Re: mmap(2)ping of pci_alloc_consistent() allocated buffers on 2.4 kernels question/help

[Arjan van de Ven <arjanv@redhat.com>]

On Fri, 2005-09-16 at 20:33 +0200, Martin Drab wrote:
> Hi,
> 
> can anyone explain me why it is not possible to mmap(2) a buffer 
> allocated in kernel by pci_alloc_consistent() to userspace on a 2.4 
> kernel?
> 
> In kernel PCI device initialization function I do something like:
> 
> ...
> kladdr = pci_alloc_consistent (dev, BUFSIZE, &baddr);
> ...
> 
> Then I send the physical address (i.e. the value of phaddr = __pa(kladdr)) 
> to the userspace application, and then when in the userspace I do 
> something like
> 
> ...
> fd = fopen ("/dev/mem", O_RDWR);
> buf = mmap (NULL, BUFSIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, phaddr);
> ...


yuch.
why don't you make your device have an mmap operation instead?
(the device node that you use to get your physical address to userspace
in the first place)

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