Using pci_map_single for multiple dma transfer

Abdul Basit · 08-13-2015, 12:25 AM

I am going through the kernel source documentation at this link http://lwn.net/2001/0712/a/dma-interface.php3. It mentions that pci_map_single can be used for only single transfer. I am writing a PCI driver and device writes to buffer 4KB data at every 500 us . After that it will give an interrupt. I tried to work with pci_alloc_consistent but it is constantly producing error stating "coherent DMA mask is smaller than system GFP_DMA mask arm". My question is how can I use pci_map_single for multiple dma transfers

smallpond · 08-13-2015, 04:34 PM

I think you misread. The single in pci_map_single is referring to a single, contiguous region, not a single transfer. You can use it as many times as you want until you call pci_unmap_single.