Messages in this thread |  | | Subject | Re: Is sendfile all that sexy? | Date | Fri, 19 Jan 2001 18:23:06 +0100 (MET) | From | (Rogier Wolff) |
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Linus Torvalds wrote: > > I wrote a driver for a zoran-chipset frame-grabber card. The "natural" > > way to save a video stream was exactly the way it came out of the > > card. And the card was structured that you could put on an "mpeg > > decoder" (or encoder) chip, and you could DMA the stream directly into > > that chip. > > Ehh.. > > And how many of these chips are out on the market? > > Would you agree that it is less than 0.01% of all PC hardware? Like MUCH > less?
Someone asked me to write a driver for one of these cards. I was assuming that most of them work like this. And I'm never wrong, you know...
> > The way soundcards are commonly programmed, they don't play from their > > own memory, but from main memory. However, they all can play from > > their own memory. > > And how do you synchronize the streams etc? It's a nasty piece of > business, and direct PCI-PCI streaming is not the answer. > > > > And you wouldn't need a new memory zone - the kernel wouldn't ever touch > > > the memory anyway, you'd just ioremap() it if you needed to access it > > > programmatically in addition to the streaming of data off disk. > > > > That's the way things currently work. If you start thinking about it > > as a NUMA, it may improve the situation for "common users" too. > > > > A PC is a NUMA machine! We have disk (swap) and main memory. We also > > have a frame buffer, which doesn't currently fit into our memory > > architecture. > > Don't be silly. It fints _fine_ in our memory architecture. We map it to > xfree86, and we're done with it. > > Using the frame buffer for "backing store" for normal memory is not worth > it. That's what disks are for. Frame buffers are _way_ too small to be > interesting as a memory resource.
It's a silly small resource that suddenly becomes usable should the right infrastructure be in place. It isn't. You're not planning on doing it soonish. Neither am I.
Roger.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* * There are old pilots, and there are bold pilots. * There are also old, bald pilots. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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