Date: Wed, 16 Jan 2013 13:19:17 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-arm@freebsd.org Cc: Jakob Alvermark <jakob@alvermark.net> Subject: Re: Isochronous USB transfers on RPI? Message-ID: <201301161319.17236.hselasky@c2i.net> In-Reply-To: <6BD0E5E4-3921-4F9B-9381-3813933670AE@alvermark.net> References: <6BD0E5E4-3921-4F9B-9381-3813933670AE@alvermark.net>
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On Wednesday 16 January 2013 10:25:38 Jakob Alvermark wrote: > Hi, > > Maybe this should go to the usb list, but it is probably relevant here as > well. I have been playing with the Pi for a while now and having great fun > with FreeBSD. Great work gonzo and others! > However, I'd like to use a webcam with it. I learned that USB webcams use > isochronous transfers and the DWC OTG driver doesn't fully implement it. > (If I read the commit logs correctly) > What is missing and how can I help? > Hi, The DWC OTG driver has not fully implemented isochronous. Using isochronous transfers will have a high CPU load impact, because 1000 IRQ's (FS) or 8000 IRQ's (HS) second will be needed to feed the FIFOs. However, if this is acceptable, code can be found in: sys/dev/usb/controller/dwc_otg.c --HPS
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