linux-kernel - Re: [PATCH v2 02/53] dmaengine: Make channel allocation callbacks optional

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Date:	Thu, 16 Oct 2014 13:35:59 +0300
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	dmaengine@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Antoine Ténart <antoine@...e-electrons.com>,
	lars@...afoo.de, Russell King <linux@....linux.org.uk>,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 02/53] dmaengine: Make channel allocation callbacks optional

Hi Maxime,

Thank you for the patch.

On Thursday 16 October 2014 12:17:01 Maxime Ripard wrote:
> Nowadays, some drivers don't have anything in there channel allocation
> callbacks anymore.
> 
> Remove the BUG_ON if those callbacks aren't implemented, in order to allow
> drivers to not implement them.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> ---
>  drivers/dma/dmaengine.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index d5d30ed863ce..cfcb181b1184 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -817,8 +817,6 @@ int dma_async_device_register(struct dma_device *device)
> BUG_ON(dma_has_cap(DMA_INTERLEAVE, device->cap_mask) &&
>  		!device->device_prep_interleaved_dma);
> 
> -	BUG_ON(!device->device_alloc_chan_resources);
> -	BUG_ON(!device->device_free_chan_resources);
>  	BUG_ON(!device->device_tx_status);
>  	BUG_ON(!device->device_issue_pending);
>  	BUG_ON(!device->dev);

This will make dma_chan_get() or dma_chan_put() crash if the alloc or free 
functions are not implemented.

-- 
Regards,

Laurent Pinchart

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