On Tue, Oct 20, 2015 at 6:54 PM, Greg KH <greg@kroah.com> wrote:
On Tue, Oct 20, 2015 at 11:58:21AM -0400, Kenneth Adam Miller wrote:
So I'm building a uio kernel driver with buildroot, and I've gotten the driver to compile, installed it and can insmod it in the final buildroot target after booting the image with QEMU.
I'm on linux kernel version 3.14, and I followed the guide here:
https://www.kernel.org/doc/htmldocs/uio-howto/userspace_driver.html
And it describes the location on where the device file that should be opened by userland code as either one of two locations:
/dev/uioX, with X being a number
or /sys/class/uio/uioX
But the each of following returns nothing:
ls /dev/uio* ls /sys/class/uio/
After I compile the uio example that is provided in the linux source at source/ drivers/uio/uio.c and uio_dmem_genirq.c, and insmod them, I do modprobe uio and modprobe uio_dmem_genirq and each of those return nothing. However, I do see that /sys/modules/uio and /sys/modules/uio_dmem_genirq
uio.ko is the uio "core", you need a uio driver in order to actually use it.
uio_dmem_genirq is a uio driver, have you added the needed device tree entries to have it actually create a device for you? Without them, this driver can not find any hardware to bind to, and as such, no device node will ever be created.
I didn't know about that. How do I do that? I'm using buildroot; I guess there's something missing in menuconfig or linux-menuconfig.
I would suggest reading the UIO documentation, it should explain all of this for you already. If not, specific questions are always gladly answered.
The one that I linked? I read that repeatedly. What other documentation is there to read? I also read from Essential Linux Device Drivers, and none of them explained that. There has to be something I'm missing. Thanks a lot!
thanks,
greg k-h