第16章　USB主机、设备与Gadget驱动之USB主机控制器驱动

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最新推荐文章于 2025-07-14 10:03:19 发布 · 2k 阅读

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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))));