官方提供的镜像已经可以运行了，小弟就想自己编一下系统。首先，尝试了github中bsp的编译，sudo ./build.sh后，得到的东西和教程(minimal system BPI-M2.pdf)中的不一样。
实际是在output/BPI_M2_720P/pack中找到了uboot相关的文件。但是，boot.fex为链接，始终找不到。rootfs还是使用教程中所言的debian。烧写完毕，uboot可以启动，手动输入boot，kernel在启动。到了usb就很慢了，目前没有让它跑完，总觉得好像不太对。最后打印的信息如下：
73.550284] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input5
73.562544] generic-usb 0003:046D:C05A.0004: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
126.912452] usb 1-1.1: USB disconnect, device number 5
128.452576] usb 1-1.1: new low-speed USB device number 6 using sw-ehci
128.590305] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input6
128.602576] generic-usb 0003:046D:C05A.0005: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
181.952452] usb 1-1.1: USB disconnect, device number 6
183.492577] usb 1-1.1: new low-speed USB device number 7 using sw-ehci
183.630288] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input7
183.642554] generic-usb 0003:046D:C05A.0006: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
236.992452] usb 1-1.1: USB disconnect, device number 7
238.532577] usb 1-1.1: new low-speed USB device number 8 using sw-ehci
238.670294] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input8
238.682562] generic-usb 0003:046D:C05A.0007: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
292.032451] usb 1-1.1: USB disconnect, device number 8
293.572577] usb 1-1.1: new low-speed USB device number 9 using sw-ehci
293.710323] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input9
293.722645] generic-usb 0003:046D:C05A.0008: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
347.072479] usb 1-1.1: USB disconnect, device number 9
348.612577] usb 1-1.1: new low-speed USB device number 10 using sw-ehci
348.750287] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input10
348.762649] generic-usb 0003:046D:C05A.0009: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
402.112452] usb 1-1.1: USB disconnect, device number 10
403.652577] usb 1-1.1: new low-speed USB device number 11 using sw-ehci
403.790440] input: Logitech USB Optical Mouse as /devices/platform/sw-ehci.1/usb1/1-1/1-1.1/1-1.1:1.0/input/input11
403.802841] generic-usb 0003:046D:C05A.000A: input,hidraw0: USB HID v1.11 Mouse [Logitech USB Optical Mouse] on usb-sw-ehci-1.1/input0
457.152477] usb 1-1.1: USB disconnect, device number 11
此外，采用github中提供的4.0内核后，完全不知道下载哪些东西到SD卡了。github中只说明了如何编译。跪求指教？非常感谢