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Feb 04, 2013

E135 backlight

Disclaimer: this article is rather old, and does not reflect linux' current state of brightness on the Thinkpad E135

first, it was fixed on maximum. no tool could change it, /sys/class/backlight/acpi_video0/brightness could be written to and changed, but the backlight didn't. Tried the solutions in1, excluding those which would just echo to above /sys/... file, until I found out Kernel parameter acpi_backlight=vendor did the trick.

Now /sys/class/backlight no longer contained an acpi_video0 directory, but a thinkpad_screen directory, that has the same brightness files, which change on using the Fn keys for brightness change.

If I write to them their content changes, but not the backlight, but at least the Fn key combos work.

Feb 04, 2013

KMix with multiple identically named master channels

On the Thinkpad Edge E135, ALSA recognizes 2 sound cards (0 and 1), of which #1 is the analog one I want to use and control - but not the default one. alsamixer can control it via selecting the entries in its F6 menu, but still it's not the default one. Creating this1 asound.conf fixes that.

Now KMix shows 2 open tabs (both with the label "HD Audio Generic"), one for each card. Unfortunately it defaults to control the digital output with its control-panel icon, too, and worse, the dialog to change that "Master Channel" gets confused by the identical names and just doesn't display any channel, so you can't change it. Fix: Stop KMix (dunno if that's really neccessary, but probably is), open ~/.kde4/share/config/kmixrc and set the MasterMixer= and MasterMixerDevice= entries in the [Global] section. MasterMixer specifies an equivalent to the ALSA card, but apparently 1-indexed (so here it was "ALSA::HD-Audio_Generic:1" and I set it to "ALSA::HD-Audio_Generic:2"), MasterMixerDevice tells the channel which should be controlled as Master ("IEC958:0" here, changed to "Master:0"). Simply look at the end of the section names and compare with the channels displayed in KMix beyond each tab (i.e. card), if you're unsure what entries to set.

Note: In later versions of KMix (IIRC around 4.15) this stopped to work, so I stayed on that version


  1. /etc/asound.conf:

    defaults.pcm.card 1
    defaults.pcm.device 0
    defaults.ctl.card 1