Re: [Xen-devel] Contiguous DMAble memory in Dom0 user space linux process

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jan 20, 2010 at 01:10:24PM -0800, Kashmira. K. wrote:
> Hi Konard,
> 
> Thanks you for your reply. 
> 
> On the (non xen) linux system, the hardware was visible to the userspace app. 
> The PCI bars were mapped. So I do need to get the same functionality on xen 
> capable linux.
> 
> I'm still a newbie to the xen internals, but I was wondering if I could write 
> a simple linux kernel driver for a xen capable linux to do the following
> - Map the PCI address (BAR). 
> - Get contiguous memory.
> - Provide user space ioctl call to get the mapped PCI BAR
> - Provide user space ioctl to get pointer to the contiguous memory.
> 
> Will that work?

Sure. I would recommend you look at the 3w-xxxx.c driver for a simple
ioctl subsystem and how to get contiguous memory mapped in. For mmap 
functionality
hpet.c is pretty simple. Foremost, make sure you get a PDF copy of
"Understanding the Linux Kernel"  as that will answer a lot of your questions.

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