Linux移植E20模块驱动步骤解析

以openwrt-hiwooya-stable 源码为例， 对应的内核为 linux-3.18.45。 当然， 如果您是其他
版本的 Linux 系统， 也可参考本章内容进行修改， 大同小异。
（1）添加VIDD和PID

File: [KERNEL]/drivers/usb/serial/option.c

static const struct usb_device_id option_ids[] = {
#if 1 //Added by Quectel
{ USB_DEVICE(0x05C6, 0x9090) }, /* Quectel UC15 */
{ USB_DEVICE(0x05C6, 0x9003) }, /* Quectel UC20 */
{ USB_DEVICE(0x05C6, 0x9215) }, /* Quectel EC20 */
{ USB_DEVICE(0x2C7C, 0x0125) }, /* Quectel EC25 */
{ USB_DEVICE(0x2C7C, 0x0121) }, /* Quectel EC21 */
#endif

[KERNEL]/drivers/usb/serial/qcserial.c

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

[KERNEL]/drivers/net/usb/qmi_wwan.c

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

（2）添加 Zero Packet 机制
在传输大量数据的时候， USB 协议需要添加处理 Zero Packet 的机制。
对于高于 2.6.34 的内核版本， 需要做如下修改。
File: [KERNEL]/drivers/usb/serial/usb_wwan.c

static struct urb *usb_wwan_setup_urb(struct usb_serial *serial, int endpoint,
int dir, void *ctx, char *buf, int len,void (*callback) (struct urb *))
{
……
usb_fill_bulk_urb(urb, serial->dev,
usb_sndbulkpipe(serial->dev, endpoint) | dir,
buf, len, callback, ctx);
#if 1 //Added by Quectel for Zero Packet
if (dir == USB_DIR_OUT) {
struct usb_device_descriptor *desc = &serial->dev->descriptor;
if (desc->idVendor == cpu_to_le16(0x05C6) && desc->idProduct == cpu_to_le16(0x9090))
urb->transfer_flags |= URB_ZERO_PACKET;
if (desc->idVendor == cpu_to_le16(0x05C6) && desc->idProduct == cpu_to_le16(0x9003))
urb->transfer_flags |= URB_ZERO_PACKET;
if (desc->idVendor == cpu_to_le16(0x05C6) && desc->idProduct == cpu_to_le16(0x9215))
urb->transfer_flags |= URB_ZERO_PACKET;
if (desc->idVendor == cpu_to_le16(0x2C7C))
urb->transfer_flags |= URB_ZERO_PACKET;
}
#endif
return urb;
}

（3）添加 Reset Resume
对于一些 USB 控制器， 当主控进入休眠或者待机模式时， 它将掉电或者重启。 而当主控
退出休眠或者待机模式时， USB 主控将不能重启 USB 设备， 反而， 它将执行 Reset Resume，
因此我们需要添加如下内容。
对于高于 3.4 的内核版本， 需要做如下修改。
File: [KERNEL]/drivers/usb/serial/option.c

static struct usb_serial_driver option_1port_device = {
……
#ifdef CONFIG_PM
.suspend = usb_wwan_suspend,
.resume = usb_wwan_resume,
#if 1 //Added by Quectel
.reset_resume = usb_wwan_resume,
#endif
#endif
};

（4）使用 GobiNet 或者 QMI 驱动
对于高于 2.6.30 的内核版本， 需要做如下修改。
File: [KERNEL]/drivers/usb/serial/option.c

static int option_probe(struct usb_serial *serial, const struct usb_device_id *id) {
struct usb_wwan_intf_private *data;
……
#if 1 //Added by Quectel
//Quectel UC20's interface 4 can be used as USB Network device
if (serial->dev->descriptor.idVendor == cpu_to_le16(0x05C6) &&
serial->dev->descriptor.idProduct == cpu_to_le16(0x9003)
&& serial->interface->cur_altsetting->desc.bInterfaceNumber >= 4)
return -ENODEV;
//Quectel EC20's interface 4 can be used as USB Network device
if (serial->dev->descriptor.idVendor == cpu_to_le16(0x05C6) &&
serial->dev->descriptor.idProduct == cpu_to_le16(0x9215)
&& serial->interface->cur_altsetting->desc.bInterfaceNumber >= 4)
return -ENODEV;
//Quectel EC25&EC21's interface 4 can be used as USB Network device
if (serial->dev->descriptor.idVendor == cpu_to_le16(0x2C7C)
&& serial->interface->cur_altsetting->desc.bInterfaceNumber >= 4)
return -ENODEV;
#endif
/* Store device id so we can use it during attach. */
usb_set_serial_data(serial, (void *)id);
return 0;
}

（5）修改内核配置
经过上面对源码的修改以后， 我们还需要进行相关内核的配置， 才能真正的支持 USB 串
口驱动。
总的来说， 我们需要将以下内容， 配置进内核即可。
输入make menuconfig
配置 kmod-usb-serial

Kernel modules --->
USB Support --->
<*> kmod-usb-serial..................... Support for USB-to-Serial converters

配置 kmod-usb-serial-option

Kernel modules --->
USB Support --->
<*> kmod-usb-serial-option................... Support for Option HSDPA modems

配置 kmod-usb-serial-wwan

Kernel modules --->
USB Support --->
-*- kmod-usb-serial-wwan..................... Support for GSM and CDMA modems

配置 kmod-usb-net

Kernel modules --->
USB Support --->
<*> kmod-usb-net............... Kernel modules for USB-to-Ethernet convertors

配置 usb-modeswitch

Utilities --->
<*> usb-modeswitch................................ USB mode switching utility

（6）修改内核配置
输入 make kernel_menuconfig

Device Drivers --->
[*] USB support --->
<*> Support for Host-side USB
Device Drivers --->
[*] Network device support --->
<*> USB Network Adapters --->
<*> Multi-purpose USB Networking Framework