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------- Original Message ------- On Wednesday, November 30th, 2022 at 8:05 AM, Greg KH gregkh@linuxfoundation.org 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