configfs do not mount device-tree/overlays

5
votes

I'm working on a Cyclone V SOC FPGA from Altera with a double Cortex-A9 processor. The embedded system (linux 4.15.7) is created with Buildroot-2018.02. U-boot is used to load the system i-e FPGA.rbf file, device tree blob and zImage and everything works fine.

I want now to integrate the RBF file to my linux and program the FPGA from Linux. I found several methods and the one I understand is the most common is to use CONFIGFS with a device-tree overlay.

So I changed my device tree to integrate the overlay, the u-boot boot script to disable FPGA load and also the following options in the linux ".config" file with make linux-xconfig :

+CONFIG_OF_OVERLAY=y
+CONFIG_ALTERA_STAPL=y
+CONFIG_CONFIGFS_FS=y
+CONFIG_SAMPLES=y
+CONFIG_SAMPLE_CONFIGFS=m

These options are the state were I am now after several try.

After a make and a reboot, once the kernel is loaded, I enter the following command in the console :

mkdir /config
mount -t configfs none /config

At this state, I'm expecting to see some device tree files in the /config folder but there wasn't any, only one rdma_cm folder :

# ls /config
rdma_cm

I continued my reading on this topic and found that I must enable the CONFIG_OF_CONFIGFS option in my linux kernel.

PROBLEM: This option is not available in my linux kernel. Also, file drivers/of/configfs.c is no here too. I've searched in vain to find how to enable device tree overlay for my kernel version.

How can I configure my kernel to make device-tree available in configfs ?

1
linux-kernelintel-fpgadevice-tree
I may add some informations to help you help me, but I have no idea of which one is relevant. I'll add what's missing on request to prevent a thousand lines post... – grorel

1 Answers

3
votes

I had the same problem as you. So I had to make a device driver by myself.

This device driver is tentative and I expect Linux mainline to officially support Device Tree Overlay ConfigFS.

The device driver I made is available at the following URL.

If you are using Debian, you can build the Debian Package of the device driver with the following URL.

If you want to try Device Tree Overlay using this device driver, please refer to the following URL.