linux-kernel - Re: [PATCH] dma: at_hdmac: fix invalid remaining bytes detection

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Date:	Fri, 01 Aug 2014 18:08:55 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>
CC:	dmaengine@...r.kernel.org,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] dma: at_hdmac: fix invalid remaining bytes detection

Hello.

On 08/01/2014 02:03 PM, Alexandre Belloni wrote:

> Found using smatch:
> drivers/dma/at_hdmac.c:299 atc_get_bytes_left() warn: unsigned
> 'atchan->remain_desc' is never less than zero.

> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> ---
>   drivers/dma/at_hdmac.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)

> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index c13a3bb0f594..9ec84ee2fa25 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -294,14 +294,16 @@ static int atc_get_bytes_left(struct dma_chan *chan)
>   			ret = -EINVAL;
>   			goto out;
>   		}
> -		atchan->remain_desc -= (desc_cur->lli.ctrla & ATC_BTSIZE_MAX)
> -						<< (desc_first->tx_width);
> -		if (atchan->remain_desc < 0) {
> +
> +		count = (desc_cur->lli.ctrla & ATC_BTSIZE_MAX)
> +			<< (desc_first->tx_width);

    Parens not needed here.

[...]

WBR, Sergei

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