Re: [alsa-devel] about ioctl calls

Lorenzo Fundaró wrote:

I have a program that constantly make ioctl calls like this:

ioctl(4, 0x4122, 0x8b703) ioctl(4, 0x4122, 0xbfb65768)

I suspect that this call pertains to ALSA, since I have straced other programs that play music and they always use in the ioctl request field the 0x4122 code.

This is SNDRV_PCM_IOCTL_HWSYNC.

I am interested on finding out what's in the third argument of the ioctl call, is it a sort of struct that contains the audio samples ?

The samples and some control structures are in mmap()ed memory. This ioctl tells the kernel to synchronize and update hardware status.

There is no third parameter; the values shown are random stack contents.

Regards, Clemens