From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753528AbbHUIar (ORCPT ); Fri, 21 Aug 2015 04:30:47 -0400 Received: from mga14.intel.com ([192.55.52.115]:33569 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752217AbbHUIam (ORCPT ); Fri, 21 Aug 2015 04:30:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,720,1432623600"; d="scan'208";a="772985875" Date: Fri, 21 Aug 2015 14:02:45 +0530 From: Vinod Koul To: Sebastian Andrzej Siewior Cc: Russell King - ARM Linux , peter@hurleysoftware.com, Dan Williams , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, nsekhar@ti.com, linux-omap@vger.kernel.org, linux-serial@vger.kernel.org, john.ogness@linutronix.de, Peter Ujfalusi Subject: Re: [PATCH 2/3] dma: add __must_check annotation for dmaengine_pause() Message-ID: <20150821083245.GM13546@localhost> References: <1438977619-15488-1-git-send-email-bigeasy@linutronix.de> <1438977619-15488-3-git-send-email-bigeasy@linutronix.de> <20150811095852.GW11789@localhost> <20150811100617.GD7576@n2100.arm.linux.org.uk> <55C9EBD5.3090203@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55C9EBD5.3090203@linutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 11, 2015 at 02:34:29PM +0200, Sebastian Andrzej Siewior wrote: > On 08/11/2015 12:06 PM, Russell King - ARM Linux wrote: > > I think what people need to learn is that an API in the kernel which > > returns an int _can_ fail - it returns an int so it _can_ return an > > error code. If it _can_ return an error code, there _will_ be > > implementations which _do_. > > > > If you don't check the return code, either your code doesn't care whether > > the function was successful or not, or you're playing with fire. This is > > a prime example of playing with fire. > > > > Let's leave the crappy userspace laziness with regard to error checking > > to userspace, and keep it out of the kernel. > > > > Yes, the DMA engine capabilities may not be sufficient to describe every > > detail of DMA engines, but that's absolutely no reason to skimp on error > > checking. Had there been some kind of error checking at the site, this > > problem would have been spotted before the 8250-omap driver was merged. > > Let me disable RX-DMA in 8250-omap code and push that stable. Then we > won't need a special annotation for pause support because it remains > off and is currently about one user. I browsed each driver in > drivers/dma each one which does support pause supports it and all of > them implement it unconditionally (ipu_idmac grabs a mutex first but > this is another story). > Adding error checking to 8250-omap like I have it in #1 and disabling > RX-DMA in case pause fails looks be reasonable since there is nothing > else that can be done I guess. > Once we have the missing piece in omap-dma the RX-DMA can be enabled in > 8250-omap. > Does this sound like a plan we can agree on? Yes sounds good to me.. -- ~Vinod