Re: can device drivers return non-ram via vm_ops->nopage?
From: Zwane Mwaikambo
Date: Sat Mar 20 2004 - 19:25:12 EST
On Sat, 20 Mar 2004, Russell King wrote:
> The issues are:
> 1. ALSA wants to mmap the buffer used to transfer data to/from the
> card into user space. This buffer may be direct-mapped RAM,
> memory allocated via dma_alloc_coherent(), an on-device buffer,
> or anything else.
> The user space mapping must likewise be DMA-coherent.
> Currently, ALSA just does virt_to_page() on whatever address it
> feels like in its nopage() function, which is obviously not
> acceptable for two out of the three specific cases above.
> 2. ALSA wants to _coherently_ share data between the kernel-side
> drivers, and user space ALSA library, mainly the DMA buffer
> head/tail pointers so both kernel space and user space knows
> when the buffer is full/empty.
Doesn't DRI also suffer from the same issues?
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