usb.c

底层驱动开发

		return -EIO;
	}

	/* Calculate and store the pipe values */
	us->send_ctrl_pipe = usb_sndctrlpipe(us->pusb_dev, 0);
	us->recv_ctrl_pipe = usb_rcvctrlpipe(us->pusb_dev, 0);
	us->send_bulk_pipe = usb_sndbulkpipe(us->pusb_dev,
		ep_out->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
	us->recv_bulk_pipe = usb_rcvbulkpipe(us->pusb_dev, 
		ep_in->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
	if (ep_int) {
		us->recv_intr_pipe = usb_rcvintpipe(us->pusb_dev,
			ep_int->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
		us->ep_bInterval = ep_int->bInterval;
	}
	return 0;
}

/* Initialize all the dynamic resources we need */
static int usb_stor_acquire_resources(struct us_data *us)
{
	int p;

	us->current_urb = usb_alloc_urb(0, GFP_KERNEL);
	if (!us->current_urb) {
		US_DEBUGP("URB allocation failed\n");
		return -ENOMEM;
	}

	/* Lock the device while we carry out the next two operations */
	down(&us->dev_semaphore);

	/* For bulk-only devices, determine the max LUN value */
	if (us->protocol == US_PR_BULK) {
		p = usb_stor_Bulk_max_lun(us);
		if (p < 0) {
			up(&us->dev_semaphore);
			return p;
		}
		us->max_lun = p;
	}

	/* Just before we start our control thread, initialize
	 * the device if it needs initialization */
	if (us->unusual_dev->initFunction)
		us->unusual_dev->initFunction(us);

	up(&us->dev_semaphore);

	/* Start up our control thread */
	p = kernel_thread(usb_stor_control_thread, us, CLONE_VM);
	if (p < 0) {
		printk(KERN_WARNING USB_STORAGE 
		       "Unable to start control thread\n");
		return p;
	}
	us->pid = p;
	atomic_inc(&total_threads);

	/* Wait for the thread to start */
	wait_for_completion(&(us->notify));

	return 0;
}

/* Release all our dynamic resources */
static void usb_stor_release_resources(struct us_data *us)
{
	US_DEBUGP("-- %s\n", __FUNCTION__);

	/* Tell the control thread to exit.  The SCSI host must
	 * already have been removed so it won't try to queue
	 * any more commands.
	 */
	US_DEBUGP("-- sending exit command to thread\n");
	set_bit(US_FLIDX_DISCONNECTING, &us->flags);
	up(&us->sema);

	/* Call the destructor routine, if it exists */
	if (us->extra_destructor) {
		US_DEBUGP("-- calling extra_destructor()\n");
		us->extra_destructor(us->extra);
	}

	/* Free the extra data and the URB */
	kfree(us->extra);
	usb_free_urb(us->current_urb);
}

/* Dissociate from the USB device */
static void dissociate_dev(struct us_data *us)
{
	US_DEBUGP("-- %s\n", __FUNCTION__);

	/* Free the device-related DMA-mapped buffers */
	if (us->cr)
		usb_buffer_free(us->pusb_dev, sizeof(*us->cr), us->cr,
				us->cr_dma);
	if (us->iobuf)
		usb_buffer_free(us->pusb_dev, US_IOBUF_SIZE, us->iobuf,
				us->iobuf_dma);

	/* Remove our private data from the interface */
	usb_set_intfdata(us->pusb_intf, NULL);
}

/* First stage of disconnect processing: stop all commands and remove
 * the host */
static void quiesce_and_remove_host(struct us_data *us)
{
	/* Prevent new USB transfers, stop the current command, and
	 * interrupt a SCSI-scan or device-reset delay */
	set_bit(US_FLIDX_DISCONNECTING, &us->flags);
	usb_stor_stop_transport(us);
	wake_up(&us->delay_wait);

	/* It doesn't matter if the SCSI-scanning thread is still running.
	 * The thread will exit when it sees the DISCONNECTING flag. */

	/* Wait for the current command to finish, then remove the host */
	down(&us->dev_semaphore);
	up(&us->dev_semaphore);

	/* queuecommand won't accept any new commands and the control
	 * thread won't execute a previously-queued command.  If there
	 * is such a command pending, complete it with an error. */
	if (us->srb) {
		us->srb->result = DID_NO_CONNECT << 16;
		scsi_lock(us_to_host(us));
		us->srb->scsi_done(us->srb);
		us->srb = NULL;
		scsi_unlock(us_to_host(us));
	}

	/* Now we own no commands so it's safe to remove the SCSI host */
	scsi_remove_host(us_to_host(us));
}

/* Second stage of disconnect processing: deallocate all resources */
static void release_everything(struct us_data *us)
{
	usb_stor_release_resources(us);
	dissociate_dev(us);

	/* Drop our reference to the host; the SCSI core will free it
	 * (and "us" along with it) when the refcount becomes 0. */
	scsi_host_put(us_to_host(us));
}

/* Thread to carry out delayed SCSI-device scanning */
static int usb_stor_scan_thread(void * __us)
{
	struct us_data *us = (struct us_data *)__us;

	/*
	 * This thread doesn't need any user-level access,
	 * so get rid of all our resources.
	 */
	lock_kernel();
	daemonize("usb-stor-scan");
	unlock_kernel();

	/* Acquire a reference to the host, so it won't be deallocated
	 * until we're ready to exit */
	scsi_host_get(us_to_host(us));

	/* Signal that we've started the thread */
	complete(&(us->notify));

	printk(KERN_DEBUG
		"usb-storage: device found at %d\n", us->pusb_dev->devnum);

	/* Wait for the timeout to expire or for a disconnect */
	if (delay_use > 0) {
		printk(KERN_DEBUG "usb-storage: waiting for device "
				"to settle before scanning\n");
retry:
		wait_event_interruptible_timeout(us->delay_wait,
				test_bit(US_FLIDX_DISCONNECTING, &us->flags),
				delay_use * HZ);
		if (try_to_freeze())
			goto retry;
	}

	/* If the device is still connected, perform the scanning */
	if (!test_bit(US_FLIDX_DISCONNECTING, &us->flags)) {
		scsi_scan_host(us_to_host(us));
		printk(KERN_DEBUG "usb-storage: device scan complete\n");

		/* Should we unbind if no devices were detected? */
	}

	scsi_host_put(us_to_host(us));
	complete_and_exit(&threads_gone, 0);
}


/* Probe to see if we can drive a newly-connected USB device */
static int storage_probe(struct usb_interface *intf,
			 const struct usb_device_id *id)
{
	struct Scsi_Host *host;
	struct us_data *us;
	const int id_index = id - storage_usb_ids; 
	int result;

	US_DEBUGP("USB Mass Storage device detected\n");

	/*
	 * Ask the SCSI layer to allocate a host structure, with extra
	 * space at the end for our private us_data structure.
	 */
	host = scsi_host_alloc(&usb_stor_host_template, sizeof(*us));
	if (!host) {
		printk(KERN_WARNING USB_STORAGE
			"Unable to allocate the scsi host\n");
		return -ENOMEM;
	}

	us = host_to_us(host);
	memset(us, 0, sizeof(struct us_data));
	init_MUTEX(&(us->dev_semaphore));
	init_MUTEX_LOCKED(&(us->sema));
	init_completion(&(us->notify));
	init_waitqueue_head(&us->delay_wait);

	/* Associate the us_data structure with the USB device */
	result = associate_dev(us, intf);
	if (result)
		goto BadDevice;

	/*
	 * Get the unusual_devs entries and the descriptors
	 *
	 * id_index is calculated in the declaration to be the index number
	 * of the match from the usb_device_id table, so we can find the
	 * corresponding entry in the private table.
	 */
	get_device_info(us, id_index);

#ifdef CONFIG_USB_STORAGE_SDDR09
	if (us->protocol == US_PR_EUSB_SDDR09 ||
			us->protocol == US_PR_DPCM_USB) {
		/* set the configuration -- STALL is an acceptable response here */
		if (us->pusb_dev->actconfig->desc.bConfigurationValue != 1) {
			US_DEBUGP("active config #%d != 1 ??\n", us->pusb_dev
				->actconfig->desc.bConfigurationValue);
			goto BadDevice;
		}
		result = usb_reset_configuration(us->pusb_dev);

		US_DEBUGP("Result of usb_reset_configuration is %d\n", result);
		if (result == -EPIPE) {
			US_DEBUGP("-- stall on control interface\n");
		} else if (result != 0) {
			/* it's not a stall, but another error -- time to bail */
			US_DEBUGP("-- Unknown error.  Rejecting device\n");
			goto BadDevice;
		}
	}
#endif

	/* Get the transport, protocol, and pipe settings */
	result = get_transport(us);
	if (result)
		goto BadDevice;
	result = get_protocol(us);
	if (result)
		goto BadDevice;
	result = get_pipes(us);
	if (result)
		goto BadDevice;

	/* Acquire all the other resources and add the host */
	result = usb_stor_acquire_resources(us);
	if (result)
		goto BadDevice;
	result = scsi_add_host(host, &intf->dev);
	if (result) {
		printk(KERN_WARNING USB_STORAGE
			"Unable to add the scsi host\n");
		goto BadDevice;
	}

	/* Start up the thread for delayed SCSI-device scanning */
	result = kernel_thread(usb_stor_scan_thread, us, CLONE_VM);
	if (result < 0) {
		printk(KERN_WARNING USB_STORAGE 
		       "Unable to start the device-scanning thread\n");
		quiesce_and_remove_host(us);
		goto BadDevice;
	}
	atomic_inc(&total_threads);

	/* Wait for the thread to start */
	wait_for_completion(&(us->notify));

	return 0;

	/* We come here if there are any problems */
BadDevice:
	US_DEBUGP("storage_probe() failed\n");
	release_everything(us);
	return result;
}

/* Handle a disconnect event from the USB core */
static void storage_disconnect(struct usb_interface *intf)
{
	struct us_data *us = usb_get_intfdata(intf);

	US_DEBUGP("storage_disconnect() called\n");
	quiesce_and_remove_host(us);
	release_everything(us);
}

/***********************************************************************
 * Initialization and registration
 ***********************************************************************/

static int __init usb_stor_init(void)
{
	int retval;
	printk(KERN_INFO "Initializing USB Mass Storage driver...\n");

	/* register the driver, return usb_register return code if error */
	retval = usb_register(&usb_storage_driver);
	if (retval == 0)
		printk(KERN_INFO "USB Mass Storage support registered.\n");

	return retval;
}

static void __exit usb_stor_exit(void)
{
	US_DEBUGP("usb_stor_exit() called\n");

	/* Deregister the driver
	 * This will cause disconnect() to be called for each
	 * attached unit
	 */
	US_DEBUGP("-- calling usb_deregister()\n");
	usb_deregister(&usb_storage_driver) ;

	/* Don't return until all of our control and scanning threads
	 * have exited.  Since each thread signals threads_gone as its
	 * last act, we have to call wait_for_completion the right number
	 * of times.
	 */
	while (atomic_read(&total_threads) > 0) {
		wait_for_completion(&threads_gone);
		atomic_dec(&total_threads);
	}
}

module_init(usb_stor_init);
module_exit(usb_stor_exit);