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

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Date:   Tue, 28 Jun 2022 17:59:22 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>, s.shtylyov@....ru
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: pata_cs5535: Fix W=1 warnings

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@...wei.com>

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...

> 
> 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);


-- 
Damien Le Moal
Western Digital Research