On Sun, May 06, 2007 at 02:19:59PM +0200, Bodo Eggert wrote: > Since you ask for random thoughts: > > IO of data streams from or to a DAC/ADC is essentially what soundcards do. > I'm wondering if these cards are similar enough to use alsa, and if using > that interface would ease or hinder programming the driver.
I had a short look at ALSA and it looks like it is a little bit too focussed towards "normal" audio. For example, if follows an asynchronous model in the sense that an application can read/write to a buffer at any time, taken that the ringbuffer doesn't overflow. That's not enough for example for control applications; you need the option for real synchronous operation there. IMHO we need an API which offers - kernel ring buffers (to make it sure no data gets lost) - generic data types (streaming plain ADC values is just the simplest case; we also have for example streaming FPGA data containing preprocessed data sets) - optional timestamping for each sample - zero-copy from hardware into userspace memory, with DMA support - application notification every N samples (N >= 1) v4l2 may also be worth a look; but in the end I suppose they are all specialized sub-cases of what we'd need for fast DAQ. Robert -- Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de Pengutronix - Linux Solutions for Science and Industry Handelsregister: Amtsgericht Hildesheim, HRA 2686 Hannoversche Str. 2, 31134 Hildesheim, Germany Phone: +49-5121-206917-0 | Fax: +49-5121-206917-9 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
