Re: [PATCH] ata: pata_cs5535: Fix W=1 warnings

[John Garry]

On 28/06/2022 09:59, Damien Le Moal wrote:
> On 6/27/22 22:12, John Garry wrote:
> > x86_64 allmodconfig build with W=1 gives these warnings:
> >
> > drivers/ata/pata_cs5535.c: In function ‘cs5535_set_piomode’:
> > drivers/ata/pata_cs5535.c:93:11: error: variable ‘dummy’ set but not used [-Werror=unused-but-set-variable]
> >    u32 reg, dummy;
> >             ^~~~~
> > drivers/ata/pata_cs5535.c: In function ‘cs5535_set_dmamode’:
> > drivers/ata/pata_cs5535.c:132:11: error: variable ‘dummy’ set but not used [-Werror=unused-but-set-variable]
> >    u32 reg, dummy;
> >             ^~~~~
> > cc1: all warnings being treated as errors
> >
> > Mark variables 'dummy' as "maybe unused" to satisfy when rdmsr() is
> > stubbed, which is the same as what we already do in pata_cs5536.c .
> >
> > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
>
> Looks good, but I wonder why I am not getting this warning. I always do
> W=1 and C=1 builds. I tried allmodconfig now and I am not getting the
> warning...

eh, I'm not sure why. It's the only driver in drivers/ata/ which gives 
such a problem.

I'm using gcc 9:
gcc version 9.3.1 20200406 [revision 
6db837a5288ee3ca5ec504fbd5a765817e556ac2] (SUSE Linux)

Then I cross-compiled from my arm64 machine (to x86) and still got it:
john@ubuntu:~/kernel-dev$ /usr/bin/x86_64-linux-gnu-gcc --version
x86_64-linux-gnu-gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0

> > diff --git a/drivers/ata/pata_cs5535.c b/drivers/ata/pata_cs5535.c
> > index 6725931f3c35..c2c3238ff84b 100644
> > --- a/drivers/ata/pata_cs5535.c
> > +++ b/drivers/ata/pata_cs5535.c
> > @@ -90,7 +90,7 @@ static void cs5535_set_piomode(struct ata_port *ap, struct ata_device *adev)
> >   	static const u16 pio_cmd_timings[5] = {
> >   		0xF7F4, 0x53F3, 0x13F1, 0x5131, 0x1131
> >   	};
> > -	u32 reg, dummy;
> > +	u32 reg, __maybe_unused dummy;
> >   	struct ata_device *pair = ata_dev_pair(adev);
> >   
> >   	int mode = adev->pio_mode - XFER_PIO_0;
> > @@ -129,7 +129,7 @@ static void cs5535_set_dmamode(struct ata_port *ap, struct ata_device *adev)
> >   	static const u32 mwdma_timings[3] = {
> >   		0x7F0FFFF3, 0x7F035352, 0x7F024241
> >   	};
> > -	u32 reg, dummy;
> > +	u32 reg, __maybe_unused dummy;
> >   	int mode = adev->dma_mode;
> >   
> >   	rdmsr(ATAC_CH0D0_DMA + 2 * adev->devno, reg, dummy);