Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755838AbbLAJsJ (ORCPT ); Tue, 1 Dec 2015 04:48:09 -0500 Received: from comal.ext.ti.com ([198.47.26.152]:36912 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754181AbbLAJsC (ORCPT ); Tue, 1 Dec 2015 04:48:02 -0500 Subject: Re: [RFC v02 01/15] dmaengine: core: Allow NULL mask pointer in __dma_device_satisfies_mask() To: Andy Shevchenko References: <1448891145-10766-1-git-send-email-peter.ujfalusi@ti.com> <1448891145-10766-2-git-send-email-peter.ujfalusi@ti.com> CC: Vinod Koul , Arnd Bergmann , "linux-kernel@vger.kernel.org" , dmaengine , Linux OMAP Mailing List , linux-arm Mailing List , "linux-mmc@vger.kernel.org" , Sekhar Nori , linux-spi From: Peter Ujfalusi X-Enigmail-Draft-Status: N1110 Message-ID: <565D6CB1.8030808@ti.com> Date: Tue, 1 Dec 2015 11:47:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2058 Lines: 63 On 11/30/2015 04:35 PM, Andy Shevchenko wrote: > On Mon, Nov 30, 2015 at 3:45 PM, Peter Ujfalusi wrote: >> Treat as true condition the case when the mask is NULL. > > What do you think about setting some default (all "on") mask when mask > is not supplied? Probably rephrasing the commit message to say that when the mask is NULL it means that the caller does not care about the capabilities of the dma device thus return with true in such a case. We could also drop this patch and in private_candidate() : - if (!__dma_device_satisfies_mask(dev, mask)) { + if (mask && !__dma_device_satisfies_mask(dev, mask)) { pr_debug("%s: wrong capabilities\n", __func__); return NULL; } > I don't know for sure but there might be cases when you don't want > literally *any* channel to satisfy. Or set DMA_SLAVE only in dma_request_chan()? What happens if we have cases when we are able to request channel for memcpy via dma_request_chan() (dedicated memcpy channel/DMA engine?) in that case we will have the SLAVE set, but not MEMCPY, or any other variation we do not know yet? >> >> Signed-off-by: Peter Ujfalusi >> --- >> drivers/dma/dmaengine.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c >> index daf54a39bcc7..52c3eee48e2e 100644 >> --- a/drivers/dma/dmaengine.c >> +++ b/drivers/dma/dmaengine.c >> @@ -184,6 +184,9 @@ __dma_device_satisfies_mask(struct dma_device *device, >> { >> dma_cap_mask_t has; >> >> + if (!want) >> + return true; >> + >> bitmap_and(has.bits, want->bits, device->cap_mask.bits, >> DMA_TX_TYPE_END); >> return bitmap_equal(want->bits, has.bits, DMA_TX_TYPE_END); >> -- >> 2.6.3 >> > > > -- Péter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/