linux-kernel - Re: [PATCH] soc: kunpeng_hccs: fix some sparse warnings about incorrect type

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Message-Id: <2f47e7bd-fce3-4eb9-8166-d671b4eec828@app.fastmail.com>
Date:   Fri, 18 Aug 2023 03:57:48 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Huisong Li" <lihuisong@...wei.com>,
        "Arnd Bergmann" <arnd@...nel.org>
Cc:     linux-kernel@...r.kernel.org, soc@...nel.org,
        linux-arm-kernel@...ts.infradead.org, liuyonglong@...wei.com,
        xuwei5@...ilicon.com
Subject: Re: [PATCH] soc: kunpeng_hccs: fix some sparse warnings about incorrect type

On Fri, Aug 18, 2023, at 03:38, lihuisong (C) wrote:
> 在 2023/8/17 19:54, Arnd Bergmann 写道:
>> On Thu, Aug 17, 2023, at 03:37, lihuisong (C) wrote:
>>> 在 2023/8/16 21:17, Arnd Bergmann 写道:
>>>> On Tue, Aug 15, 2023, at 14:52, Huisong Li wrote:
>>>>> @@ -199,8 +200,8 @@ static int hccs_pcc_cmd_send(struct hccs_dev *hdev, u8 cmd,
>>>>>    			     struct hccs_desc *desc)
>>>>>    {
>>>>>    	struct hccs_mbox_client_info *cl_info = &hdev->cl_info;
>>>>> -	struct acpi_pcct_shared_memory *comm_base = cl_info->pcc_comm_addr;
>>>>> -	void *comm_space = (void *)(comm_base + 1);
>>>>> +	void __iomem *comm_space = (u8 *)cl_info->pcc_comm_addr +
>>>>> +					sizeof(struct acpi_pcct_shared_memory);
>>>>>    	struct hccs_fw_inner_head *fw_inner_head;
>>>>>    	struct acpi_pcct_shared_memory tmp = {0};
>>>>>    	u16 comm_space_size;
>>>> The cast still looks wrong, while both comm_space and ->pcc_comm_addr
>>>> are __iomem pointers, casting to a non-__iomem u8 pointer should
>>>> still produce that warning. I'd suggest casting to (u8 __iomem *)
>>>> or (void __iomem *), I assume you still need a cast here to get
>>>> the correct address.
>>> Thanks Arnd.
>>>
>>> You are right. So I modify it by dropping (u8 *) here in patch v2.
>>> Please take a look at this again.
>> Right, if pcc_comm_addr is already a u8 __iomem* or void*, that
>> works, I though the cast was needed since it points to a larger
>> object, which would throw off the calculation.
> This pcc_comm_addr is already defined "void __iomem *" type in patch v2.
> So that works well, right?

Yes, that works.

     Arnd