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" as they are only ever written in
rdmsr() calls.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---
Differences to v1:
- Add RB tag (thanks!)
- Fix commit message

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);
-- 
2.35.3

On 6/29/22 18:18, 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" as they are only ever written in
> rdmsr() calls.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>

Updated for-5.20. Thanks !

> ---
> Differences to v1:
> - Add RB tag (thanks!)
> - Fix commit message
> 
> 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