linux-kernel - Re: [PATCH v4 1/2] clk: hisilicon: Use correct return value about hisi_reset

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Message-ID: <0936ce03-935d-d863-0bd1-a005ba1d40e0@loongson.cn>
Date:   Fri, 29 May 2020 12:02:05 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH v4 1/2] clk: hisilicon: Use correct return value about
 hisi_reset_init()

On 05/29/2020 11:58 AM, Stephen Boyd wrote:
> Quoting Tiezhu Yang (2020-05-28 19:03:54)
>> On 05/29/2020 07:15 AM, Stephen Boyd wrote:
>>> Quoting Tiezhu Yang (2020-05-27 19:27:42)
>>>> On 05/28/2020 03:06 AM, Stephen Boyd wrote:
>>>>> Quoting Tiezhu Yang (2020-05-27 07:39:21)
>>>>>> The return value about hisi_reset_init() is not correct, fix it.
>>>>>>
>>>>>> Fixes: e9a2310fb689 ("reset: hisilicon: fix potential NULL pointer dereference")
>>>>> hisi_reset_init() returns NULL on error in that commit. This patch
>>>>> doesn't make sense.
>>>> Hi Stephen,
>>>>
>>>> The initial aim of this patch is to use correct return value about
>>>> hisi_reset_init(), maybe NULL is OK, but the return value in this
>>>> patch is more accurate.
>>> The implementation of hisi_reset_init() that I see is this:
>>>
>>>
>>>        struct hisi_reset_controller *rstc;
>>>
>>>        rstc = devm_kmalloc(&pdev->dev, sizeof(*rstc), GFP_KERNEL);
>>>        if (!rstc)
>>>                return NULL;
>>>
>>>        rstc->membase = devm_platform_ioremap_resource(pdev, 0);
>>>        if (IS_ERR(rstc->membase))
>>>                return NULL;
>>>
>>>        spin_lock_init(&rstc->lock);
>>>        rstc->rcdev.owner = THIS_MODULE;
>>>        rstc->rcdev.ops = &hisi_reset_ops;
>>>        rstc->rcdev.of_node = pdev->dev.of_node;
>>>        rstc->rcdev.of_reset_n_cells = 2;
>>>        rstc->rcdev.of_xlate = hisi_reset_of_xlate;
>>>        reset_controller_register(&rstc->rcdev);
>>>
>>>        return rstc;
>>>
>>> And that returns NULL on an error and a valid pointer on success.
>>> Changing the code to check the return value of hisi_reset_init() for an
>>> error pointer is simply wrong without updating hisi_reset_init() to
>>> return an error pointer on error. Where is the patch that changes
>>> hisi_reset_init() to return an error pointer?
>> Hi Stephen,
>>
>> Do you mean the following changes?
> Yes where is this change?

ERR_PTR(-ENOMEM) and ERR_CAST(rstc->membase)


  	rstc = devm_kmalloc(&pdev->dev, sizeof(*rstc), GFP_KERNEL);
  	if (!rstc)
- return NULL;
+ return ERR_PTR(-ENOMEM);
  
  	rstc->membase = devm_platform_ioremap_resource(pdev, 0);
  	if (IS_ERR(rstc->membase))
- return NULL;
+ return ERR_CAST(rstc->membase);