Hello Alan, On 11.12.2014 20:36, Alan Stern wrote: > On Sun, 7 Dec 2014, Florian Echtler wrote: >> - Can I always use DMA on the USB side (for bulk transfers), or does >> this in any way require support from the USB device's hardware? (I'm >> guessing no, but a definite answer would be great.) > DMA requires hardware support in the USB host controller, not in the > USB device. Most current USB host controllers support DMA; only a few > of the oldest ones don't. thanks - good to know for sure. AFAICT if I want to transfer bulk messages using DMA, I can't just use kalloc and usb_bulk_msg, but need usb_alloc_coherent, usb_fill_bulk_urb and usb_submit_urb, correct? Also, can you suggest any documentation regarding the relation between videobuf2 and DMA? Thanks & best regards, Florian -- SENT FROM MY DEC VT50 TERMINAL
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