Re: [PATCH net] macmace: Set platform device coherent_dma_mask
From: Finn Thain
Date: Wed May 09 2018 - 21:25:35 EST
On Thu, 3 May 2018, Christoph Hellwig wrote:
> On Thu, May 03, 2018 at 10:46:56AM +0200, Geert Uytterhoeven wrote:
> > Perhaps you can add a new helper
> > (platform_device_register_simple_dma()?) that takes the DMA mask, too?
> > With people setting the mask to kill the WARNING splat, this may
> > become more common.
> > struct platform_device_info already has a dma_mask field, but
> > platform_device_register_resndata() explicitly sets it to zero.
> Yes, that would be useful. The other assumption could be that platform
> devices always allow an all-0xff dma mask.
Could that have unintended side effects? The mask is presently unset by
default, and my worry would be that changing it may cause some drivers to
A quick grep turns up this in drivers/spi/spi-au1550.c for example,
if (pdev->dev.dma_mask == NULL)
dev_warn(&pdev->dev, "no dma mask\n");
hw->usedma = 1;
Also, if pdev.dev.dma_mask is to get a default value, shouldn't it use the
same default as dma_get_mask, to avoid unintended side effects?
static inline u64 dma_get_mask(struct device *dev)
if (dev && dev->dma_mask && *dev->dma_mask)