Messages in this thread |  | | From | Anders Torger <> | Subject | Re: How to transfer memory from PCI memory directly to user space safely and portable? | Date | Sun, 26 Nov 2000 16:36:38 +0100 |
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On Sun, 26 Nov 2000, you wrote: > On Sun, Nov 26, 2000 at 02:21:31PM +0100, Anders Torger wrote: > > memcpy_toio(iobase, user_space_src, count); > > I hope count isn't provided by userspace here ?
Fortunately, 'count' is controlled by the driver architecture (ALSA), and not the user.
> > 1. What happens if the user space memory is swapped to disk? Will > > verify_area() make sure that the memory is in physical RAM when it > > returns, or will it return -EFAULT, or will something even worse happen? > > On i386, you'll sleep implicitly waiting for the page fault to be handled; > in the generic case, anything could happen.
Do you know of an architecture that will not do like i386 in this case?
> > 2. Is this code really portable? I currently have an I386 architecture, > > and I could use copy_to/from_user on that instead, but that is not > > portable. Now, by using memcpy_to/fromio instead, is this code fully > > portable? > > No. It would be portable if you were using memcpy_fromuser_toio and it > existed.
Oh, I see. Again, I wonder, do you know of any architecture, currently supported by Linux, where my code would fail? It would be helpful to know.
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