第16章 USB主机、设备与Gadget驱动之USB主机控制器驱动

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_driv

评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值