From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH v2] DMA: add help function to check whether dma controller registered Date: Thu, 22 Aug 2013 14:36:53 -0600 Message-ID: <52167665.90602@wwwdotorg.org> References: <1375423458-6868-1-git-send-email-rizhao@nvidia.com> <1377153781-18006-1-git-send-email-rizhao@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1377153781-18006-1-git-send-email-rizhao@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org To: Richard Zhao Cc: linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, vinod.koul@intel.com, djbw@fb.com, grant.likely@linaro.org, rob.herring@calxeda.com, devicetree@vger.kernel.org List-Id: linux-omap@vger.kernel.org On 08/22/2013 12:43 AM, Richard Zhao wrote: > DMA client device driver usually needs to know at probe time whether > dma controller has been registered to deffer probe. So add a help > function of_dma_check_controller. > > DMA request channel functions can also used to check it, but they > are usually called at open() time. This new function is almost identical to the existing of_dma_request_slave_channel(). Surely the code should be shared? But that said, I don't see any need for a new function; why can't drivers simply call of_dma_request_slave_channel() at probe time; from what I can see, that function doesn't actually request the channel, but rather simply looks it up, just like this one. The only difference is that of_dma_xlate() is also called, but that's just doing some data transformation, not actually recording channel ownership.