linux-kernel - Re: [PATCH] spi: rockchip: fix warning of static check

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Message-ID: <56F141E7.5030303@mentor.com>
Date:	Tue, 22 Mar 2016 15:00:23 +0200
From:	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
To:	Shawn Lin <shawn.lin@...k-chips.com>,
	Mark Brown <broonie@...nel.org>
CC:	<linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>,
	Doug Anderson <dianders@...omium.org>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] spi: rockchip: fix warning of static check

On 22.03.2016 14:56, Vladimir Zapolskiy wrote:
> Hi Shawn,
> 
> On 22.03.2016 13:36, Shawn Lin wrote:
>> Let's improve the check with -EPROBE_DEFER, otherwise
>> we may pass on null pointer to PTR_ERR. That causes the
>> static checker warning: passing zero to 'PTR_ERR'.
>>
>> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
>> Cc: Doug Anderson <dianders@...omium.org>
>> Cc: Dan Carpenter <dan.carpenter@...cle.com>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>
>>  drivers/spi/spi-rockchip.c | 10 +++++++---
>>  1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
>> index bfeb0d4..2cb36d9 100644
>> --- a/drivers/spi/spi-rockchip.c
>> +++ b/drivers/spi/spi-rockchip.c
>> @@ -726,20 +726,24 @@ static int rockchip_spi_probe(struct platform_device *pdev)
>>  	rs->dma_tx.ch = dma_request_slave_channel(rs->dev, "tx");
>>  	if (IS_ERR_OR_NULL(rs->dma_tx.ch)) {
>>  		/* Check tx to see if we need defer probing driver */
>> -		if (PTR_ERR(rs->dma_tx.ch) == -EPROBE_DEFER) {
>> +		if (rs->dma_tx.ch == ERR_PTR(-EPROBE_DEFER)) {
> 
> won't it be easier to change dma_request_slave_channel() to
> dma_request_chan() or dma_request_slave_channel_reason() and replace strange
> IS_ERR_OR_NULL() check with IS_ERR() one?
> 
> AFAIU that's almost what has been suggested by Doug and it is a better
> fix than this one published.
> 
> At the moment check for IS_ERR_OR_NULL() is too aggressive and quite
> confusing, because dma_request_slave_channel() never returns NULL.

Sorry for a typo, never returns IS_ERR() of course.

>>  			ret = -EPROBE_DEFER;
>>  			goto err_get_fifo_len;
>>  		}
>>  		dev_warn(rs->dev, "Failed to request TX DMA channel\n");
>> +		rs->dma_tx.ch = NULL;
>>  	}
>>  
>>  	rs->dma_rx.ch = dma_request_slave_channel(rs->dev, "rx");
>> -	if (!rs->dma_rx.ch) {
>> -		if (rs->dma_tx.ch) {
>> +	if (IS_ERR_OR_NULL(rs->dma_rx.ch)) {
>> +		if (rs->dma_tx.ch == ERR_PTR(-EPROBE_DEFER)) {
> 
> Same as above.
> 
>>  			dma_release_channel(rs->dma_tx.ch);
>>  			rs->dma_tx.ch = NULL;
>> +			ret = -EPROBE_DEFER;
>> +			goto err_get_fifo_len;
>>  		}
>>  		dev_warn(rs->dev, "Failed to request RX DMA channel\n");
>> +		rs->dma_rx.ch = NULL;
>>  	}
>>  
>>  	if (rs->dma_tx.ch && rs->dma_rx.ch) {
>>
> 

--
With best wishes,
Vladimir