linux-kernel - Re: [PATCH v2] media: stm32-dcmi: Use dma_request_chan() instead dma_request_slave

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Date:   Tue, 7 Jan 2020 13:38:56 +0000
From:   Hugues FRUCHET <hugues.fruchet@...com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>
CC:     "vkoul@...nel.org" <vkoul@...nel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] media: stm32-dcmi: Use dma_request_chan() instead
 dma_request_slave_channel()

Acked-by: Hugues Fruchet <hugues.fruchet@...com>

On 1/7/20 12:52 PM, Peter Ujfalusi wrote:
> dma_request_slave_channel() is a wrapper on top of dma_request_chan()
> eating up the error code.
> 
> By using dma_request_chan() directly the driver can support deferred
> probing against DMA.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> ---
> Hi,
> 
> Changes since v1:
> - Do not print error for EPROBE_DEFER
> 
> Regards,
> Peter
> 
>   drivers/media/platform/stm32/stm32-dcmi.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
> index 9392e3409fba..b63ff8d636ce 100644
> --- a/drivers/media/platform/stm32/stm32-dcmi.c
> +++ b/drivers/media/platform/stm32/stm32-dcmi.c
> @@ -1910,10 +1910,13 @@ static int dcmi_probe(struct platform_device *pdev)
>   		return PTR_ERR(mclk);
>   	}
>   
> -	chan = dma_request_slave_channel(&pdev->dev, "tx");
> -	if (!chan) {
> -		dev_info(&pdev->dev, "Unable to request DMA channel, defer probing\n");
> -		return -EPROBE_DEFER;
> +	chan = dma_request_chan(&pdev->dev, "tx");
> +	if (IS_ERR(chan)) {
> +		ret = PTR_ERR(chan);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev,
> +				"Failed to request DMA channel: %d\n", ret);
> +		return ret;
>   	}
>   
>   	spin_lock_init(&dcmi->irqlock);
>