From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f54.google.com (mail-ee0-f54.google.com [74.125.83.54]) by kanga.kvack.org (Postfix) with ESMTP id 2F0AE6B0031 for ; Thu, 10 Apr 2014 08:24:06 -0400 (EDT) Received: by mail-ee0-f54.google.com with SMTP id d49so2978824eek.13 for ; Thu, 10 Apr 2014 05:24:03 -0700 (PDT) Received: from smtp-vbr11.xs4all.nl (smtp-vbr11.xs4all.nl. [194.109.24.31]) by mx.google.com with ESMTPS id x44si5823758eep.90.2014.04.10.05.24.01 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 10 Apr 2014 05:24:02 -0700 (PDT) Message-ID: <53468CFC.2060707@xs4all.nl> Date: Thu, 10 Apr 2014 14:22:20 +0200 From: Hans Verkuil MIME-Version: 1.0 Subject: Re: [RFC] Helper to abstract vma handling in media layer References: <1395085776-8626-1-git-send-email-jack@suse.cz> <53466C4A.2030107@samsung.com> <20140410103220.GB28404@quack.suse.cz> <53467B7E.5060408@xs4all.nl> <20140410121554.GC28404@quack.suse.cz> In-Reply-To: <20140410121554.GC28404@quack.suse.cz> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Marek Szyprowski , linux-mm@kvack.org, linux-media@vger.kernel.org, "linaro-mm-sig@lists.linaro.org" , 'Tomasz Stanislawski' , Laurent Pinchart On 04/10/14 14:15, Jan Kara wrote: > On Thu 10-04-14 13:07:42, Hans Verkuil wrote: >> On 04/10/14 12:32, Jan Kara wrote: >>> Hello, >>> >>> On Thu 10-04-14 12:02:50, Marek Szyprowski wrote: >>>> On 2014-03-17 20:49, Jan Kara wrote: >>>>> The following patch series is my first stab at abstracting vma handling >>>> >from the various media drivers. After this patch set drivers have to know >>>>> much less details about vmas, their types, and locking. My motivation for >>>>> the series is that I want to change get_user_pages() locking and I want >>>>> to handle subtle locking details in as few places as possible. >>>>> >>>>> The core of the series is the new helper get_vaddr_pfns() which is given a >>>>> virtual address and it fills in PFNs into provided array. If PFNs correspond to >>>>> normal pages it also grabs references to these pages. The difference from >>>>> get_user_pages() is that this function can also deal with pfnmap, mixed, and io >>>>> mappings which is what the media drivers need. >>>>> >>>>> The patches are just compile tested (since I don't have any of the hardware >>>>> I'm afraid I won't be able to do any more testing anyway) so please handle >>>>> with care. I'm grateful for any comments. >>>> >>>> Thanks for posting this series! I will check if it works with our >>>> hardware soon. This is something I wanted to introduce some time ago to >>>> simplify buffer handling in dma-buf, but I had no time to start working. >>> Thanks for having a look in the series. >>> >>>> However I would like to go even further with integration of your pfn >>>> vector idea. This structure looks like a best solution for a compact >>>> representation of the memory buffer, which should be considered by the >>>> hardware as contiguous (either contiguous in physical memory or mapped >>>> contiguously into dma address space by the respective iommu). As you >>>> already noticed it is widely used by graphics and video drivers. >>>> >>>> I would also like to add support for pfn vector directly to the >>>> dma-mapping subsystem. This can be done quite easily (even with a >>>> fallback for architectures which don't provide method for it). I will try >>>> to prepare rfc soon. This will finally remove the need for hacks in >>>> media/v4l2-core/videobuf2-dma-contig.c >>> That would be a worthwhile thing to do. When I was reading the code this >>> seemed like something which could be done but I delibrately avoided doing >>> more unification than necessary for my purposes as I don't have any >>> hardware to test and don't know all the subtleties in the code... BTW, is >>> there some way to test the drivers without the physical video HW? >> >> You can use the vivi driver (drivers/media/platform/vivi) for this. >> However, while the vivi driver can import dma buffers it cannot export >> them. If you want that, then you have to use this tree: >> >> http://git.linuxtv.org/cgit.cgi/hverkuil/media_tree.git/log/?h=vb2-part4 > Thanks for the pointer that looks good. I've also found > drivers/media/platform/mem2mem_testdev.c which seems to do even more > testing of the area I made changes to. So now I have to find some userspace > tool which can issue proper ioctls to setup and use the buffers and I can > start testing what I wrote :) Get the v4l-utils.git repository (http://git.linuxtv.org/cgit.cgi/v4l-utils.git/). You want the v4l2-ctl tool. Don't use the version supplied by your distro, that's often too old. 'v4l2-ctl --help-streaming' gives the available options for doing streaming. So simple capturing from vivi is 'v4l2-ctl --stream-mmap' or '--stream-user'. You can't test dmabuf unless you switch to the vb2-part4 branch of my tree. If you need help with testing it's easiest to contact me on the #v4l irc channel. Regards, Hans -- 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/ . Don't email: email@kvack.org