> Richard> Hi, all. I've implemented a simple new system call called
> Richard> phys_addr() which converts a virtual address to a physical
> Richard> address.
>
> Cool. I needed some of this for the USB Stack; I've been using
> something I found at linux/drivers/char/bttv.c, as I wanted to be able
> to directly do PCI read and writes to user space.
That's what get_user() / put_user() are for. Use them if you want to do
I/O from/to userspace without DMA. Don't even think about translating
the addresses into kernel addresses or on certain architectures all hell
will break loose.
If you want to do DMA then you'll need additional facilities which aren't
yet in place in Linus' kernel release.
Ralf
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