linux-kernel - Re: [PATCH] Staging: comedi: dt2815: remove set but not used variable 'hi'

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Date:   Mon, 6 Apr 2020 14:46:11 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     Wang Hai <wanghai38@...wei.com>, hsweeten@...ionengravers.com,
        gregkh@...uxfoundation.org
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: comedi: dt2815: remove set but not used variable
 'hi'

On 07/04/2020 13:59, Wang Hai wrote:
> Fixes gcc '-Wunused-but-set-variable' warning:
> 
> drivers/staging/comedi/drivers/dt2815.c: In function dt2815_ao_insn:
> drivers/staging/comedi/drivers/dt2815.c:91:19: warning: variable 'hi' set but not used [-Wunused-but-set-variable]
> 
> commit d6a929b7608a ("Staging: comedi: add dt2815 driver")
> involved this, remove it.
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Wang Hai <wanghai38@...wei.com>
> ---
>   drivers/staging/comedi/drivers/dt2815.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/comedi/drivers/dt2815.c b/drivers/staging/comedi/drivers/dt2815.c
> index 83026ba..bcf85ec 100644
> --- a/drivers/staging/comedi/drivers/dt2815.c
> +++ b/drivers/staging/comedi/drivers/dt2815.c
> @@ -88,12 +88,11 @@ static int dt2815_ao_insn(struct comedi_device *dev, struct comedi_subdevice *s,
>   	struct dt2815_private *devpriv = dev->private;
>   	int i;
>   	int chan = CR_CHAN(insn->chanspec);
> -	unsigned int lo, hi;
> +	unsigned int lo;
>   	int ret;
>   
>   	for (i = 0; i < insn->n; i++) {
>   		lo = ((data[i] & 0x0f) << 4) | (chan << 1) | 0x01;
> -		hi = (data[i] & 0xff0) >> 4;
>   
>   		ret = comedi_timeout(dev, s, insn, dt2815_ao_status, 0x00);
>   		if (ret)
> 

That 'hi' value should be written to the hardware, but the driver is 
broken.  I don't think this driver has ever been tested as working 
because it has never written the 'hi' value to the hardware!

I think I know how to fix it.  I'll send a patch.

-- 
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