From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 01 Sep 2020 11:06:17 +0000
Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT
Message-Id: <20200901110617.GA13232@lst.de>
List-Id: <linux-ia64.vger.kernel.org>
References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <CAAFQd5COLxjydDYrfx47ht8tj-aNPiaVnC+WyQA7nvpW4gs=ww@mail.gmail.com> <20200819135454.GA17098@lst.de> <CAAFQd5BuXP7t3d-Rwft85j=KTyXq7y4s24mQxLr=VoY9krEGZw@mail.gmail.com> <20200820044347.GA4533@lst.de> <20200820052004.GA5305@lst.de> <CAAFQd5CFiA2WBaaPQ9ezvMjYZfNw37c42UEy9Pk7kJyCi1mLzQ@mail.gmail.com> <20200820165407.GD12693@lst.de> <CAAFQd5D=NzgjosB51-O_cH27a8V6CPgCfaPSfHHz7nKJPbazgg@mail.gmail.com>
In-Reply-To: <CAAFQd5D=NzgjosB51-O_cH27a8V6CPgCfaPSfHHz7nKJPbazgg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: Tomasz Figa <tfiga@chromium.org>
Cc: Christoph Hellwig <hch@lst.de>, alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List <linux-doc@vger.kernel.org>, nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, linux-mips@vger.kernel.org, "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>, linux-mm@kvack.org, linux-samsung-soc <linux-samsung-soc@vger.kernel.org>, Joonyoung Shim <jy0922.shim@samsung.com>, linux-scsi@vger.kernel.org, Kyungmin Park <kyungmin.park@samsung.com>, Ben Skeggs <bskeggs@redhat.com>, Matt Porter <mporter@kernel.crashing.org>, Linux Media Mailing List <linux-media@vger.kernel.org>, Tom Lendacky <thomas.lendacky@amd.com>, Pawel Osciak <pawel@osciak.com>, Mauro Carvalho Chehab <mchehab@kernel.org>, "list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>, Joerg
        Roedel <joro@8bytes.org>," <linux-arm-kernel@lists.infradead.org>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim <sw0312.kim@samsung.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>, Joerg
        Roedel <joro@8bytes.org>," <iommu@lists.linux-foundation.org>

On Thu, Aug 20, 2020 at 07:33:48PM +0200, Tomasz Figa wrote:
> > It wasn't meant to be too insulting, but I found this out when trying
> > to figure out how to just disable it.  But it also ends up using
> > the actual dma attr flags for it's own consistency checks, so just
> > not setting the flag did not turn out to work that easily.
> >
> 
> Yes, sadly the videobuf2 ended up becoming quite counterintuitive
> after growing for the long years and that is reflected in the design
> of this feature as well. I think we need to do something about it.

So I'm about to respin the series and wonder how we should proceed.
I've failed to come up with a clean patch to keep the flag and make
it a no-op.  Can you or your team give it a spin?

Also I wonder if the flag should be renamed from NON_CONSISTENT
to NON_COHERENT - the consistent thing is a weird wart from the times
the old PCI DMA API that is mostly gone now.