From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Herrmann Subject: Re: [sur40] videobuf2 and/or DMA? Date: Thu, 11 Dec 2014 09:58:59 +0100 Message-ID: References: <54855856.3070207@butterbrot.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-ig0-f182.google.com ([209.85.213.182]:33288 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934168AbaLKI7A (ORCPT ); Thu, 11 Dec 2014 03:59:00 -0500 Received: by mail-ig0-f182.google.com with SMTP id hn15so4479273igb.9 for ; Thu, 11 Dec 2014 00:58:59 -0800 (PST) In-Reply-To: <54855856.3070207@butterbrot.org> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Florian Echtler Cc: linux-input , Oliver Neukum , Alan Stern , Hans de Goede Hi On Mon, Dec 8, 2014 at 8:50 AM, Florian Echtler wrote: > Hello everyone, > > I'm preparing to finally add support for the raw sensor video stream to > my driver for the SUR40 touchscreen. However, after an extensive amount > of Googling, I'm still not clear on the relationship between DMA > transfers, the USB core and the videobuf2 framework. > > Specifically, I'd like to know: > > - 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.) I thought the USB API hides that from you? Nevertheless, this is a question for linux-usb, not linux-input. I put some people on CC which work on both, HID and USB. Maybe they can help you. > - Regardless of the USB side of things, can I use the videobuf2 > framework without _having_ to use DMA? That way, I could get a basic > driver running without DMA and switch later when it's convenient and/or > the speedup is justified. This is definitely a question for linux-media. Thanks David