Re: [PATCH 2/4] MIPS: lantiq: adds minimal dcdc driver

[Lars-Peter Clausen <lars@metafoo.de>]

On 08/08/2013 01:17 PM, Florian Fainelli wrote:
> 2013/8/8 Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>:
>> Hello.
>>
>>
>> On 08-08-2013 13:07, John Crispin wrote:
>>
>>> This driver so far only reads the core voltage.
>>
>>
>>> Signed-off-by: John Crispin <blogic@openwrt.org>
>>
>> [...]
>>
>>
>>> diff --git a/arch/mips/lantiq/xway/dcdc.c b/arch/mips/lantiq/xway/dcdc.c
>>> new file mode 100644
>>> index 0000000..6361c30
>>> --- /dev/null
>>> +++ b/arch/mips/lantiq/xway/dcdc.c
>>> @@ -0,0 +1,75 @@
>>
>> [...]
>>
>>> +static int dcdc_probe(struct platform_device *pdev)
>>> +{
>>> +       struct resource *res;
>>> +
>>> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>> +       if (!res) {
>>> +               dev_err(&pdev->dev, "Failed to get resource\n");
>>> +               return -ENOMEM;
>>> +       }
>>
>>
>>     You do not need to check this with devm_request_and_ioremap() or
>> devm_ioremap_resource().
>>
>>
>>> +
>>> +       /* remap dcdc register range */
>>> +       dcdc_membase = devm_request_and_ioremap(&pdev->dev, res);
>>
>>
>>     Use devm_ioremap_resource().
>>
>>
>>> +       if (!dcdc_membase) {
>>> +               dev_err(&pdev->dev, "Failed to remap resource\n");
>>
>>
>>     Error messages are already printed by devm_request_and_ioremap()
>> ordevm_ioremap_resource().
>>
>>> +               return -ENOMEM;
>>
>>
>>     -EADDRNOTAVAIL is the right code for devm_request_and_ioremap().
>
> This is the first time that I read this, lib/devres.c internal returns
> -ENOMEM when an ioremap() call fails (see devm_ioremap_resource),
> -EADDRNOTAVAIL really is for networking matter, this is not.
>

You shouldn't need worry about the return code in this case anyway. This is the 
correct pattern for situations like this:

res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(base))
	return PTR_ERR(base);

- Lars