Hi list
I'm a newbie to kernel development, so thanks for being patient.
I'm playing around with the new UIO framework. Basically I try to get access
to some registers on a custom ISA card from userspace. While it works
reading to and writing from the registers with ioread()/iowrite() from
the kernel, I can't seem to get it to work from userspace.
Here's what I've got so far:
request_region(0x400, 0x40, "mydev");
base = ioport_map(0x400, 0x40);
Now I'm able to read/write from kernel:
printk("FPGA version %i\n", ioread8(base + 0x3E));
Now the UIO stuff:
uio_info.mem[0].memtype = UIO_MEM_PHYS;
uio_info.mem[0].addr = (unsigned long) base;
uio_info.mem[0].size = 0x40;
uio_register_device(dev, &uio_info);
That gives me the UIO device:
$ lsuio
uio0: name=uio_mydev, version=0.0.1, events=0
map[0]: addr=0x00010400, size=64
>From userspace I do:
uio_fd = open(/dev/uio0, O_RDWR);
access_address = mmap(NULL, 0x10400, PROT_READ|PROT_WRITE,
MAP_SHARED, uio_fd, 0);
If I understood correctly, I should now be able to read/write directly to
memory locations:
printf("FPGA version: 0x%.2X\n", access_address[0x3E]);
Unfortunately it doesn't seem to work. Could someone point out any
obvious mistakes I might have made?
Thanks for your time,
Christoph
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