linux-kernel - Re: [PATCH 10/27] drivers/memory: don't check resource with devm_ioremap

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Date:	Tue, 23 Jul 2013 18:27:57 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Joe Perches <joe@...ches.com>
CC:	Wolfram Sang <wsa@...-dreams.de>, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH 10/27] drivers/memory: don't check resource with devm_ioremap_resource

On 07/23/2013 11:25 AM, Joe Perches wrote:
> On Tue, 2013-07-23 at 20:01 +0200, Wolfram Sang wrote:
>> devm_ioremap_resource does sanity checks on the given resource. No need to
>> duplicate this in the driver.
> 
> Hi Wolfram:
> 
> This is the first and only one of the patch series I looked at.
> 
>> diff --git a/drivers/memory/tegra20-mc.c b/drivers/memory/tegra20-mc.c
> []
>> @@ -218,8 +218,6 @@ static int tegra20_mc_probe(struct platform_device *pdev)
>>  		struct resource *res;
>>  
>>  		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
>> -		if (!res)
>> -			return -ENODEV;
>>  		mc->regs[i] = devm_ioremap_resource(&pdev->dev, res);
> 
> I'm not so sure this is appropriate.
> 
> devm_ioremap_resource returns ERR_PTR(-EINVAL) for
> null resource so this changes the return.

I think the exact return value is probably pretty arbitrary here.

> devm_ioremap_resource also emits a noisy dev_err
> message when resource is NULL.
> 
> It's a probe and before the message log would be silent
> but now there's a new dmesg.

I think those changes are fine, at least for this driver. It's a bug if
the required resources are missing, and having probe() actively point
out why it's failing can only be a good thing in my book.
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