linux-kernel - Re: [PATCH 1/1] lib: devres: Add error information printing for __devm_ioremap

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Date:   Mon, 7 Jun 2021 16:33:03 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH 1/1] lib: devres: Add error information printing for
 __devm_ioremap_resource()



On 2021/6/7 16:15, Geert Uytterhoeven wrote:
> Hi Leizhen,
> 
> On Mon, Jun 7, 2021 at 9:11 AM Leizhen (ThunderTown)
> <thunder.leizhen@...wei.com> wrote:
>> On 2021/5/17 15:04, Geert Uytterhoeven wrote:
>>> On Wed, Apr 28, 2021 at 8:33 AM Zhen Lei <thunder.leizhen@...wei.com> wrote:
>>>> Ensure that all error handling branches print error information. In this
>>>> way, when this function fails, the upper-layer functions can directly
>>>> return an error code without missing debugging information. Otherwise,
>>>> the error message will be printed redundantly or missing.
>>>>
>>>> Fixes: 35bd8c07db2c ("devres: keep both device name and resource name in pretty name")
>>>> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
>>>
>>> Thanks for your patch, which is now commit 5c3e241f5246445d ("lib:
>>> devres: Add error information printing for __devm_ioremap_resource()")
>>> in driver-core-next.
>>>
>>>> --- a/lib/devres.c
>>>> +++ b/lib/devres.c
>>>> @@ -157,8 +157,10 @@ __devm_ioremap_resource(struct device *dev, const struct resource *res,
>>>>                                              dev_name(dev), res->name);
>>>>         else
>>>>                 pretty_name = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
>>>> -       if (!pretty_name)
>>>> +       if (!pretty_name) {
>>>> +               dev_err(dev, "can't generate pretty name for resource %pR\n", res);
>>>
>>> If the above fails, it is due to a memory allocation failure, and the
>>> memory allocation core will have already printed an error message.
>>> So there is no need to print a second message.
>>> Hence IMHO this commit should be reverted.
>>
>> If the memory allocation fails, only the 'size' is printed, but the start address of
>> the 'res' is not printed. So the printing here is not repeated. The start address is
>> the more critical help information.
> 
> Does that actually matter?
> What can the user or developer do to fix this problem, with the
> additional knowledge of the resource's start address?

Oh, you're right.

> 
>>>>                 return IOMEM_ERR_PTR(-ENOMEM);
>>>> +       }
>>>>
>>>>         if (!devm_request_mem_region(dev, res->start, size, pretty_name)) {
>>>>                 dev_err(dev, "can't request region for resource %pR\n", res);
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>