From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [RFC 04/42] drivers/dma: don't check resource with devm_ioremap_resource Date: Fri, 10 May 2013 10:35:32 -0600 Message-ID: <518D21D4.6000609@wwwdotorg.org> References: <1368173847-5661-1-git-send-email-wsa@the-dreams.de> <1368173847-5661-5-git-send-email-wsa@the-dreams.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1368173847-5661-5-git-send-email-wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Vinod Koul , Dan Williams , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org On 05/10/2013 02:16 AM, Wolfram Sang wrote: > devm_ioremap_resource does sanity checks on the given resource. No need to > duplicate this in the driver. > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c > res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > - if (!res) { > - dev_err(&pdev->dev, "No mem resource for DMA\n"); > - return -EINVAL; > - } > - > tdma->base_addr = devm_ioremap_resource(&pdev->dev, res); One issue here is that it's not obvious just from reading the code that's left behind that the "missing" error-checking of the platform_get_resource() return value is OK because devm_ioremap_resource() will check it "for us". Everyone now has to mentally maintain a list of exceptions where it's OK not to error-check. A similar situation exists for e.g. kzalloc already spewing an error when allocations fail, and so drivers don't need to print a diagnostic in that case, but it's helpful if they do in most other cases, but that's another issue. Would it be better to introduce a new devm_ioremap_pdev_resource(pdev, index) that replaced both those two API calls with a single one. That way, only the author/reader of the new devm_ioremap_pdev_resource() would have to remember that caveat, and a single comment could be added so people unfamiliar with the code remember, without duplicating the comment in every driver.