[linux-dvb] Re: Alternative v4 demux API

[Holger Waechtler <holger@convergence.de>]

Michael Hunold wrote:
> In theory, you can write to user space memory from device drivers 
> easily. In practise, most hardware has some sort of DMA limitations (for 
> example 16k aligned memory), so this is not an option unfortunately, 
> because you cannot control memory allocation for userspace.
even if we don't need it her, you can: man (3) memalign. Just for the 
case anybody will need it - maybe for SIMD stuff. Since memalign is 
pretty new and not implemented on all Posix-Systems out there you can 
also use the more portable approach the Mesa people took: align 
(alignment-1) bytes more than you need and then mask out the 
log2(alignment) least significant bits.

Holger



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