A sniff dump of a PCIe device talking with Linux host

This is just a raw dump of PCIe communication. I wrote a small sniffer on an FPGA and ran some data in a loop to and from the peripheral. The sniffer’s own data was stored while sniffing, so it doesn’t appear in the stream. The whole thing ran on a Linux machine. I thought that [...]

Getting CTRL, shift and num lock back again

This really is a note to future self. All of the sudden, terminal windows on my Fedora 12 ceased to respect num lock, shift and CTRL modifiers, and I somehow figured out that it may have something to do with the fact that I was having a Vmplayer machine running. It’s noted a lot elsewhere, [...]

Fedora Linux: Getting an Ebay-style USB fax/modem to receive a fax

So I bought a cheapo USB modem/fax on Ebay. I have to admit, that I didn’t really expect it to work with my Fedora 12 Linux machine, but it was actually detected as ACM modem, and /dev/ttyACM0 appeared. lsusb -v reveals it’s identified as ID 0572:1329 Conexant Systems (Rockwell), Inc. Note to self: This is [...]

PCI express maximal payload size: Finding it and its impact on bandwidth

Finding the maximal payload manually The truth is, there is no need to do this manually. lspci does the work for us. But looking into the configuration table once and for all helps demystifying the issue. So here we go. According to the PCIe spec (section 7.8), the max_payload_size the card can take is give [...]

Root over NFS: Diskless boot from network

Introduction Since I wanted to develop a kernel module on Linux for a specific piece of hardware, I thought it would be a nice idea to do that on a computer I wouldn’t mind crashing every now and then. Wanting physical access to the target hardware, a bare motherboard with nothing else but the absolute [...]

Loop mounting a partition from a full disk image

This is documented in a lot of other places, but I’d like to be able to find it quickly, so here it is in my own blog. Suppose I want to mount the partition which is /dev/sda3 in normal life: # fdisk -lu linux.img You must set cylinders. You can do this from the extra [...]

Cleaning up duplicate notes on LMMS

Since certain keystrokes can copy notes on exactly the same position where there are already exactly the same notes, it so turned out, that I had some 6-7 identical notes overlapped in certain time slots. This condition is invisible in the GUI editor unless you try to move notes, just to find that there’s still [...]

Fedora 12: Audio headache notes (ALSA and JACK)

Just a few notes about getting the sound working. Pulseaudio Pulseaudio belongs to the Linux Windowization era, meaning there are plenty of instructions of what-to-do-if but very little info about how the machinery works. Because it never fails, right? Who needs that info? My notes about problems with sound from Firefox are in a different [...]

Clearing brightness, contrast, saturation and hue from a previous mplayer session

Using mplayer, I was annoyed that mplayer remembered my brightness, contrast, hue and saturation settings, which I had tweaked with the keyboard controls the last time I used mplayer. I tried to find where it keeps that info, but didn’t find it anywhere. Then it turned out, that mplayer changes these settings on the X [...]

Linux 2.6.36: When everything freezes

There’s a bug in the kernel, which causes the Big TTY Mutex to be held for some 30 seconds every time certain TTY devices are closed. During these 30 seconds, no TTY operation is possible (including pseudo terminals), which practically means that most, if not all communication with the keyboard is stalled. Since GUI applications [...]