Isochronous USB transfers on RPI?
Hans Petter Selasky
hselasky at c2i.net
Wed Jan 16 12:18:00 UTC 2013
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
More information about the freebsd-arm
mailing list