 bandwidth[EHCI_BANDWIDTH_SIZE];
/* us allocated per uframe */
u8 tt_budget[EHCI_BANDWIDTH_SIZE];
/* us budgeted per uframe */
struct list_head tt_list;
/* platform-specific data -- must come last */
unsigned long priv[0] __aligned(sizeof(s64));
};
使用如下内联函数可实现usb_hcd和ehci_hcd的相互转换：
drivers/usb/host/ehci.h
/* convert between an HCD pointer and the corresponding EHCI_HCD */
static inline struct ehci_hcd *hcd_to_ehci (struct usb_hcd *hcd)
{
return (struct ehci_hcd *) (hcd->hcd_priv);//从usb_hcd得到ehci_hcd只是取得“私有”数据
}
static inline struct usb_hcd *ehci_to_hcd (struct ehci_hcd *ehci)
{
/* 从ehci_hcd得到usb_hcd则是通过宏container_of（）从结构体成员获得结构体指针 */
}
使用如下函数可初始化EHCI主机控制器：
drivers/usb/host/ehci-hcd.c
static int ehci_init(struct usb_hcd *hcd);
如下函数分别用于开启、停止及复位EHCI控制器：
drivers/usb/host/ehci-hcd.c
static int ehci_run (struct usb_hcd *hcd);
static void ehci_stop (struct usb_hcd *hcd);
static int ehci_reset (struct ehci_hcd *ehci);
上述函数在drivers/usb/host/ehci-hcd.c文件中被填充给了一个hc_driver结构体的generic的实例ehci_hc_driver。
static const struct hc_driver ehci_hc_driver = {
.description = hcd_name,
.product_desc = "EHCI Host Controller",
.hcd_priv_size = sizeof(struct ehci_hcd),
/*
* generic hardware linkage
*/
.irq = ehci_irq,
.flags = HCD_MEMORY | HCD_USB2 | HCD_BH,
/*
* basic lifecycle operations
*/
.reset = ehci_setup,
.start = ehci_run,
.stop = ehci_stop,
.shutdown = ehci_shutdown,
/*
* managing i/o requests and associated device resources
*/
.urb_enqueue = ehci_urb_enqueue,
.urb_dequeue = ehci_urb_dequeue,
.endpoint_disable = ehci_endpoint_disable,
.endpoint_reset = ehci_endpoint_reset,
.clear_tt_buffer_complete = ehci_clear_tt_buffer_complete,
/*
* scheduling support
*/
.get_frame_number = ehci_get_frame,
/*
* root hub support
*/
.hub_status_data = ehci_hub_status_data,
.hub_control = ehci_hub_control,
.bus_suspend = ehci_bus_suspend,
.bus_resume = ehci_bus_resume,
.relinquish_port = ehci_relinquish_port,
.port_handed_over = ehci_port_handed_over,
/*
* device support
*/
.free_dev = ehci_remove_device,
};
drivers/usb/host/ehci-hcd.c实现绝大多数EHCI主机驱动的工作，具体的EHCI实例简单地调用如下函数：
void ehci_init_driver(struct hc_driver *drv, const struct ehci_driver_overrides *over)
初始化hc_driver即可，这个函数会被generic的ehci_hc_driver实例复制给每个具体底层驱动的实例，当然底
层驱动可以通过第2个参数，即ehci_driver_overrides重写中间层的reset（）、port_power（）这2个函数，另
外也可以填充一些额外的私有数据，从代码清单16.9ehci_init_driver（）的实现中可以看出。
代码清单16.9 ehci_init_driver的实现
drivers/usb/host/ehci-hcd.c
void ehci_init_driver(struct hc_driver *drv,
const struct ehci_driver_overrides *over)
{
/* Copy the generic table to drv and then apply the overrides */
*drv = ehci_hc_driver;
if (over) {
drv->hcd_priv_size += over->extra_priv_size;
if (over->flags)
drv->flags = over->flags;
if (over->reset)
drv->reset = over->reset;
if (over->bus_suspend)
drv->bus_suspend = over->bus_suspend;
if (over->bus_resume)
drv->bus_resume = over->bus_resume;
}
}
EXPORT_SYMBOL_GPL(ehci_init_driver);
drivers/usb/host/ehci.h
ehci_driver_overrides结构体定义如下：
struct ehci_driver_overrides {
size_t extra_priv_size;
int flags;
int (*reset)(struct usb_hcd *hcd);
irqreturn_t (*irq) (struct usb_hcd *hcd);
int (*urb_enqueue)(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags);
int (*bus_suspend)(struct usb_hcd *);
int (*bus_resume)(struct usb_hcd *);
};
16.2.2 实例：Chipidea USB主机驱动
Chipidea是全球领先的无线、数字消费电子和连接市场模拟和混合信号 IP 独立供应商。Chipidea的USB IP在嵌入式系统中应用比较广泛，其驱动位于drivers/usb/chipidea/目录下。
Chipidea USB驱动的内核代码drivers/usb/chipidea/core.c中的ci_hdrc_probe（）被执行后（即一个
platform_device与ci_hdrc_driver这个platform_driver匹配上），ci_hdrc_probe（）会调用drivers/usb/chipidea/host.c中的ci_hdrc_host_init（）函数，该函数完成hc_driver的初始化并赋值一系列与Chipidea平台相关的私有数据，如代码清单16.10所示。
代码清单16.10 Chipidea USB host驱动初始化
drivers/usb/chipidea/core.c
static int ci_hdrc_probe(struct platform_device *pdev)
{
......
/* initialize role(s) before the interrupt is requested */
if (dr_mode == USB_DR_MODE_OTG || dr_mode == USB_DR_MODE_HOST) {
ret = ci_hdrc_host_init(ci);
if (ret)
dev_info(dev, "doesn't support host\n");
}
......
}
static int ci_hdrc_remove(struct platform_device *pdev)
{
struct ci_hdrc *ci = platform_get_drvdata(pdev);
dbg_remove_files(ci);
free_irq(ci->irq, ci);
ci_role_destroy(ci);
ci_hdrc_enter_lpm(ci, true);
usb_phy_shutdown(ci->transceiver);
return 0;
}
static struct platform_driver ci_hdrc_driver = {
.probe = ci_hdrc_probe,
.remove = ci_hdrc_remove,
.driver = {
.name = "ci_hdrc",
.owner = THIS_MODULE,
},
};
module_platform_driver(ci_hdrc_driver);
drivers/usb/chipidea/host.c
int ci_hdrc_host_init(struct ci_hdrc *ci)
{
struct ci_role_driver *rdrv;
if (!hw_read(ci, CAP_DCCPARAMS, DCCPARAMS_HC))
return -ENXIO;
return -ENOMEM;
rdrv->start = host_start;
rdrv->stop = host_stop;
rdrv->irq = host_irq;
rdrv->name = "host";
ci->roles[CI_ROLE_HOST] = rdrv;
ehci_init_driver(&ci_ehci_hc_driver, NULL);
return 0;
}
usb/host/ehci-hcd.c
void ehci_init_driver(struct hc_driver *drv, const struct ehci_driver_overrides *over)
{
/* Copy the generic table to drv and then apply the overrides */
*drv = ehci_hc_driver;
if (over) {
drv->hcd_priv_size += over->extra_priv_size;
if (over->flags)
drv->flags = over->flags;
if (over->reset)
drv->reset = over->reset;
if (over->bus_suspend)
drv->bus_suspend = over->bus_suspend;
if (over->bus_resume)
drv->bus_resume = over->bus_resume;
}
}
EXPORT_SYMBOL_GPL(ehci_init_driver);