Re: documentation

[Guilhem Tardy <guilhem_tardy@yahoo.com>]

> > What is required from my part to support memory mapping from the driver
> > to the application? Would this be supported through the OSS compatibility
> > layer, too?
> 
> hmm...  mmap without dma?
> how do you transfer the data on buffer to hardware?

The card doesn't support DMA, yet. Data is transferred to/from the buffer by
the driver copying 32-bit chunks. Those buffers were allocated by the MMAP,
today through the V4Lv2 API (this is an audio+video card).

> the copy and silence ops are called when write() is called (more
> exactly on alsa it's ioctl) - the thread writing to the device does
> actually work like DMA.  on mmap mode, there is no such one.  so you
> need an extra thread (or if it's not too heavy then tasklet might be
> available) anyway.

Having checked the brief documentation you referred to
(http://www.alsa-project.org/alsa-doc/alsa-lib/), I guess using the direct
audio buffer to communicate with the device means DMA+MMAP. I would like to do
the same thing, but have the driver actually copy data to/from the device. What
do you call "mmap mode" above?

Is there any other documentation more specific to driver development?

Guilhem.


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