Asking for information about ALSA's kselftest

[Giacomo Guiduzzi]

[RESENDING BECAUSE BOUNCED BY SPAMASSASSIN]


Greetings Mr. Brown and users of the alsa-devel mailing list,

I’m a student at the University of Modena and Reggio Emilia. I am 
working on the Kernel Hacking course’s exam, a course kept by Paolo 
Valente which introduces students to the world of the Linux kernel and 
its magics. I was taking a look at the kernel’s kselftests from Linus 
Torvald’s repository to find some test to fix for the exam and I 
stumbled upon the ALSA’s selftest, which I’ve passed the last few days 
on, debugging and exploring. During the execution the test goes as it 
should except for two or three tests. Until now I’ve tried understanding 
test 71, which sometimes succeeds and sometimes fails, and test 72. I 
have no previous knowledge of how ALSA works and I’m completely new to 
the kselftests and the kernel in general. Test 71 gives the following 
output:


# Surround Playback Volume.0 expected 0 but read 1, is_volatile 0
# Surround Playback Volume.1 expected 1 but read 0, is_volatile 0
not ok 71 write_default.0.22


I wanted to ask you if it is normal or not that this test fails on my 
hardware, and if not, what I could do to debug the problem and give you 
useful information to help understand what the issue is. I am currently 
testing on an Ubuntu Desktop VirtualBox VM on kernel 5.17.0-rc3. The 
audio hardware (as the output of the lshw command, multimedia section) is:


description: Multimedia audio controller
product: 82801AA AC'97 Audio Controller
vendor: Intel Corporation
physical id: 5
bus info: pci at 0000:00:05.0
version: 01
width: 32 bits
clock: 33MHz
capabilities: bus_master
configuration: driver=snd_intel8x0 latency=64
resources: irq:21 ioport:d100(size=256) ioport:d200(size=64)


 From what I have seen until now it doesn’t look like a bug from the 
test nor an issue from the kernel, so I’m not really sure where to look 
at: I have compiled alsalib’s source code from the Git repo with debug 
symbols and I’ve followed the execution of the test until I reached a 
call to the ioctl syscall, which doesn’t return an error code so it 
doesn’t look like the problem relies in the kernel; I’m no expert 
though, I’ll let you confirm this or not.

I am at your complete disposal to give you any further useful 
information as I can’t do much more from my side alone.

Thank you in advance, looking forward to your kind response.


Best Regards,

Giacomo Guiduzzi