Sent with Proton Mail secure email. ------- Original Message ------- On Wednesday, November 30th, 2022 at 8:05 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Nov 29, 2022 at 09:15:24PM +0000, hinxx wrote: > > > I'm looking to use a sendfile(2) with a Xilinx XDMA kernel driver in order to move data from a PCIe board with Xilinx FPGA to the network card with "zero-copy". > > > > Currently I'm getting EINVAL return status from sendfile(2) when providing opened XDMA device file descriptor as input fd. > > > > The device driver provides a character device that can be mmap'ed. > > > > There seem to be other restrictions. Can anyone provide insight on what would be needed to make this work? > > > Please contact the authors of your kernel driver, they can answer this > best. > That would make sense, sadly they are MIA on their github repo engagement. But in general, if I write a PCIe, DMA capable char device, what is the general guidance on what it takes to support splice/sendfile from a char device driver? Maybe there is an existing one in the kernel I could look at? Is it even something worth pursuing? This line make me think it might not work for char devices https://elixir.bootlin.com/linux/v5.19.17/source/fs/splice.c#L827. Is going for block device the only way that such device driver can work with the sendfile? Thanks! //hinko
