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Opi Zero missing MIDI module in mainline kernel (snd-seq)


brkl

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Hi! Upgrading to the mainline kernel removes /dev/snd/seq, which is needed for MIDI applications. Synthesizers are my main interest in using these boards, so that is a big loss. Since the module is enabled in the legacy kernel, perhaps this is unintentional and could be added to the mainline kernel? Thank you for all your work.

 

Regards,

 

brkl

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brkl is correct.

 

Configuration of the Kernel for sunxi-next defaults to Sequencer Support being disabled (At least for Orange Pi Zero).  It should be enabled as a Module.

it is in:

 > Device Drivers > Sound card support > Advanced Linux Sound Architecture

 

The Help for the kernel option goes on to say:

Quote

CONFIG_SND_SEQUENCER:                                                                                                                                                                           
 Say Y or M to enable MIDI sequencer and router support.  This                                                                                                
 feature allows routing and enqueueing of MIDI events.  Events                                                                                                
 can be processed at a given time.                                                                                                                                             
                                                                                                                                                                                                 
 Many programs require this feature, so you should enable it                                                                                                                                     
 unless you know what you're doing.

Which means that it should be enabled, or set as a module by default, and not disabled by default.

 

I don't know if the Allwinner support is there for HR Timers.  But if they do support them, then the options:

"HR-timer backend support"

"Use HR-timer as default sequencer timer"

should also be set as Modules.

 

Under Generic Sound Devices,

"Virtual MIDI soundcard" should also be set as a module.

 

Interestingly, under USB Sound Devices, "USB Audio/MIDI Driver" is set as a module, as is "Behringer BCD2000 MIDI driver" and others.  These will be useless without Sequencer support.

 

BRKL:  If you want to help yourself, you should look at the instruction for building Armbian.  Follow them through, its not too difficult, and you can build your own image and kernel with these options enabled, until such time as they become standard.  (And maybe there is some valid reason why they have been disabled in the general case, in which case this may be your only recourse).

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Thank you very much for the reply. If this was the only problem I had, I would follow your advice and compile the kernel. Unfortunately, I have a completely separate problem with the audio programming language Chuck (it's in the repository) which just won't run without stuttering on Orange Pi Zero. I don't know what to do about that, so I'm going to focus on other projects for the time being.

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brkl stuttering in any program sounds like a performance issue.  OPI-Zeros overheat without heatsinks, and then thermal throttle (slow down).  Its possible your OPI Zero is doing that, try running armbianmonitor on a seperate ssh connection while running Chuck.  it will tell you if your orange pi zero is overheating and therefore being slowed down.

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I would still be checking temperature.  Just in case.  The maximum CPU frequency that the kernel will use will drop if temperature goes too high.  So you may not be seeing the whole story just by looking at cpu frequency and Top.

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cpufreq-info should tell the current frequency, shouldn't it? The software will run on pretty weak processors OK, so I really don't think the problem lies with the overheating, although that's something that ought to be dealt with if I actually got the thing working.

 

I appreciate I've derailed this thread from the MIDI observation. I believe it would benefit the kernel a lot to have MIDI enabled.

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On 3. 3. 2018 at 11:44 AM, brkl said:

cpufreq-info should tell the current frequency, shouldn't it?


Yes, if you have a driver for DVFS ... this is not existing yet or not working properly yet in a mainline kernel for A64/H5 boards. This is not as simple as enabling MIDI.

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Philipp Rossak is working on A83T H3 H5 A80 A64 Thermal driver (WIP: Philipp Rossak (embed-3d) wipbranch: sunxi-ths patch v2: contains only a83t and h3) 

 

https://lkml.org/lkml/2018/1/28/406

 

https://github.com/embed-3d/linux/tree/embed-3d/sunxi-ths

 

So once the thermal drive is done, the next step is to implement DVFS operating points and more importantly, cooling devices based on those for safe operation of the SoCs...

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