GPIO on Arch Linux ARM for Raspberry Pi 3 (aarch64)

While everyone appears to prefer that you don't, performance is a bit better on 64bit ALARM vs. 32bit for what I'm doing. Also, I get that warm, tingly feeling of running upstream kernel without odd Broadcom or RPi Foundation patches.

That said, a lot of the basic stuff for managing GPIO isn't available. I had to poke for a few days to figure out what's going on, so I thought I'd document it, partially to save other people time, and partially so it's all in one place when I get back to it.


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2019/02/10 03:38 · sam

Simpler internal bridge for Xen on Arch using netctl

Just change 'Interface' and 'Dummy' appropriately, and you'll have a nice internal bridge for VMs without having to vswitch things.

Description='internal bridge for xen'
IPCustom=("link add $Dummy type dummy"
          "link set $Dummy up"
          "link set $Dummy master $Interface")
2019/01/10 17:37 · sam

Fix Thunderbird's Dumb Reply-To Behavior

  1. Open up the config editor in Edit>Preferences>Advanced, search for “mail.override_list_reply_to”, set to false.
  2. Try to find a better mail client.
  3. Cry at the state of desktop mail apps in Linux.
2018/10/18 19:12 · sam

Oregon Trail Device Board

I saw on Liliputing that they were selling one of those single game systems that had Oregon Trail instead of Frogger or whatever. I thought it might hold local interest a little longer than arcade games that only few of us remember. And then once done, I could do something terrible to it.

Also, I was wondering if they were doing something interesting in the hardware. Alas…

Click on the image for a full size image.

Those are some biggish COB blobs. I instantly thought NES-on-a-chip1) but they look a bit bigger than the standard dual NoaC and ROM splurts onto the substrate.

I should probe around a bit, because of the LCD panel. It looks like a standard panel, and I could probably fit one of the ILI9341 or so panels from ebay in it with few changes.

Also, if it *is* a NoaC, it might have composite video somewhere on the board. That could be interesting.

2018/03/06 21:15 · sam

LVM2 Fixes for Arch Linux

Alright, so I run Xen on Arch Linux, and I use LVM to manage virtual disks, because snapshots take the pain out of life. There's been a longstanding problem in the hand off from initrd to systemd where not every logical volume is activated at boot, and lvmetad2) will end up running twice with both hanging– in an aggravating but also amusing lock race– when there's a large number of logical volumes.

There was a bug on it, but the bug report suggested that fixes had been implemented and I felt like I was on my own. From there I decided that I wouldn't include root in the LVM, and older systems would just have need intervention on boot. Which is fine– the two affected systems are on my desk or in a datacenter, so inadvertent reboots are rare.

Well, today I decided to patch for Intel-horror, and I really looked at the bug report to fix it once and for all.

It turned out to be absurdly simple.

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2018/01/13 02:54 · sam

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of which I have a few samples to work with
needed for snapshots