Linux Firmware Debug Kit (lfdk) provides read/write functions to PCI, IO and memory spaces.
lfdk's deb package is available but it is outdated. I usually download  and compile source code, and run ldfk manually in a terminal (ctrl
- sudo apt-get install -f git libncurses-dev
- git clone https://github.com/alexhungce/lfdk1.git
- cd lfdk
- cd bin
- sudo insmod ./lfdd_drv.ko
- sudo ./lfdk
A familiar screen will pop up
The navigation is to use arrow keys and hotkeys L, M and I to different spaces as instructed on the bottom of the lfdk.
 Built-in lspci command can be used to read PCI configuration space, too
 This is tested in Ubuntu Linux 12.04 to 15.04.
 One can also download the source code from sourceforge.net above.