linux-kernel - Re: [PATCH] ALSA: cs4236: fix return check from call to pnp_port

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Date:   Thu, 11 Oct 2018 17:42:48 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Colin King" <colin.king@...onical.com>
Cc:     <alsa-devel@...a-project.org>, "Jaroslav Kysela" <perex@...ex.cz>,
        <kernel-janitors@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: cs4236: fix return check from call to pnp_port_start

On Wed, 10 Oct 2018 16:15:42 +0200,
Colin King wrote:
> 
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the return from pnp_port_start is being checked for validity
> by checking if it is greater or equal to zero, however, the return
> is unsigned and hence this check is always true.  An 0 return from
> pnp_port_start is actually an error, so fix the check by checking
> for validity when it is non-zero.

I guess you're confused between mpu_port[] and mpu_irq[]?
The check "mpu_irq[] >= 0" here is to see the module parameter value
from user.


thanks,

Takashi

> Detected by CoverityScan, CID#1468334 ("Unsigned compared to 0")
> 
> Fixes: a9824c868a2c ("[ALSA] Add CS4232 PnP BIOS support")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  sound/isa/cs423x/cs4236.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/isa/cs423x/cs4236.c b/sound/isa/cs423x/cs4236.c
> index 70559e59d18f..2211c39d2c18 100644
> --- a/sound/isa/cs423x/cs4236.c
> +++ b/sound/isa/cs423x/cs4236.c
> @@ -292,7 +292,7 @@ static int snd_cs423x_pnp_init_mpu(int dev, struct pnp_dev *pdev)
>  		mpu_irq[dev] = SNDRV_AUTO_IRQ;
>  	} else {
>  		mpu_port[dev] = pnp_port_start(pdev, 0);
> -		if (mpu_irq[dev] >= 0 &&
> +		if (!mpu_irq[dev] &&
>  		    pnp_irq_valid(pdev, 0) && pnp_irq(pdev, 0) >= 0) {
>  			mpu_irq[dev] = pnp_irq(pdev, 0);
>  		} else {
> -- 
> 2.17.1
> 
>