Dear Mark
Thank you for your advice.
Underrun means that the driver is consuming data more quickly than aplay is able to provide it. This may mean that there's some system performance problem or it may be due to your driver is consuming data more quickly than it should and causing problems further up the stack.
I could understand. I will re-check my code, system and more. Thank you
o sometimes BUG_ON is called when I use kmalloc on
(snip)
You shouldn't be using kmalloc() there, no - the trigger function is called from an atomic context where only very limited memory allocation is possible.
Hmm. OK. Thank you. The driver that I referred have used kmalloc on trigger funtion. Maybe it have same bug =).
I'll have a look at your code, but it's likely to be a few days before I have time to do so.
Thank you very much.
Best regards -- Kuninori Morimoto