linux-kernel - Re: [PATCH] comedi: Fix driver module dependencies since HAS

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Message-ID: <191d21d7-e760-4b8d-a79f-8943329f7148@mev.co.uk>
Date:   Mon, 4 Sep 2023 13:22:57 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>,
        Arnd Bergmann <arnd@...nel.org>, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hartley Sweeten <hsweeten@...ionengravers.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] comedi: Fix driver module dependencies since HAS_IOPORT
 changes

On 04/09/2023 13:01, Ian Abbott wrote:
> On 04/09/2023 12:23, Niklas Schnelle wrote:
>> On Mon, 2023-09-04 at 11:10 +0100, Ian Abbott wrote:
>>> On 03/09/2023 16:49, Arnd Bergmann wrote:
>>>> On Fri, Sep 1, 2023, at 15:26, Ian Abbott wrote:
>>>>> Commit b5c75b68b7de ("comedi: add HAS_IOPORT dependencies") changed 
>>>>> the
>>>>> "select" directives to "depend on" directives for several config
>>>>> stanzas, but the options they depended on could not be selected,
>>>>> breaking previously selected options.
>>>>
>> ---8<---
>>>>> @@ -735,8 +738,8 @@ config COMEDI_ADL_PCI9111
>>>>>
>>>>>    config COMEDI_ADL_PCI9118
>>>>>        tristate "ADLink PCI-9118DG, PCI-9118HG, PCI-9118HR support"
>>>>> +    depends on HAS_IOPORT
>>>>>        depends on HAS_DMA
>>>>> -    depends on COMEDI_8254
>>>>>        help
>>>>>          Enable support for ADlink PCI-9118DG, PCI-9118HG, 
>>>>> PCI-9118HR cards
>>>>
>>>> I don't see why you'd remove the 'depends on COMEDI_8254' here
>>>> rather than turning it back into 'select' as it was originally.
>>>
>>> Oops!  That's an error on my part.  Thanks for catching it!
>>>
>>>>
>>>> It might be easier to revert the original patch, and then follow
>>>> up with a fixed version.
>>>
>>> Will any random config builds break in 6.5 stable if the original patch
>>> is reverted, or is the 'HAS_IOPORT' stuff still in preparation for
>>> future use?
>>>
>>
>> The patch that finally compile-time disables I/O port accesses as well
>> as a few others are still not merged. I was away for a few weeks and
>> also still have a few todos. I also and found a few things needed for
>> new changes. So no a revert will not break compiles or anything like
>> that.
> 
> Thanks for the confirmation.  Will it be safe to assume that anything 
> that selects ISA will also select HAS_IOPORT?  That is trivially the 
> case for arch/{alpha,arm,x86}; arch/mips explicitly selects HAS_IOPORT 
> if ISA is selected; arch/powerpc explicitly selects HAS_IOPORT if PCI is 
> selected and it is only possible to configure ISA if PPC_CHRP is 
> configured which selects FORCE_PCI and therefore selects PCI and 
> therefore selects HAS_IOPORT; arch/um does not select HAS_IOPORT and 
> although it has a 'config ISA', nothing appears to select it.  None of 
> the remaining arch/* have 'select ISA'.

Another quick question: Will dummy versions of request_region(), 
request_muxed_region() and release_region() (and the devm variants) 
exist in the future even if HAS_IOPORT is not selected?  If so, I guess 
any drivers that only use inb()/outb() and friends on successfully 
requested regions can safely replace inb()/outb() and friends with 
conditionally compiled wrappers.

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