Re: Streaming acquisition from more than one subdevices

From: Bernd Porr <BerndPorr_at_f2s.com> · Date: Sun, 16 Jan 2005 19:41:15 +0000

I agree with Dave. There's no need to change anything right now. If you 
really want to stream to/from two devices then just register two 
different comedi devices in the device driver and associate them with 
comedi_config to two /dev/comediX devices.

And this works. Not only in theory.

/Bernd

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David Schleef wrote:
> On Fri, Jan 14, 2005 at 02:24:58PM +0000, Ian Abbott wrote:
> 
>>Frank Mori Hess wrote:
>>
>>>It is uncommon for a board's hardware to support more than 1 streaming 
>>>read and 1 write subdevice.  I definitely intend to remove the limitation 
>>>in comedi eventually though, maybe by having a device file for each 
>>>streaming subdevice using sysfs.
>>
>>Maybe the 'private_data' member of 'struct file' could be used to store 
>>information specific to a particular 'open' of the /dev/comediN device 
>>node.  Then the device node could be opened more than once and each file 
>>handle set to stream from a different subdevice.  In theory :-))
> 
> 
> It's a UNIX limitation.  Comedi jumps through some pretty
> nasty hoops already to be able to stream both input and output
> on the same device file.  There's no real reason for sticking
> to one device file, other than changing it would be incompatible.
> 
> 
> 
> dave...
> 
> 
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