Audio_ioctl (kdev_t dev, unsigned int cmd, void*arg)

Some of the CDROM-ioctls defined in cdrom.h can be implemented by the routines described above, and hence the function cdrom_ioctl will use those. However, most ioctls deal with audio-control. We have decided to leave these accessed through a single function, repeating the arguments cmd and arg. Note that the latter is of type void*, rather than unsigned longI>int. The routine cdrom_ioctl () does do some useful things, though. It sanitizes the address format type to CDROM_MSF (Minutes, Seconds, Frames) for all audio calls. It also verifies the memory location of arg, and reserves stack-memory for the argument. This makes implementation of the audio_ioctl () much simpler than in the old driver scheme. For an example you may look up the function cm206_audio_ioctl () in cm206.c that should be updated with this documentation.

An unimplemented ioctl should return - EINVAL, but a harmless request (e.g., CDROMSTART) may be ignored by returning 0 (success). Other errors should be according to the standards, whatever they are. (We may decide to sanitize the return value in cdrom_ioctl (), in order to guarantee a uniform interface to the audio-player software.)