[PATCH] kernel/dma: Fix panic caused by passing swiotlb to command line

From: He Zhe setup_io_tlb_npages does not check input argument before passing it to isdigit. The argument would be a NULL pointer if "swiotlb", without its value, is set in command line and thus causes the following panic. PANIC: early exception 0xe3 IP 10:bb9b8e9f error 0 cr2 0x0 [

[PATCH] kernel/dma: Fix panic caused by passing swiotlb to command line

From: He Zhe setup_io_tlb_npages does not check input argument before passing it to isdigit. The argument would be a NULL pointer if "swiotlb", without its value, is set in command line and thus causes the following panic. PANIC: early exception 0xe3 IP 10:bb9b8e9f error 0 cr2 0x0 [