My blog_title_here

Enabling i2c1 on BeagleBone Black without Device Tree overlays

Important: This way was pretty much made obsolete by Device Tree overlays, which have returned (as expected) in 3.19 kernels - it'd probably be easier to use these in most cases.

BeagleBone Black board has three i2c buses, two of which are available by default on Linux kernel with patches from RCN (Robert Nelson).

Overlays in pre-3.9 allowed to write a "patch" for a Device Tree, compile it and then load it at runtime, which is not possible without these, but perfectly possible and kinda-easy to do by compiling a dtb and loading it on boot.

It'd be great if there was a prebuilt dtb file in Linux with just i2c1 enabled (not just for some cape, bundled with other settings), but unfortunately, as of patched 3.18.4, there doesn't seem to be one, hence the following patching process.

For that, getting the kernel sources (whichever were used to build the kernel, ideally) is necessary.

With kernel sources unpacked, the file that you'd want to patch is "arch/arm/boot/dts/am335x-boneblack.dts" (or whichever other dtb you're loading via uboot):

--- am335x-boneblack.dts.bak    2015-01-29 18:20:29.547909768 +0500
+++ am335x-boneblack.dts        2015-01-30 20:56:43.129213998 +0500
@@ -23,6 +23,14 @@
 };

 &ocp {
+       /* i2c */
+       P9_17_pinmux {
+               status = "disabled";
+       };
+       P9_18_pinmux {
+               status = "disabled";
+       };
+
        /* clkout2 */
        P9_41_pinmux {
                status = "disabled";
@@ -33,6 +41,13 @@
        };
 };

+&i2c1 {
+       status = "okay";
+       pinctrl-names = "default";
+       pinctrl-0 = <&i2c1_pins>;
+       clock-frequency = <100000>;
+};
+
 &mmc1 {
        vmmc-supply = <&vmmcsd_fixed>;
 };

Then "make dtbs" can be used to build dtb files only, and not the whole kernel (which would take a while on BBB).

Resulting *.dtb (e.g. "am335x-boneblack.dtb" for "am335x-boneblack.dts", in the same dir) can be put into "dtbs" on boot partition and loaded from uEnv.txt (or whatever uboot configs are included from there).

Reboot, and i2cdetect -l should show i2c-1:

# i2cdetect -l
i2c-0   i2c             OMAP I2C adapter                    I2C adapter
i2c-1   i2c             OMAP I2C adapter                    I2C adapter
i2c-2   i2c             OMAP I2C adapter                    I2C adapter

As I've already mentioned before, this might not be the optimal way to enable the thing in kernels 3.19 and beyond, if "device tree overlays" patches will land there - it should be possible to just load some patch on-the-fly there, without all the extra hassle described above.

Update 2015-03-19: Device Tree overlays landed in 3.19 indeed, but if migrating to use these is too much hassle for now, here's a patch for 3.19.1-bone4 am335x-bone-common.dtsi to enable i2c1 and i2c2 on boot (applies in the same way, make dtbs, copy am335x-boneblack.dtb to /boot/dtbs).

Sample code for using ST7032I I2C/SMBus driver in Midas LCD with python

I'm using Midas MCCOG21605C6W-SPTLYI 2x16 chars LCD panel, connected to 5V VDD and 3.3V BeagleBone Black I2C bus:

Code for the above LCD clock "app" (python 2.7):

import smbus, time

class ST7032I(object):

  def __init__(self, addr, i2c_chan, **init_kws):
    self.addr, self.bus = addr, smbus.SMBus(i2c_chan)
    self.init(**init_kws)

  def _write(self, data, cmd=0, delay=None):
    self.bus.write_i2c_block_data(self.addr, cmd, list(data))
    if delay: time.sleep(delay)

  def init(self, contrast=0x10, icon=False, booster=False):
    assert contrast < 0x40 # 6 bits only, probably not used on most lcds
    pic_high = 0b0111 << 4 | (contrast & 0x0f) # c3 c2 c1 c0
    pic_low = ( 0b0101 << 4 |
      icon << 3 | booster << 2 | ((contrast >> 4) & 0x03) ) # c5 c4
    self._write([0x38, 0x39, 0x14, pic_high, pic_low, 0x6c], delay=0.01)
    self._write([0x0c, 0x01, 0x06], delay=0.01)

  def move(self, row=0, col=0):
    assert 0 <= row <= 1 and 0 <= col <= 15, [row, col]
    self._write([0b1000 << 4 | (0x40 * row + col)])

  def addstr(self, chars, pos=None):
    if pos is not None:
      row, col = (pos, 0) if isinstance(pos, int) else pos
      self.move(row, col)
    self._write(map(ord, chars), cmd=0x40)

  def clear(self):
    self._write([0x01])

if __name__ == '__main__':
  lcd = ST7032I(0x3e, 2)
  while True:
    ts_tuple = time.localtime()
    lcd.clear()
    lcd.addstr(time.strftime('date: %y-%m-%d', ts_tuple), 0)
    lcd.addstr(time.strftime('time: %H:%M:%S', ts_tuple), 1)
    time.sleep(1)

Even with the same exact display, but connected to 3.3V, these numbers should probably be a bit different - check the datasheet (e.g. page-7 there).

Also note the "addr" and "i2c_chan" values (0x3E and 2) - these should be taken from the board itself.

And the address is easy to get from the datasheet (lcd I have uses only one static slave address), or detect via i2cdetect -r -y <i2c_chan>, e.g.:

# i2cdetect -r -y 2
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- 3e --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Here I have DS1307 RTC on 0x68 and an LCD panel on 0x3E address (again, also specified in the datasheet).

Plugging these bus number and the address for your particular hardware into the script above and maybe adjusting the values there for your lcd panel modes should make the clock show up and tick every second.

In general, upon seeing tutorial on some random blog (like this one), please take it with a grain of salt, because it's highly likely that it was written by a fairly incompetent person (like me), since engineers who deal with these things every day don't see above steps as any kind of accomplishment - it's a boring no-brainer routine for them, and they aren't likely to even think about it, much less write tutorials on it (all trivial and obvious, after all).

Nevertheless, hope this post might be useful to someone as a pointer on where to look to get such device started, if nothing else.

Starting systemd service instance for device from udev

Needed to implement a thing that would react on USB Flash Drive inserted (into autonomous BBB device) - to get device name, mount fs there, rsync stuff to it, unmount.

To avoid whatever concurrency issues (i.e. multiple things screwing with device in parallel), proper error logging and other startup things, most obvious thing is to wrap the script in a systemd oneshot service.

Only non-immediately-obvious problem for me here was how to pass device to such service properly.

With a bit of digging through google results (and even finding one post here somehow among them), eventually found "Pairing udev's SYSTEMD_WANTS and systemd's templated units" resolved thread, where what seem to be current-best approach is specified.

Adapting it for my case and pairing with generic patterns for device-instantiated services, resulted in the following configuration.

99-sync-sensor-logs.rules:

SUBSYSTEM=="block", ACTION=="add", ENV{ID_TYPE}="disk", ENV{DEVTYPE}=="partition",\
  PROGRAM="/usr/bin/systemd-escape -p --template=sync-sensor-logs@.service $env{DEVNAME}",\
  ENV{SYSTEMD_WANTS}+="%c"

sync-sensor-logs@.service:

[Unit]
BindTo=%i.device
After=%i.device

[Service]
Type=oneshot
TimeoutStartSec=300
ExecStart=/usr/local/sbin/sync-sensor-logs /%I

Does not need things like systemctl invocation or manual systemd escaping re-implementation either, though running "systemd-escape" still seem to be necessary evil there.

systemd-less alternative seem to be having a script that does per-device flock, timeout logic and a lot more checks for whether device is ready and/or still there, so this approach looks way saner and clearer, with a caveat that one should probably be familiar with all these systemd features.

A few recent emacs features - remote and file colors

I've been using emacs for a while now, and always on a lookout for a features that'd be nice to have there. Accumulated quite a number of these in my emacs-setup repo as a result.

Recently added two of these, and wanted to share/log the ideas here, in case someone else might find these useful.

% ece b
* 2014-12-23.a_few_recent_emacs_features_-_remote_and_file_colors.rst
  fg_remote.el
  rpc.py
* fg_erc.el
  utils.py
  #twitter_bitlbee
  #blazer
  #exherbo
  ...

% ece b remote
*ERROR*: Failed to uniquely match buffer by `remote', matches:
2014-12-23.a_few_recent_emacs_features_-_remote_and_file_colors.rst,
fg_remote.el

--- whoops... lemme try again

% ece b fg_rem
...(contents of the buffer, matched by unique name part)...

% ece erc
004 #twitter_bitlbee
004 #blazer
002 #bordercamp

--- Showing last (unchecked) irc activity, same as erc-track-mode does (but nicer)

% ece erc twitter | t
[13:36:45]<fijall> hint - you can use gc.garbage in Python to store any sort of ...
[14:57:59]<veorq> Going shopping downtown. Pray for me.
[15:48:59]<mitsuhiko> I like how if you google for "London Bridge" you get ...
[17:15:15]<simonw> TIL the Devonshire word "frawsy" (or is it "frawzy"?) - a ...
[17:17:04] *** -------------------- ***
[17:24:01]<veorq> RT @collinrm: Any opinions on VeraCrypt?
[17:33:31]<veorq> insightful comment by @jmgosney about the Ars Technica hack ...
[17:35:36]<veorq> .@jmgosney as you must know "iterating" a hash is in theory ...
[17:51:50]<veorq> woops #31c3 via @joernchen ...
~erc/#twitter_bitlbee%

--- "t" above is an alias for "tail" that I use in all shells, lines snipped jic

% ece h
Available commands:
  buffer (aliases: b, buff)
  buffer-names
  erc
  erc-mark
  get-socket-type
  help (aliases: h, rtfm, wat)
  log
  switch-sockets

% ece h erc-mark
(fg-remote-erc-mark PATTERN)

Put /mark to a specified ERC chan and reset its activity track.

--- Whole "help" thing is auto-generated, see "fg-remote-help" in fg_remote.el

(defun fg-remote-buffer-save (pattern)
  "Saves specified bufffer, matched via `fg-get-useful-buffer'."
  (with-current-buffer (fg-get-useful-buffer pattern) (save-buffer)))
(defalias 'fg-remote-bs 'fg-remote-buffer-save)

(fg-color-tweak COLOR &optional SEED MIN-SHIFT MAX-SHIFT (CLAMP-RGB-AFTER 20)
  (LAB-RANGES ...))

Adjust COLOR based on (md5 of-) SEED and MIN-SHIFT / MAX-SHIFT lists.

COLOR can be provided as a three-value (0-1 float)
R G B list, or a string suitable for `color-name-to-rgb'.

MIN-SHIFT / MAX-SHIFT can be:
 * three-value list (numbers) of min/max offset on L*a*b* in either direction
 * one number - min/max cie-de2000 distance
 * four-value list of offsets and distance, combining both options above
 * nil for no-limit

SEED can be number, string or nil.
Empty string or nil passed as SEED will return the original color.

CLAMP-RGB-AFTER defines how many attempts to make in picking
L*a*b* color with random offset that translates to non-imaginary sRGB color.
When that number is reached, last color will be `color-clamp'ed to fit into sRGB.

Returns color plus/minus offset as a hex string.
Resulting color offset should be uniformly distributed between min/max shift limits.

Simple aufs setup for Arch Linux ARM and boards like RPi, BBB or Cubie

Experimenting with all kinds of arm boards lately (nyms above stand for Raspberry Pi, Beaglebone Black and Cubieboard), I can't help but feel a bit sorry of microsd cards in each one of them.

These are even worse for non-bulk writes than SSD, having less erase cycles plus larger blocks, and yet when used for all fs needs of the board, even typing "ls" into shell will usually emit a write (unless shell doesn't keep history, which sucks).

Great explaination of how they work can be found on LWN (as usual).

Easy and relatively hassle-free way to fix the issue is to use aufs, but as doing it for the whole rootfs requires initramfs (which is not needed here otherwise), it's a lot easier to only use it for commonly-writable parts - i.e. /var and /home in most cases.

Home for "root" user is usually /root, so to make it aufs material as well, it's better to move that to /home (which probably shouldn't be a separate fs on these devices), leaving /root as a symlink to that.

It seem to be impossible to do when logged-in as /root (mv will error with EBUSY), but trivial from any other machine:

# mount /dev/sdb2 /mnt # mount microsd
# cd /mnt
# mv root home/
# ln -s home/root
# cd
# umount /mnt

As aufs2 is already built into Arch Linux ARM kernel, only thing that's left is to add early-boot systemd unit for mounting it, e.g. /etc/systemd/system/aufs.service:

[Unit]
DefaultDependencies=false

[Install]
WantedBy=local-fs-pre.target

[Service]
Type=oneshot
RemainAfterExit=true

# Remount /home and /var as aufs
ExecStart=/bin/mount -t tmpfs tmpfs /aufs/rw
ExecStart=/bin/mkdir -p -m0755 /aufs/rw/var /aufs/rw/home
ExecStart=/bin/mount -t aufs -o br:/aufs/rw/var=rw:/var=ro none /var
ExecStart=/bin/mount -t aufs -o br:/aufs/rw/home=rw:/home=ro none /home

# Mount "pure" root to /aufs/ro for syncing changes
ExecStart=/bin/mount --bind / /aufs/ro
ExecStart=/bin/mount --make-private /aufs/ro

And then create the dirs used there and enable unit:

# mkdir -p /aufs/{rw,ro}
# systemctl enable aufs

Now, upon rebooting the board, you'll get aufs mounts for /home and /var, making all the writes there go to respective /aufs/rw dirs on tmpfs while allowing to read all the contents from underlying rootfs.

To make sure systemd doesn't waste extra tmpfs space thinking it can sync logs to /var/log/journal, I'd also suggest to do this (before rebooting with aufs mounts):

# rm -rf /var/log/journal
# ln -s /dev/null /var/log/journal

Can also be done via journald.conf with Storage=volatile.

And depending on the app and how "ok" can loss of this data might be, app dir in /var (e.g. /var/lib/pacman) can be either moved + symlinked to /srv or synced before shutdown or after it's done with writing (for manual oneshot apps like pacman).

For moving stuff back to permanent fs, aubrsync from aufs2-util.git can be used like this:

# aubrsync move /var/ /aufs/rw/var/ /aufs/ro/var/

As even pulling that from shell history can be a bit tedious, I've made a simpler ad-hoc wrapper - aufs_sync - that can be used (with mountpoints similar to presented above) like this:

# aufs_sync
Usage: aufs_sync { copy | move | check } [module]
Example (flushes /var): aufs_sync move var

# aufs_sync check
/aufs/rw
/aufs/rw/home
/aufs/rw/home/root
/aufs/rw/home/root/.histfile
/aufs/rw/home/.wh..wh.orph
/aufs/rw/home/.wh..wh.plnk
/aufs/rw/home/.wh..wh.aufs
/aufs/rw/var
/aufs/rw/var/.wh..wh.orph
/aufs/rw/var/.wh..wh.plnk
/aufs/rw/var/.wh..wh.aufs
--- ... just does "find /aufs/rw"

# aufs_sync move
--- does "aubrsync move" for all dirs in /aufs/rw

Just be sure to check if any new apps might write something important there (right after installing these) and do symlinks (to something like /srv) for their dirs, as even having "aufs_sync copy" on shutdown definitely won't prevent data loss for these on e.g. sudden power blackout or any crashes.

tmux rate-limiting magic against terminal spam/flood lock-ups

Update 2015-11-08: No longer necessary (or even supported in 2.1) - tmux' new "backoff" rate-limiting approach works like a charm with defaults \o/

Had the issue of spammy binary locking-up terminal for a long time, but never bothered to do something about it... until now.

Happens with any terminal I've seen - just run something like this in the shell there:

# for n in {1..500000}; do echo "$spam $n"; done

xterm seem to be one of the most resistant *terms to this, e.g. terminology - much less so, which I guess just means that it's more fancy and hence slower to draw millions of output lines.

Anyhow, tmuxrc magic:

set -g c0-change-trigger 150
set -g c0-change-interval 100

"man tmux" says that 250/100 are defaults, but it doesn't seem to be true, as just setting these "defaults" explicitly here fixes the issue, which exists with the default configuration.

Fix just limits rate of tmux output to basically 150 newlines (which is like twice my terminal height anyway) per 100 ms, so xterm won't get overflown with "rendering megs of text" backlog, remaining apparently-unresponsive (to any other output) for a while.

Since I always run tmux as a top-level multiplexer in xterm, totally solved the annoyance for me. Just wish I've done that much sooner - would've saved me a lot of time and probably some rage-burned neurons.

(yet another) Dynamic DNS thing for tinydns (djbdns)

Tried to find any simple script to update tinydns (part of djbdns) zones that'd be better than ssh dns_update@remote_host update.sh, but failed - they all seem to be hacky php scripts, doomed to run behind httpds, send passwords in url, query random "myip" hosts or something like that.

What I want instead is something that won't be making http, tls or ssh connections (and stirring all the crap behind these), but would rather just send udp or even icmp pings to remotes, which should be enough for update, given source IPs of these packets and some authentication payload.

So yep, wrote my own scripts for that - tinydns-dynamic-dns-updater project.

Tool sends UDP packets with 100 bytes of "( key_id || timestamp ) || Ed25519_sig" from clients, authenticating and distinguishing these server-side by their signing keys ("key_id" there is to avoid iterating over them all, checking which matches signature).

Server zone files can have "# dynamic: ts key1 key2 ..." comments before records (separated from static records after these by comments or empty lines), which says that any source IPs of packets with correct signatures (and more recent timestamps) will be recorded in A/AAAA records (depending on source AF) that follow instead of what's already there, leaving anything else in the file intact.

Zone file only gets replaced if something is actually updated and it's possible to use dynamic IP for server as well, using dynamic hostname on client (which is resolved for each delayed packet).

Lossy nature of UDP can be easily mitigated by passing e.g. "-n5" to the client script, so it'd send 5 packets (with exponential delays by default, configurable via --send-delay), plus just having the thing on fairly regular intervals in crontab.

Putting server script into socket-activated systemd service file also makes all daemon-specific pains like using privileged ports (and most other security/access things), startup/daemonization, restarts, auto-suspend timeout and logging woes just go away, so there's --systemd flag for that too.

Given how easy it is to run djbdns/tinydns instance, there really doesn't seem to be any compelling reason not to use your own dynamic dns stuff for every single machine or device that can run simple python scripts.

Github link: tinydns-dynamic-dns-updater

Running isolated Steam instance with its own UID and session

Given that Steam is a closed-source proprietary DRM platform for mass software distribution, it seem to be either an ideal malware spread vector or just a recipie for disaster, so of course not keen on giving it any access in a non-dedicated os.

So, isolation:

• To avoid having Steam and any games anywhere near $HOME, giving it separate UID is a good way to go.

• That should also allow for it to run in a separate desktop session - i.e. have its own cgroup, to easily contain, control and set limits for games:

  % loginctl user-status steam
  steam (1001)
    Since: Sun 2014-06-15 18:40:34 YEKT; 31s ago
    State: active
    Sessions: *7
      Unit: user-1001.slice
            └─session-7.scope
              ├─7821 sshd: steam [priv]
              ├─7829 sshd: steam@notty
              ├─7830 -zsh
              ├─7831 bash /usr/bin/steam
              ├─7841 bash /home/steam/.local/share/Steam/steam.sh
              ├─7842 tee /tmp/dumps/steam_stdout.txt
              ├─7917 /home/steam/.local/share/Steam/ubuntu12_32/steam
              ├─7942 dbus-launch --autolaunch=e52019f6d7b9427697a152348e9f84ad ...
              └─7943 /usr/bin/dbus-daemon --fork --print-pid 5 ...
  

• AppArmor should allow to further isolate processes from having any access beyond what's absolutely necessary for them to run, warn when these try to do strange things and allow to just restrict these from doing outright stupid things.

• Given separate UID and cgroup, network access from all Steam apps can be easily controlled via e.g. iptables, to avoid Steam and games scanning and abusing other things in LAN, for example.

Creating steam user should be as simple as useradd steam, but then switching to that UID from within a running DE should still allow it to access same X server and start systemd session for it, plus not have any extra env, permissions, dbus access, fd's and such from the main session.

To allow access to X, xhost or ~/.Xauthority cookie can be used along with some extra env in e.g. ~/.zshrc:

export DISPLAY=':1.0'

In similar to ssh fashion, I've used pulseaudio network streaming to main DE sound daemon on localhost for sound (also in ~/.zshrc):

export PULSE_SERVER='{e52019f6d7b9427697a152348e9f84ad}tcp6:malediction:4713'
export PULSE_COOKIE="$HOME"/.pulse-cookie

(I have pulse network streaming setup anyway, for sharing sound from desktop to laptop - to e.g. play videos on a big screen there yet hear sound from laptop's headphones)

Running Steam will also start its own dbus session (maybe it's pulse client lib doing that, didn't check), but it doesn't seem to be used for anything, so there seem to be no need to share it with main DE.

That should allow to start Steam after ssh'ing to steam@localhost, but process can be made much easier (and more foolproof) with e.g. ~/bin/steam as:

#!/bin/bash

cmd=$1
shift

steam_wait_exit() {
  for n in {0..10}; do
    pgrep -U steam -x steam >/dev/null || return 0
    sleep 0.1
  done
  return 1
}

case "$cmd" in
  '')
    ssh steam@localhost <<EOF
source .zshrc
exec steam "$@"
EOF
    loginctl user-status steam ;;

  s*) loginctl user-status steam ;;

  k*)
    steam_exited=
    pgrep -U steam -x steam >/dev/null
    [[ $? -ne 0 ]] && steam_exited=t
    [[ -z "$steam_exited" ]] && {
      ssh steam@localhost <<EOF
source .zshrc
exec steam -shutdown
EOF
      steam_wait_exit
      [[ $? -eq 0 ]] && steam_exited=t
    }
    sudo loginctl kill-user steam
    [[ -z "$steam_exited" ]] && {
      steam_wait_exit || sudo loginctl -s KILL kill-user steam
    } ;;

  *) echo >&2 "Usage: $(basename "$0") [ status | kill ]"
esac

Now just steam in the main DE will run the thing in its own $HOME.

For further convenience, there's steam status and steam kill to easily monitor or shutdown running Steam session from the terminal.

Note the complicated shutdown thing - Steam doesn't react to INT or TERM signals cleanly, passing these to the running games instead, and should be terminated via its own cli option (and the rest can then be killed-off too).

With this setup, iptables rules for outgoing connections can use user-slice cgroup match (in 3.14 at least) or -m owner --uid-owner steam matches for socket owner uid.

The only non-WAN things Steam connects to here are DNS servers and aforementioned pulseaudio socket on localhost, the rest can be safely firewalled.

Finally, running KSP there on Exherbo, I quickly discovered that sound libs and plugins - alsa and pulse - in ubuntu "runtime" steam bootstrap setups don't work well - either there's no sound or game fails to load at all.

Easy fix is to copy the runtime it uses (32-bit one for me) and cleanup alien stuff from there for what's already present in the system, i.e.:

% cp -R .steam/bin32/steam-runtime my-runtime
% find my-runtime -type f\
  \( -path '*asound*' -o -path '*alsa*' -o -path '*pulse*' \) -delete

And then add something like this to ~steam/.zshrc:

steam() { STEAM_RUNTIME="$HOME"/my-runtime command steam "$@"; }

That should keep all of the know-working Ubuntu libs that steam bootsrap gets away from the rest of the system (where stuff like Mono just isn't needed, and others will cause trouble) while allowing to remove any of them from the runtime to use same thing in the system.

And yay - Kerbal Space Program seem to work here way faster than on Win7.

Displaying any lm_sensors data (temperature, fan speeds, voltage, etc) in conky

Conky sure has a ton of sensor-related hw-monitoring options, but it still doesn't seem to be enough to represent even just the temperatures from this "sensors" output:

atk0110-acpi-0
Adapter: ACPI interface
Vcore Voltage:      +1.39 V  (min =  +0.80 V, max =  +1.60 V)
+3.3V Voltage:      +3.36 V  (min =  +2.97 V, max =  +3.63 V)
+5V Voltage:        +5.08 V  (min =  +4.50 V, max =  +5.50 V)
+12V Voltage:      +12.21 V  (min = +10.20 V, max = +13.80 V)
CPU Fan Speed:     2008 RPM  (min =  600 RPM, max = 7200 RPM)
Chassis Fan Speed:    0 RPM  (min =  600 RPM, max = 7200 RPM)
Power Fan Speed:      0 RPM  (min =  600 RPM, max = 7200 RPM)
CPU Temperature:    +42.0°C  (high = +60.0°C, crit = +95.0°C)
MB Temperature:     +43.0°C  (high = +45.0°C, crit = +75.0°C)

k10temp-pci-00c3
Adapter: PCI adapter
temp1:        +30.6°C  (high = +70.0°C)
                       (crit = +90.0°C, hyst = +88.0°C)

radeon-pci-0400
Adapter: PCI adapter
temp1:        +51.0°C

Given the summertime, and faulty noisy cooling fans, decided that it'd be nice to be able to have an idea about what kind of temperatures hw operates on under all sorts of routine tasks.

Conky is extensible via lua, which - among other awesome things there are - allows to code caches for expensive operations (and not just repeat them every other second) and parse output of whatever tools efficiently (i.e. without forking five extra binaries plus perl).

Output of "sensors" though not only is kinda expensive to get, but also hardly parseable, likely unstable, and tool doesn't seem to have any "machine data" option.

lm_sensors includes a libsensors, which still doesn't seem possible to call from conky-lua directly (would need some kind of ffi), but easy to write the wrapper around - i.e. this sens.c 50-liner, to dump info in a useful way:

atk0110-0-0__in0_input 1.392000
atk0110-0-0__in0_min 0.800000
atk0110-0-0__in0_max 1.600000
atk0110-0-0__in1_input 3.360000
...
atk0110-0-0__in3_max 13.800000
atk0110-0-0__fan1_input 2002.000000
atk0110-0-0__fan1_min 600.000000
atk0110-0-0__fan1_max 7200.000000
atk0110-0-0__fan2_input 0.000000
...
atk0110-0-0__fan3_max 7200.000000
atk0110-0-0__temp1_input 42.000000
atk0110-0-0__temp1_max 60.000000
atk0110-0-0__temp1_crit 95.000000
atk0110-0-0__temp2_input 43.000000
atk0110-0-0__temp2_max 45.000000
atk0110-0-0__temp2_crit 75.000000
k10temp-0-c3__temp1_input 31.500000
k10temp-0-c3__temp1_max 70.000000
k10temp-0-c3__temp1_crit 90.000000
k10temp-0-c3__temp1_crit_hyst 88.000000
radeon-0-400__temp1_input 51.000000

It's all lm_sensors seem to know about hw in a simple key-value form.

Still not keen on running that on every conky tick, hence the lua cache:

sensors = {
  values=nil,
  cmd="sens",
  ts_read_i=120, ts_read=0,
}

function conky_sens_read(name, precision)
  local ts = os.time()
  if os.difftime(ts, sensors.ts_read) > sensors.ts_read_i then
    local sh = io.popen(sensors.cmd, 'r')
    sensors.values = {}
    for p in string.gmatch(sh:read('*a'), '(%S+ %S+)\n') do
      local n = string.find(p, ' ')
      sensors.values[string.sub(p, 0, n-1)] = string.sub(p, n)
    end
    sh:close()
    sensors.ts_read = ts
  end

  if sensors.values[name] then
    local fmt = string.format('%%.%sf', precision or 0)
    return string.format(fmt, sensors.values[name])
  end
  return ''
end

Which can run the actual "sens" command every 120s, which is perfectly fine with me, since I don't consider conky to be an "early warning" system, and more of an "have an idea of what's the norm here" one.

Config-wise, it'd be just cpu temp: ${lua sens_read atk0110-0-0__temp1_input}C, or a more fancy template version with a flashing warning and hidden for missing sensors:

template3 ${color lightgrey}${if_empty ${lua sens_read \2}}${else}\
${if_match ${lua sens_read \2} > \3}${color red}\1: ${lua sens_read \2}C${blink !!!}\
${else}\1: ${color}${lua sens_read \2}C${endif}${endif}

It can then be used simply as ${template3 cpu atk0110-0-0__temp1_input 60} or ${template3 gpu radeon-0-400__temp1_input 80}, with 60 and 80 being manually-specified thresholds beyond which indicator turns red and has blinking "!!!" to get more attention.

Overall result in my case is something like this:

sens.c (plus Makefile with gcc -Wall -lsensors for it) and my conky config where it's utilized can be all found in de-setup repo on github (or my git mirror, ofc).

The moment of epic fail hilarity with hashes

Just had an epic moment wrt how to fail at kinda-basic math, which seem to be quite representative of how people fail wrt homebrew crypto code (and what everyone and their mom warn against).

So, anyhow, on a d3 vis, I wanted to get a pseudorandom colors for text blobs, but with reasonably same luminosity on HSL scale (Hue - Saturation - Luminosity/Lightness/Level), so that changing opacity on light/dark bg can be seen clearly as a change of L in the resulting color.

There are text items like (literally, in this example) "thing1", "thing2", "thing3" - these should have all distinct and constant colors, ideally.

So how do you pick H and S components in HSL from a text tag? Just use hash, right?

Didn't want much bias wrt which range of colors get picked, so there are these test results - link1, link2 - wrt how these functions work, e.g. performance and distribution of output values over uint32 range.

Picked random "ok" one - Ly hash, with fairly even output distribution, implemented as this:

hashLy_max = 4294967296 # uint32
hashLy = (str, seed=0) ->
  for n in [0..(str.length-1)]
    c = str.charCodeAt(n)
    while c > 0
      seed = ((seed * 1664525) + (c & 0xff) + 1013904223) % hashLy_max
      c >>= 8
  seed

c >>= 8 line and internal loop here because JS has unicode strings, so it's a trivial (non-standard) encoding.

But given any "thing1" string, I need two 0-255 values: H and S, not one 0-(2^32-1). So let's map output to a 0-255 range and just call it twice:

hashLy_chain = (str, count=2, max=255) ->
  [hash, hashes] = [0, []]
  scale = d3.scale.linear()
    .range([0, max]).domain([0, hashLy_max])
  for n in [1..count]
    hash = hashLy(str, hash)
    hashes.push(scale(hash))
  hashes

Getting the values from this func, noticed that they look kinda non-random at all, which is not what I came to expect from hash functions, quite used to dealing crypto hashes, which are really easy to get in any lang but JS.

So, sure, given that I'm playing around with d3 anyway, let's just plot the outputs:

"Wat?... Oh, right, makes sense."

It's meant for hash tables, where seq-in/seq-out is fine, and the results in "chain(3)[0]" and "chain(3)[1]" calls are so close on 0-255 that they map to the same int value.

Plus, of course, the results are anything but "random-looking", even for non-sequential strings of d3.scale.category20() range.

Lession learned - know what you're dealing with, be super-careful rolling your own math from primitives you don't really understand, stop and think about wth you're doing for a second - don't just rely on "intuition" (associated with e.g. "hash" word).

Now I totally get how people start with AES and SHA1 funcs, mix them into their own crypto protocol and somehow get something analogous to ROT13 (or even double-ROT13, for extra hilarity) as a result.