linux-kernel - Re: [PATCH] arm64: acpi: Export symbol for acpi_os

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Date:   Tue, 30 May 2023 19:37:34 +0800
From:   "lihuisong (C)" <lihuisong@...wei.com>
To:     Sudeep Holla <sudeep.holla@....com>,
        Ard Biesheuvel <ardb@...nel.org>
CC:     Lorenzo Pieralisi <lorenzo.pieralisi@...aro.org>,
        <catalin.marinas@....com>, <will@...nel.org>,
        <rafael.j.wysocki@...el.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <anshuman.khandual@....com>,
        <wangkefeng.wang@...wei.com>, <liuyonglong@...wei.com>
Subject: Re: [PATCH] arm64: acpi: Export symbol for acpi_os_ioremap


在 2023/5/30 18:58, Sudeep Holla 写道:
> On Mon, May 29, 2023 at 03:31:12PM +0200, Ard Biesheuvel wrote:
>> On Fri, 26 May 2023 at 15:12, lihuisong (C) <lihuisong@...wei.com> wrote:
>>>
>>> 在 2023/5/26 20:39, Ard Biesheuvel 写道:
>>>> (cc Lorenzo)
>>>>
>>>> On Fri, 26 May 2023 at 14:20, Huisong Li <lihuisong@...wei.com> wrote:
>>>>> The driver who calls the acpi_os_ioremap() cannot be compiled if the 'M'
>>>>> is selected for the driver. The compiling log is as follows:
>>>>> -->
>>>>> MODPOST Module.symvers
>>>>> ERROR: modpost: "acpi_os_ioremap" [drivers/soc/hisilicon/xxx.ko] undefined!
>>>>> scripts/Makefile.modpost:136: recipe for target 'Module.symvers' failed
>>>>> make[1]: *** [Module.symvers] Error 1
>>>>>
>>>>> So this patch exports symbol for acpi_os_ioremap.
>>>>>
>>>> That driver does not exist in mainline.
>>> We have an uploading driver [1] that may use it.
>>>
>>> [1]
>>> https://patchwork.kernel.org/project/linux-soc/patch/20230522072211.8894-2-lihuisong@huawei.com/
>>>
>>>> Why does it need to use acpi_os_ioremap() instead of the ordinary
>>>> memremap/ioremap routines?
>>> This driver needs to ioremap the shared memory space of a PCC subspace.
>>> And @Sudeep suggested that we use this interface.
>>> It is suitable here.
>> I disagree. acpi_io_ioremap() is internal arch plumbing for the ACPI
>> subsystem. I don't see why we should use it here.
>>
> Yes. One reason I suggested this was in past firmware authors had mixed
> the memory allocated for PCC and using acpi_io_ioremap() made sense. But
> I hear you and it make sense to avoid it especially if the driver must
> know what type of memory it is and must be dealing with.
>
>> On arm64, acpi_os_ioremap() cross references the EFI memory map to
>> figure out whether a physical region is memory or device, but a driver
>> should already know that.
> Agreed.
Thank you. will drop this patch.
>