Installing Gentoo on a ThinkPad X1carbon

Specific installation notes for Gentoo on the ThinkPad X1.

Link to X1 main page X1 main page (with standard features list)

USB ethernet dongle U2L100P-Y1

This is the dongle that Lenovo ships with the X1. The device is seen by dmesg as AX88772B and by lsusb

       # lsusb
       Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
       Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
       Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
       Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
       Bus 001 Device 035: ID 17ef:6009 Lenovo ThinkPad Keyboard with TrackPoint
       Bus 001 Device 003: ID 147e:2020 Upek TouchChip Fingerprint Coprocessor (WBF advanced mode)
       Bus 001 Device 034: ID 0a5c:21e6 Broadcom Corp. BCM20702 Bluetooth 4.0 [ThinkPad]
       Bus 001 Device 005: ID 04f2:b315 Chicony Electronics Co., Ltd 
       Bus 002 Device 011: ID 17ef:7203 Lenovo

Make menuconfig and enable the following:

           Device Drivers  --->
       [*] Network device support  --->
             USB Network Adapters  --->
       <M> Multi-purpose USB Networking Framework
       <M>   ASIX AX88xxx Based USB 2.0 Ethernet Adapters

Get the driver from http://www.asix.com.tw/download.php?sub=driverdetail&PItemID=105 (need v4.4.1)

Unzip, edit asix.c and add the device id 0x17ef:0x7203 if it's missing

       static const struct usb_device_id    products [] = {
            USB_DEVICE (0x04f1, 0x3008),
            .driver_info = (unsigned long) &ax8817x_info,
        }, {
           // Lenovo 10/100
           USB_DEVICE (0x17ef, 0x7203),
           .driver_info = (unsigned long) &ax88772_info,
       }, {
            // ASIX AX88772B 10/100
            USB_DEVICE (0x0b95, 0x772b),
            .driver_info = (unsigned long) &ax88772_info,

Then

        make && make install
        modprobe asix