Messages in this thread | | | Date | Thu, 5 Jul 2001 13:19:20 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | RE: DMA memory limitation? |
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On Thu, 5 Jul 2001, Christophe Beaumont wrote:
> > > > On Thu, 5 Jul 2001, Vasu Varma P V wrote: > > > > > Hi, > > > > > > Is there any limitation on DMA memory we can allocate using > > > kmalloc(size, GFP_DMA)? I am not able to acquire more than > > > 14MB of the mem using this on my PCI SMP box with 256MB ram. > > > I think there is restriction on ISA boards of 16MB. > > > Can we increase it ? > > > > > > thx, > > > Vasu > > > > 14MB of DMA(able) memory? Err. I think you are trying to > > do something you would never need to do. > > > And what is that supposed to be???? >
Did you READ the rest of the carefully-worded paragraphs, carefully, explaining that it ** ISN'T DMA ** memory that you need?
> I have a piece of pretty well designed hardware here... and my > application requires me to have the PCI board to random access > in master mode a whole lot of memory (anywhere from 128MEGS to ^^^^^^^^^^^ You JUST give it the address of any RAM you want to read/write... as explained before. As explained, in a documentation file I specified, you convert the virtual address using a macro that the kernel headers provide.
You can even give it user-mode buffers as long as they are non-paged during the access.
> 1GIG... and possibly more...) so I really do need BIG DMA buffers > (I don't say huge anymore as one can get 1/2 Gig of RAM for just > over 120 bucks???)... > > There is no way I can have the piece of hardware behave in > another fashion... and NO it is NOT broken (when you do BOTH > hardware & software, you know about BOTH limitations... there > are just some cases where you have to face some unique issues). > the mem=1024M works pretty fine once you have figured out how > to handle in a fairly simple way this "reserved" memory... >
This is wrong! Good luck sucker.
> So please software people... ^^^^^^^
I am a Software Engineer, with a long history of hardware design.
Cheers, Dick Johnson
Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
I was going to compile a list of innovations that could be attributed to Microsoft. Once I realized that Ctrl-Alt-Del was handled in the BIOS, I found that there aren't any.
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