Asking for information about ALSA's kselftest

[Giacomo Guiduzzi]

   Good morning Mr. Broonie and users of the alsa-devel mailing list,


   I’m a student at the University of Modena and Reggio Emilia. I am
   working at the Kernel Hacking course’s exam, a course kept by Paolo
   Valente which introduces students to the world of the Linux kernel and
   its magic. 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 as 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 which 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