Hell Labs

Following the patch to fix the si3054 modem detection in the Clevo m540 laptop I noticed, much to my dismay, that slmodemd refused to work spitting out the infamous error period size 48 not supported by playback (64). This error was also discussed in the ALSA bugtracking system. This problem happens in kernels post-2.6.20, specifically in my 2.6.20 with HDA drivers backported from 2.6.22.

Instead of being a bug in ALSA, it seems to me that slmodem should gracefully handle a new period size returned by snd_pcm_hw_params_set_period_size_near() if it differs from the requested period size. It does not, and stops if the value is not exactly what it wants. Proper study of the problem in slmodem’s side is required, however this quick patch solved the issue for me:

• slmodem-2.9.11-alsa-period-size.patch

In my case, ALSA returns 64 when slmodem requests a period size of 48, and everything seems to work well as long as the returned size is larger than the requested size.

Update: the slmodemd hack works with the m540, but not with the LG LW20. Both use a si3054 codec.

Another update: it seems that it worked with the HP Pavilion DV6567CL.

Here are some patches for ALSA to fix issues with 5.1 surround in some machines (LG LW20 laptop, HP Nettle, HP Lucknow), headphone detection (HP Spartan laptop), modem detection (Clevo m540 laptop, sold under different names such as Positivo V44 in Brazil) and USB MIDI quirk (Roland Juno-G synth). All those were sent to Takashi for inclusion in 2.6.23, but if you’re stuck with an older kernel, can’t upgrade your ALSA and have experienced problems with any of the pieces of hardware listed above, you can try one or more of the following patches:

• Fix 5.1 output in LG LW20
• Add quirk for Roland Juno-G (use if usb-midi doesn’t work)
• Add quirk for HP Spartan (fixes headphone detection)
• Add quirk for HP Nettle
• Fix 5.1 surround in HP Nettle
• Add HP Lucknow 5.1 sound support
• Add quirk for si3054 modem detection in Clevo m540