From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755776AbaJWNin (ORCPT ); Thu, 23 Oct 2014 09:38:43 -0400 Received: from galahad.ideasonboard.com ([185.26.127.97]:43797 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751022AbaJWNim (ORCPT ); Thu, 23 Oct 2014 09:38:42 -0400 From: Laurent Pinchart To: Maxime Ripard Cc: dmaengine@vger.kernel.org, Vinod Koul , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Antoine =?ISO-8859-1?Q?T=E9nart?= , lars@metafoo.de, Russell King , Dan Williams Subject: Re: [PATCH v3 58/59] dmaengine: Add a warning for drivers not using the generic slave caps retrieval Date: Thu, 23 Oct 2014 16:38:39 +0300 Message-ID: <4793064.0sBqs1vkQS@avalon> User-Agent: KMail/4.12.5 (Linux/3.14.14-gentoo; KDE/4.12.5; x86_64; ; ) In-Reply-To: <20141023131933.GO7893@lukather> References: <1413992653-21963-1-git-send-email-maxime.ripard@free-electrons.com> <2006617.Jsn4xl9O1U@avalon> <20141023131933.GO7893@lukather> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Maxime, On Thursday 23 October 2014 15:19:33 Maxime Ripard wrote: > On Thu, Oct 23, 2014 at 12:21:31AM +0300, Laurent Pinchart wrote: > > Hi Maxime, > > > > Thank you for the patch. > > > > On Wednesday 22 October 2014 17:44:12 Maxime Ripard wrote: > > > For the slave caps retrieval to be really useful, most drivers need to > > > implement it. > > > > > > Hence, we need to be slightly more aggressive, and trigger a warning at > > > registration time for drivers that don't fill their caps infos in order > > > to > > > encourage them to implement it. > > > > > > Signed-off-by: Maxime Ripard > > > --- > > > > > > drivers/dma/dmaengine.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c > > > index 98e9431f85ec..4e18981b16bd 100644 > > > --- a/drivers/dma/dmaengine.c > > > +++ b/drivers/dma/dmaengine.c > > > @@ -827,6 +827,9 @@ int dma_async_device_register(struct dma_device > > > *device) BUG_ON(!device->device_issue_pending); > > > > > > BUG_ON(!device->dev); > > > > > > + WARN(dma_has_cap(DMA_SLAVE, device->cap_mask) && > > > !device->generic_slave_caps, > > > + "this driver doesn't support generic slave capabilities > > > reporting\n"); > > > + > > > > This might be slightly too aggressive. > > I disagree with that. If we want at some point to have the drivers > implement it, we should be aggressive (and note that we don't break > anything, the driver will still work as it used to). I meant too aggressive given the possibility that a driver might need its own implementation if not all channels have the same capability. > > I agree with your previous comment on all DMA engine drivers > > returning the same capabilities for all channels, but it might not > > be true anymore in the future, in which case drivers will need to > > implement a custom slave caps function. We could delay support for > > that to when it's needed though. > > Actually, my next patch (59) is removing such possibility... And you > acked it ;) > > Is it still something we should be concerned about? Maybe not now, we can always add that possibility back in the future if needed. -- Regards, Laurent Pinchart