Device to device data transfer woes

Mike Oliphant (oliphant@ling.ed.ac.uk)
Fri, 22 Jan 1999 18:13:18 +0000 (GMT)


I am writing a char driver that needs to access the audio system
directly. This is no problem, except that the file operations of the audio
driver expect data to be in user space.

For example, I have data in kernel space in my driver that I want to send
to the audio device by calling audio_write() directly. This results in a
fault when the audio_write() routine tries to map the data into kernel
space despite the fact that it is already there.

Trying to find a solution is driving me mad! At first, I thought that I
could just transfer the data to user space, and then pass it on (even
though this would be a bit silly, as it would involve moving from kernel
space to user space and back again). However, I can't even manage to do
that, as I don't have any user space memory to put the data in, and I
can't find any way of allocating some within the driver.

Any help would be most welcome.

Thanks,

Mike

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