Do DMA for userland buffer in kernel space

[luo]

I prepare to lock the userland buffer in kernel space and map its address into kernel virtual address. When I get the kernel virtual address, I can call DMA APIs to finish the remaining work. Can my idea work? Are there such kernel APIs, which can lock and map userland buffer in kernel space?

Thanks!

 

[luo]

I use "ioctl syscall" to pass userland buffer into kernel driver.