From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH v3 2/5] tty: Introduce SER_RS485_SOFTWARE read-only flag for struct serial_rs485 Date: Thu, 12 Nov 2015 20:11:16 -0500 Message-ID: <564538B4.20402@hurleysoftware.com> References: <1447338836-8785-1-git-send-email-matwey@sai.msu.ru> <1447338836-8785-3-git-send-email-matwey@sai.msu.ru> <20151112195707.5e9cb1d8@lxorguk.ukuu.org.uk> <5644F4F2.2080408@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andy Shevchenko Cc: One Thousand Gnomes , "Matwey V. Kornilov" , Greg Kroah-Hartman , jslaby@suse.com, "linux-kernel@vger.kernel.org" , "linux-serial@vger.kernel.org" List-Id: linux-serial@vger.kernel.org On 11/12/2015 07:41 PM, Andy Shevchenko wrote: > On Thu, Nov 12, 2015 at 10:22 PM, Peter Hurley wrote: >> On 11/12/2015 02:57 PM, One Thousand Gnomes wrote: > >> An illustrative (kernel-space) example is the mess that is dmaengine_pause(). >> Some DMA implementations provide the means to stop and restart DMA without >> losing data and some DMA implementations do not. Unfortunately, some >> advertise they support dmaengine_pause() but only for lossy uses like audio. >> Because the api hides this, the query interface for pause support is >> useless. > > The DMA pause() call means only pause with possibility to resume. > There is a resume() call as well. Any driver which treats pause() as a > complete stop is buggy driver and should be fixed. How about pause _without_ the possibility to resume? https://groups.google.com/d/msg/linux.kernel/Abe0hfGcgsw/H0se55wC558J