From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 03EFD6B002C for ; Wed, 12 Oct 2011 10:24:59 -0400 (EDT) Received: by bkbzs2 with SMTP id zs2so154976bkb.14 for ; Wed, 12 Oct 2011 07:24:57 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1318325033-32688-1-git-send-email-sumit.semwal@ti.com> <1318325033-32688-2-git-send-email-sumit.semwal@ti.com> Date: Wed, 12 Oct 2011 09:24:56 -0500 Message-ID: Subject: Re: [Linaro-mm-sig] [RFC 1/2] dma-buf: Introduce dma buffer sharing mechanism From: Rob Clark Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Dave Airlie Cc: Sumit Semwal , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linux@arm.linux.org.uk, arnd@arndb.de, jesse.barker@linaro.org, daniel@ffwll.ch On Wed, Oct 12, 2011 at 9:01 AM, Dave Airlie wrote: >> But then we'd need a different set of accessors for every different >> drm/v4l/etc driver, wouldn't we? > > Not any more different than you need for this, you just have a new > interface that you request a sw object from, > then mmap that object, and underneath it knows who owns it in the kernel. oh, ok, so you are talking about a kernel level interface, rather than userspace.. but I guess in this case I don't quite see the difference. It amounts to which fd you call mmap (or ioctl[*]) on.. If you use the dmabuf fd directly then you don't have to pass around a 2nd fd. [*] there is nothing stopping defining some dmabuf ioctls (such as for synchronization).. although the thinking was to keep it simple for first version of dmabuf BR, -R > mmap just feels wrong in this API, which is a buffer sharing API not a > buffer mapping API. > >> I guess if sharing a buffer between multiple drm devices, there is >> nothing stopping you from having some NOT_DMABUF_MMAPABLE flag you >> pass when the buffer is allocated, then you don't have to support >> dmabuf->mmap(), and instead mmap via device and use some sort of >> DRM_CPU_PREP/FINI ioctls for synchronization.. > > Or we could make a generic CPU accessor that we don't have to worry about. > > Dave. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org