usb驱动学习笔记

1. usb-storage 驱动注册过程.  module_init(usb_stor_init);

usb_stor_init(void) <drivers/usb/storage/usb.c>
    usb_register(&usb_storage_driver);
        usb_register_driver(driver, THIS_MODULE, KBUILD_MODNAME);
            driver_register(&new_driver->drvwrap.driver);
                driver_find(drv->name, drv->bus);
                bus_add_driver(drv);
                    kobject_init_and_add
                    driver_attach(drv);
                        bus_for_each_dev
                            __driver_attach
                                driver_probe_device(drv, dev);
                                    really_probe(dev, drv);
                                        drv->probe(dev);
                kobject_uevent(&priv->kobj, KOBJ_ADD);

2. storage_probe 函数的处理过程.

 

在 usb-stroage 驱动程序注册的过程中, 由于 bus_usb_type 没有定义 probe 函数,所以会执行代码 usb_storage_driver 中定义的 probe 函数.

 

storage_probe(struct usb_interface *intf, const struct usb_device_id *id)
    usb_stor_probe1(&us, intf, id, (id - usb_storage_usb_ids) + us_unusual_dev_list);
        scsi_host_alloc(&usb_stor_host_template, sizeof(*us)); //alloc us->host
        associate_dev(us, intf);
            interface_to_usbdev(intf);
            usb_set_intfdata(intf, us);
            usb_buffer_alloc(us->pusb_dev, sizeof(*us->cr),    GFP_KERNEL, &us->cr_dma); //set us->cr
            usb_buffer_alloc(us->pusb_dev, US_IOBUF_SIZE, GFP_KERNEL, &us->iobuf_dma);//set us->iobuf
        get_device_info(us, id, unusual_dev);
        get_transport(us); //set us->transport = usb_stor_CB_transport; us->transport_reset = usb_stor_CB_reset;
        get_protocol(us); //set us->proto_handler = usb_stor_transparent_scsi_command;
    usb_stor_probe2(us);
        get_pipes(us); //get bulk in/out endpoint.and get contrl in/out endpoint.
        usb_stor_acquire_resources(us); //Acquire all the other resources and add the host
            usb_alloc_urb(0, GFP_KERNEL); //set us->current_urb.
            kthread_run(usb_stor_control_thread, us, "usb-storage"); //set to us->ctl_thread. struct task_struct.sleep at the beginning.
        scsi_add_host(us_to_host(us), &us->pusb_intf->dev);//add us->host into scsi-core.
        kthread_create(usb_stor_scan_thread, us, "usb-stor-scan"); //Start up the thread for delayed SCSI-device scanning
        wake_up_process(th); // wake up kthread usb_stor_scan_thread, which create above.
            set_freezable(); // usb_stor_scan_thread run as below flow. begin this line.
            usb_stor_Bulk_max_lun(us); //set us->max_lun. lun<logical unit number>
                usb_stor_control_msg(...); //args doesn't show as too long.
                    usb_fill_control_urb(...); //fill urb with args.
                    usb_stor_msg_common(us, timeout);
                        init_completion(&urb_done);
                        usb_submit_urb(us->current_urb, GFP_NOIO); //submit urb to the usb-core.
                        wait_for_completion_interruptible_timeout(...);//wait urb to be done.
            scsi_scan_host(us_to_host(us));

3. usb_stor_host_template 数据结构.

 

struct scsi_host_template usb_stor_host_template = {
    .name =                "usb-storage",
    .proc_name =            "usb-storage",
    .proc_info =            proc_info,
    .info =                host_info,
    .queuecommand =            queuecommand, //called by scsi_dispatch_cmd() in scsi.c, dispatch srb.
    .eh_abort_handler =        command_abort, //abort command.
    .eh_device_reset_handler =    device_reset, //reset device.
    .eh_bus_reset_handler =        bus_reset, //reset all, include usb scsi host, bus, driver.
    .can_queue =            1,
    .cmd_per_lun =            1,
    .this_id =            -1,
    .slave_alloc =            slave_alloc,
    .slave_configure =        slave_configure,
    .sg_tablesize =            SG_ALL,
    .max_sectors = 240,
    .use_clustering =        1,
    .emulated =            1,
    .skip_settle_delay =        1,
    .sdev_attrs =            sysfs_device_attr_list,
    .module =            THIS_MODULE
}

 

4. usb_storage_driver 数据结构.

 

usb-storage 驱动的核心结构.

static struct usb_driver usb_storage_driver = {
    .name =        "usb-storage",
    .probe =    storage_probe, //注册驱动或者有设备插入时被调用.
    .disconnect =    usb_stor_disconnect,//移除设备或者移除驱动时调用.
    .suspend =    usb_stor_suspend, //系统挂起时调用
    .resume =    usb_stor_resume, //系统从挂起恢复执行时调用.
    .reset_resume =    usb_stor_reset_resume,//系统从挂起恢复执行时,用reset替代resume.
    .pre_reset =    usb_stor_pre_reset, //USB设备reset之前调用.
    .post_reset =    usb_stor_post_reset,//USB设备reset之后调用.
    .id_table =    usb_storage_usb_ids,
    .soft_unbind =    1,
};

 

5. USB 读写.

 

(1) 当用户需要访问 USB 设备时, scsi-core 会调用 scsi_dispatch_cmd(), 而 scsi_dispatch_cmd()
会进一步调用 scsi_host_template 中的 queuecommand, 也就是 usb_stor_host_template 中的 queuecommand() 函数.

queuecommand(struct scsi_cmnd *srb,    void (*done)(struct scsi_cmnd *))
    host_to_us(srb->device->host) //get us.
    complete(&us->cmnd_ready); //this would wake up usb-storage kthread, execute func usb_stor_control_thread.

(2) usb_stor_control_thread 线程的处理过程.

usb_stor_control_thread(void * __us)
    if (wait_for_completion_interruptible(&us->cmnd_ready)) //wake up by queuecommand(). see 4 lines above.
    us->proto_handler(us->srb, us); //see storage_probe() -> get_protocol(us). called usb_stor_transparent_scsi_command actually.
    us->srb->scsi_done(us->srb); //transfer already done.

(3) usb_stor_transparent_scsi_command() 函数的处理过程.
USB 的数据传输分为三个过程: 命令传输, 数据传输, 状态传输.

usb_stor_transparent_scsi_command(struct scsi_cmnd *srb, struct us_data *us)
    usb_stor_invoke_transport(srb, us); //send the command to the transport layer
        scsi_set_resid(srb, 0);
        us->transport(srb, us); //see storage_probe() -> get_transport(us), called usb_stor_CB_transport() acctually.
        usb_stor_ctrl_transfer(...); //send command.
            usb_fill_control_urb(...); //fill urb with args.
            usb_stor_msg_common(us, 0); //submit urb.
                init_completion(&urb_done);
                usb_submit_urb(us->current_urb, GFP_NOIO); //submit urb to the usb-core.
                wait_for_completion_interruptible_timeout(...);//wait urb to be done.
            interpret_urb_result(...); //translate result of usb_stor_msg_common().
        usb_stor_bulk_srb(us, pipe, srb); //transfer data.
            usb_stor_bulk_transfer_sglist(...); //use scatter/gather.
                usb_sg_init(...); //init scatter/gather.
                usb_sg_wait(&us->current_sg); //wait for the completion of the transfer .
                interpret_urb_result(...);
            scsi_set_resid(srb, scsi_bufflen(srb) - partial);
        usb_stor_intr_transfer(us, us->iobuf, 2);// get transfer status.
            usb_fill_int_urb(...);
            usb_stor_msg_common(us, 0);
            interpret_urb_result(...);

6. 移除 USB 设备. usb_stor_disconnect() 函数的处理过程. 基本都是释放资源, 释放锁.

 

 

usb_stor_disconnect(struct usb_interface *intf)
    usb_get_intfdata(intf); // get usb-data.
    quiesce_and_remove_host(us);
        wake_up(&us->delay_wait);
        wait_for_completion(&us->scanning_done);
        scsi_remove_host(host);
        wake_up(&us->delay_wait);
    release_everything(us);
        usb_stor_release_resources(us);
            complete(&us->cmnd_ready);
            kthread_stop(us->ctl_thread);
            kfree(us->extra);
            usb_free_urb(us->current_urb);
        dissociate_dev(us);
            usb_buffer_free(us->pusb_dev, sizeof(*us->cr), us->cr, us->cr_dma);
            usb_buffer_free(us->pusb_dev, US_IOBUF_SIZE, us->iobuf,    us->iobuf_dma);
            usb_set_intfdata(us->pusb_intf, NULL);
        scsi_host_put(us_to_host(us));