linux-kernel - Re: [PATCH] staging: rtl8723bs: Remove ACPI table declaration

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Date:   Tue, 25 Sep 2018 23:44:37 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8723bs: Remove ACPI table declaration

On Wed, Sep 26, 2018 at 08:22:45AM +0200, Greg Kroah-Hartman wrote:
> On Tue, Sep 25, 2018 at 10:39:10PM -0700, Nathan Chancellor wrote:
> > Clang warns that the acpi_id declaration is not going to be emitted
> > in the final assembly:
> > 
> > drivers/staging/rtl8723bs/os_dep/sdio_intf.c:25:36: warning: variable
> > 'acpi_ids' is not needed and will not be emitted
> > [-Wunneeded-internal-declaration]
> > static const struct acpi_device_id acpi_ids[] = {
> >                                    ^
> > 1 warning generated.
> > 
> > This is because it's marked as static const and it is not used anywhere
> > in this file. Doing a git grep on this driver for 'acpi' shows that this
> > declaration has been unused since the driver's initial induction. Remove
> > it since it's not doing anything.
> > 
> > Link: https://github.com/ClangBuiltLinux/linux/issues/169
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  drivers/staging/rtl8723bs/os_dep/sdio_intf.c | 6 ------
> >  1 file changed, 6 deletions(-)
> > 
> > diff --git a/drivers/staging/rtl8723bs/os_dep/sdio_intf.c b/drivers/staging/rtl8723bs/os_dep/sdio_intf.c
> > index 6d02904de63f..d473f9bd08c3 100644
> > --- a/drivers/staging/rtl8723bs/os_dep/sdio_intf.c
> > +++ b/drivers/staging/rtl8723bs/os_dep/sdio_intf.c
> > @@ -22,13 +22,7 @@ static const struct sdio_device_id sdio_ids[] =
> >  	{ SDIO_DEVICE(0x024c, 0xb723), },
> >  	{ /* end: all zeroes */				},
> >  };
> > -static const struct acpi_device_id acpi_ids[] = {
> > -	{"OBDA8723", 0x0000},
> > -	{}
> > -};
> > -
> >  MODULE_DEVICE_TABLE(sdio, sdio_ids);
> > -MODULE_DEVICE_TABLE(acpi, acpi_ids);
> 
> You just removed the ability for the driver to be automatically loaded
> if that acpi id is present.
> 

I am not sure I understand. Every instance of acpi_device_id that I
looked at in the kernel before sending this patch uses MODULE_DEVICE_TABLE
but then that acpi_device_id declaration is always used in the driver
definition either under the acpi_match_table member or ids member
depending on what type of driver it is. Should this one do that as well?
Is that even possible with an sdio driver? I apologize if I am not
making sense, I'm not super familiar with these interfaces.

I also read 'Documentation/acpi/enumeration.txt' which makes it seem
like the declaration needs to be added to the device definition as well.

> Not good :(
> 
> I think you need to fix up your scripts, this is valid code...
> 

No scripts here, just a human interpreting warnings manually.

> greg k-h

Thanks for the review,
Nathan