在linux3.0.35使用ec20不会生成/dev/ttyUSB节点,本方法可以在linux3.0.35生成/dev/ttyUSB节点，生成/dev/ttyUSB0,/dev/ttyUSB1,/dev/ttyUSB2,/dev/ttyUSB3,其中/dev/ttyUSB2可以使用AT指令和ec20通信

1、vim drivers/usb/serial/option.c

添加下面内容到下图红框位置

/* EC20 */

#define EC20_VENDOR_ID                         0x2c7c

#define EC20_PRODUCT_ID                        0x0125

2、

/* ec20 */

{ USB_DEVICE(EC20_VENDOR_ID,EC20_PRODUCT_ID) },

3、

#if 1 //Added by Quectel

        //Quectel modulesm~@~Ys inte**ce 4 can be used as USBnetwork device

        if (serial->dev->descriptor.idVendor == cpu_to_le16(0x2C7C)) {

                //some inte**ces can be used as USB Network device (ecm, rndis, mbim)

                if (serial->inte**ce->cur_altsetting->desc.bInte**ceClass != 0xFF) {

                        return -ENODEV;

                }

                //inte**ce 4 can be used as USB Network device (qmi)

                else if (serial->inte**ce->cur_altsetting->desc.bInte**ceNumber >=4) {

                        return -ENODEV;

                }

        }

#endif

4、vi drivers/usb/serial/qcserial.c

删除P74

{USB_DEVICE(0x05c6, 0x9215)},   /* Acer Gobi 2000 Modem device (VP413) */