linux-kernel - Re: [PATCH v3 2/3] hwmon: xgene: Add hwmon driver

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Date:   Thu, 08 Sep 2016 11:47:59 +0100
From:   James Morse <james.morse@....com>
To:     Arnd Bergmann <arnd@...db.de>, Guenter Roeck <linux@...ck-us.net>
CC:     Hoan Tran <hotran@....com>, Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>,
        Rob Herring <robh+dt@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Ashwin Chaugule <ashwin.chaugule@...aro.org>,
        Duc Dang <dhdang@....com>, lho@....com,
        linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v3 2/3] hwmon: xgene: Add hwmon driver

Hi,

On 08/09/16 09:14, Arnd Bergmann wrote:
> On Wednesday, September 7, 2016 3:37:05 PM CEST Guenter Roeck wrote:
>> On Wed, Sep 07, 2016 at 11:41:44PM +0200, Arnd Bergmann wrote:
>>> On Thursday, July 21, 2016 1:55:56 PM CEST Hoan Tran wrote:
>>>> +               ctx->comm_base_addr = cppc_ss->base_address;
>>>> +               if (ctx->comm_base_addr) {
>>>> +                       ctx->pcc_comm_addr =
>>>> +                                       acpi_os_ioremap(ctx->comm_base_addr,
>>>> +                                                       cppc_ss->length);
>>>>
>>>
>>> This causes the arm64 allmodconfig build to fail now, according to
>>> kernelci:
>>>
>>>       1  ERROR: "memblock_is_memory" [drivers/hwmon/xgene-hwmon.ko] undefined!
>>>
>>> Should this perhaps call ioremap() or memremap() instead?
>>>
>> Hmmm ... almost sounds to me like blaming the messenger. e7cd190385d1 ("arm64:
>> mark reserved memblock regions explicitly in iomem") starts using a function
>> in acpi_os_ioremap() which is not exported. On top of that, memblock_is_memory()
>> is declared as __init_memblock, which makes me really uncomfortable.
>> If acpi_os_ioremap() must not be used by modules, and possibly only during
>> early (?) initialization, maybe its declaration should state those limitations ?
> 
> Ah, I didn't notice that. I guess both patches were correct individually and
> got added to linux-next around the same time but caused allmodconfig to blow up
> when used together.
> 
> Adding everyone who was involved in the memblock patch to Cc here, maybe one
> of them has an idea what the correct fix is. There are only two other drivers
> using acpi_os_ioremap() and one of them is x86-specific, so it's still likely
> that drivers are not actually supposed to use this symbol. Making
> acpi_os_ioremap() an exported function in arm64 would also work.

You could use acpi_os_map_iomem()/acpi_os_unmap_iomem() from acpi/acpi_io.h.
If there isn't an existing mapping these end up in acpi_os_ioremap(), and are
already EXPORT_SYMBOL_GPL().

(I'm still waiting for allmodconfig on linux-next to finish building)


Thanks,

James