Re: raw1394_start_iso_write ?
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From: Dan D. <dde...@co...> - 2001-02-09 16:45:59
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From: "Ken Offer" > Hi Andreas (et. al), > > I'm looking for an explanation of the parameters for this routine: > > int raw1394_start_iso_write(struct raw1394_handle *handle, > unsigned int channel, > unsigned int tag, > unsigned int sy, > unsigned int speed, > size_t length, > quadlet_t *data, > unsigned long rawtag); > > Please correct me if I'm wrong in these assertions: > > The "handle" parameter is returned from > raw1394_get_handle(). Yes > The "channel" parameter is the isochronous channel to use > during transmission. It ranges from 0 to 63? Yes > The tag parameter should be either: > > a. some register offset from CSR_REGISTER_BASE > (perhaps CSR_REGISTER_BASE+CSR_FCP_COMMAND?) No > b. some value which distinguishes the packet type from > other packet types? > > c. something else? Specific to the protocol. It can indicate the inclusion of CIP headers in the iso data packet. > The "sy" parameter is a complete mystery to me. Is it the > "Z" parameter that the 1394 Open Host Controller Interface > Specification references? No, the Z field is part of the DMA command descriptor. The Sy is specific to the protocol too. For example, DV does not use it; it always 0. Uncompressed video via Digital Camera sets this to 1 to indicate the start of a new frame. > The "speed" parameter should be 1 for 100Mbits/sec, 2 for > 200Mbits/sec and 3 for 400Mbits/sec (this I gleaned from the > 1394 Open Host Controller Interface Specification referenced > from the links page). Yes > The "length" parameter is the size of whatever data points to. Yes > The "data" parameter is: > > a. A pointer to a buffer of raw data to send Yes > b. A pointer to some "DMA data-structure/program" that is described > in the 1394 Open Host Controller Interface Specification. No > c. Something altogether different. > > d. An android serving on a starship in the 24th century. :) > > The "rawtag" parameter is another mystery. Is it the same value as > tag? Hmm... I don't recall that parameter. It is a full quadlet, so perhaps it allows one to completely format the iso header and access some reserved areas? > Any pointers you could offer would be greatly appreciated. > > -- > ______________________________________________________________ > Kenneth Ray Offer, II > Sr. Systems Analyst > Applied Research Laboratories/SDD > University of Texas at Austin > Office (512) 835-3859 FAX (512) 835-3259 > > Any opinions expressed above are mine and not necessarily > those of my employer. > > _______________________________________________ > mailing list Lin...@li... > http://lists.sourceforge.net/lists/listinfo/linux1394-user > |