Hello,

first of all let me say I am new to the forum and I am not pretty sure if this is the right sections for this question, but I couldn't find a more suitable one.

This may sound a little dumb but here it goes.

I have an FPGA development board with PCIe Gen2 x4 and I am trying to develop both a linux driver and FPGA design to be able to read/write memory located in the board from the PC.

After many tries I think I have it. I have made a simple FPGA design with two PCIe BARs and a driver which detects the device and claims the memory regions and enables de device. As comfirmation of that I can see the mapping in /prop/iomem is correct and also the output of lspci -vvv -d:XXXX says "Driver in use: mydriver".

However, now that I have done all this I am stuck at what I suspect is probably the easier part. How do I actually read/write that memory I have just claimed???

I only know a little bit about drivers and I remember a char driver was accessed with file operations and ioctl such as read/write/lseek etc. However I don't think PCI devices are accessed that way right? I mean they are directly mapped to memory...

Anyway I would like to make an app which I can call with some arguments and have it access those memory regions. Until now I have been using devmem2 but it offers very little flexibility and I really want to make my own because I really want to learn how this is done.

Thanks a lot!

EDIT: i have been investigating and I understand mmap() system call can access that space from userland. However I am not sure if this is the way to go... I would like to do this the "proper" way. By that I mean I wan't to make it optimal, robust and coherent. Should my driver module export functions which read/write to pci? should my user apps then import those functions to perform operations?

I dont think you want to develop a "app".
You need to develop a driver for your board.

when I said app I meant a PC application, obviously not a smartphone so called "app".

The thing is that I want to develop both, the driver and the application, and I am not sure how my application should access memory, if it should do so through the driver, I am not sure how that is done.

Most of these boards have some factory support I'd think. Be sure to see what they have on this. It may already be written.

Thanks for the replies,

I am afraid I still don't know if my driver should export some functions which read/write memory by deferencing pointers directly or what...