Posted Nov 14, 2009 21:01 UTC (Sat) by vleo (guest, #32027)
Parent article: Video buffer pools
I've used hack with top memory allocation since kernel 2.0 times for LML33 original driver (not V4L compatible one). That certainly was source of complications in the hardware/driver install process for the end users.
Zoran 36060/67 JPEG codec chipset supports scatter/gather for coded JPEG data transfers, but interestingly enough - not for raw video transfers, that must go to biggish memory buffer.
Patches for this kind of support have been around for over 10 years, but still that is not seen in the kernel.org kernels.
Is that good or bad? From the perfectionist POV it is good. I will not ever design hardware that does not support S/G... well, not in the final release :-) it's easier to implement just a big buffer, w/o need to bother with s/g, especially in the initial VHDL coding phase.
So, maybe these big buffers should be supported after all in the kernel at large, not only under V4L I hope.