Messages in this thread | | | Date | Wed, 3 Dec 2008 20:17:39 -0800 | From | Greg KH <> | Subject | Re: [PATCH 1/1] Userspace I/O (UIO): Add support for userspace DMA (corrected) |
| |
On Wed, Dec 03, 2008 at 05:51:30PM -0800, Edward Estabrook wrote: > From: Edward Estabrook <Edward_Estabrook@agilent.com> > > Here is a patch that adds the ability to dynamically allocate and use > coherent DMA > from userspace by extending the Userspace IO driver. This patch applies against > 2.6.28-rc6. > > The gist of this implementation is to overload uio's mmap > functionality to allocate > and map a new DMA region on demand. The bus-specific DMA address as returned by > dma_alloc_coherent is made available to userspace in the 1st long word > of the newly > created region (as well as through the conventional 'addr' file in sysfs). > > The kernel-api change is that passing an offset value of 0xFFFFF000UL > to the a uio > device's mmap operation will dynamically allocate a DMA region. This > cannot change/ > break existing behavior as the previous UIO code only allowed a maximum of 5 > mappings.
Odd formatting of your paragraphs :(
Anyway, what about 64bit processors? What happens if they try to use a valid address in this range?
Is this value always an "invalid" value for all arches that Linux runs on?
thanks,
greg k-h
| |