linux-kernel - Re: [PATCH 15/15] mmc: host: sdhci-iproc: Tell the compiler that ACPI functions may not be used

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Date:   Thu, 2 Jul 2020 13:49:34 -0700
From:   Scott Branden <scott.branden@...adcom.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     ulf.hansson@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 15/15] mmc: host: sdhci-iproc: Tell the compiler that ACPI
 functions may not be used



On 2020-07-02 1:13 p.m., Lee Jones wrote:
> On Thu, 02 Jul 2020, Scott Branden wrote:
>
>> Hi Lee,
>>
>> On 2020-07-01 5:47 a.m., Lee Jones wrote:
>>> ... as is the case when !CONFIG_ACPI.
>>>
>>> Fixes the following W=1 kernel build warning:
>>>
>>>    mmc/host/sdhci-iproc.c:297:36: warning: ‘sdhci_iproc_acpi_ids’ defined but not used [-Wunused-const-variable=]
>>>
>>> Cc: Adrian Hunter <adrian.hunter@...el.com>
>>> Cc: Ray Jui <rjui@...adcom.com>
>>> Cc: Scott Branden <sbranden@...adcom.com>
>>> Cc: bcm-kernel-feedback-list@...adcom.com
>>> Signed-off-by: Lee Jones <lee.jones@...aro.org>
>>> ---
>>>    drivers/mmc/host/sdhci-iproc.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci-iproc.c b/drivers/mmc/host/sdhci-iproc.c
>>> index 225603148d7de..9c7d130205edd 100644
>>> --- a/drivers/mmc/host/sdhci-iproc.c
>>> +++ b/drivers/mmc/host/sdhci-iproc.c
>>> @@ -294,7 +294,7 @@ static const struct of_device_id sdhci_iproc_of_match[] = {
>>>    };
>>>    MODULE_DEVICE_TABLE(of, sdhci_iproc_of_match);
>> Would it better to compile this in if CONFIG_ACPI is defined instead?
>> #if CONFIG_ACPI
> Literally can't win.
>
>   https://lore.kernel.org/linux-arm-kernel/CAGb2v66Ws4WNPZbOYQvikKoozj_2WjzS-Jq-o2VxT77=k0vODw@mail.gmail.com/
>
> Damned if we do, damned if we don't. ;)
This is very minor in this one change here, but it's just more bloat of 
things that really should be compiled out if they're not used.
I don't understand why __maybe_unused would be preferred approach - 
unless it is not linked in when it is not used?
>
>>> -static const struct acpi_device_id sdhci_iproc_acpi_ids[] = {
>>> +static const struct acpi_device_id __maybe_unused sdhci_iproc_acpi_ids[] = {
>>>    	{ .id = "BRCM5871", .driver_data = (kernel_ulong_t)&iproc_cygnus_data },
>>>    	{ .id = "BRCM5872", .driver_data = (kernel_ulong_t)&iproc_data },
>>>    	{ /* sentinel */ }