some first impressions

Mitch Bradley wmb at
Thu Aug 16 15:53:13 EDT 2007

> It might be nice if there were a driver to access the GPIO, but I didn't 
> see one in a quick scan of the kernel source.

It turns out that there is a GPIO driver - the source is in 
char/drivers/cs5535_gpio.c - and it is available as a kernel module:

 modprobe cs5535_gpio

However, nobody that I asked knows how to use it (it doesn't appear in 
/dev/ after you modprobe it, and the correspondence between write() 
calls to that driver and specific operations on the GPIO register block 
isn't clear).

And in any case, accessing this behind alsamixer's back is not a good 
idea, because then alsamixer will be confused about the state.

All in all, I think it's better to call alsamixer to do the work, so the 
state remains consistent between applications.

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