The helper2416 development board driver failed to create a device node

muxb

The helper2416 development board driver failed to create a device node [Copy link]

I would like to ask the moderator, for the helper2416 development board, the driver fails to create a device node by calling class_create. Is it because the root file system does not support the udev file system? Thank you. After loading the driver, I create the device node myself and the driver can work normally. I use the 2.6 kernel (HELPER2416-KERNEL2.6.21-V100.tar) recompiled by myself and the root-qtopia.img image provided by jyx.

spacexplorer

We use mdev, which will also automatically create nodes. Sorry for the late reply, I haven't been to the forum often recently...

muxb

Thanks for the reply, I continued debugging and found that class_create returned successfully, but device_create(first_drv_class, NULL, MKDEV(first_drv_major, 0), NULL, "xxx"); This sentence is wrong. It said that the kernel pointer pointed to a null pointer. Specifically: Unable to handle kernel paging request at virtual address 335e3220 Backtrace: [] (vsnprintf+0x0/0x544) from [] (device_create+0x78/0xb4) I recompiled the kernel, burned the kernel and rootfiles, but it's still the same. Please help me, thank you.

muxb

muxb posted on 2019-4-28 18:40 Thank you for your reply, I continued debugging and found that class_create returned successfully, but device_create(first_drv_class, NULL, MKDEV ...

Sorry, I found the reason. You need to use this interface to create a device: class_device_create(first_drv_class, NULL, MKDEV(first_drv_major, 0), NULL, "xxx"); Since the new interface can be compiled but cannot be used, I am a little confused...