linux-kernel - Re: [RFC 04/42] drivers/dma: don't check resource with devm_ioremap

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Message-ID: <20130512182802.GA2922@katana>
Date:	Sun, 12 May 2013 20:28:07 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	linux-kernel@...r.kernel.org, Dan Williams <djbw@...com>,
	linux-tegra@...r.kernel.org
Subject: Re: [RFC 04/42] drivers/dma: don't check resource with
 devm_ioremap_resource

On Sun, May 12, 2013 at 09:34:40PM +0530, Vinod Koul wrote:
> On Fri, May 10, 2013 at 01:25:36PM -0600, Stephen Warren wrote:
> > On 05/10/2013 11:57 AM, Wolfram Sang wrote:
> > > On Fri, May 10, 2013 at 10:35:32AM -0600, Stephen Warren wrote:
> > >> 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.
> > > 
> > > My goal is to make not-checking the standard case with devm.
> > 
> > OK, if no parameters passed to any devm function every need to be
> > error-checked, that'll certainly be a bit easier to remember.
> Okay to remove the log message and move to devm_ but I dont agree with this
> patch not returning error above. We shouldnt supress the error..

The error will be reported because devm_ioremap_resource will return an
ERR_PTR.

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