Hello Gerd, > The saa7134 has a iommu which wants a page list in physical memory. > That forms a virtual, 4MB sized I/O space. The saa7146 does the same > as far I know.
> For DMA transfer you have some control registers (start offset, line > padding, ...) for each field. The start offset is needed to fill a > buffer with an interlaced image and to place the overlay at a random > location on the screen, thus I expect the saa7146 has this too. This is true, then the both are really quite similar. Btw: is the full specification for the saa7134 freely available? > The start offset can also be used to let the capture buffer start > at non-page-aligned addresses. I just tried that experimentally in my driver (simply increase the start offset) and it works. Hmm, I never really tried that. Thanks for the kick in the ass... ;-) > If page-alignment is really needed I'd prefeare this way. To make it clear: it's not needed and we don't need to care about it. > If you > allocate memory by mapping anonymous memory it will be page aligned. > shared memory is also page-aligned. And applications can figure the > page size with the "getpagesize()" call, so they have a chance to > do the page-alignment thing themself even for memory allocated via > malloc(). True, but most programmers won't think about this if *their* hardware doesn't have the page boundary restriction -- even if it's noted in the docs. In that case, other users with different hardware won't be very happy. But we can forget about this topic. Sorry for the confusion. > Gerd CU Michael. _______________________________________________ Video4linux-list mailing list [EMAIL PROTECTED] https://listman.redhat.com/mailman/listinfo/video4linux-list
