Arnd Bergmann wrote:
That's also not how it works: each device starts out with a 32-bit mask,
because that's what historically all PCI devices can do. If a device
is 64-bit DMA capable, it can extend the mask by passing DMA_BIT_MASK(64)
(or whatever it can support), and the platform code checks if that's
possible.
So if it's not possible, then dma_set_mask returns an error, and the
driver should try a smaller mask? Doesn't that mean that every driver
for a 64-bit device should do this:
for (i = 64; i >=32; i--) {
ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(i));
if (!ret)
break;
}
if (ret)
return ret;
Sure, this is overkill, but it seems to me that the driver does not
really know what mask is actually valid, so it has to find the largest
mask that works.
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the
Code Aurora Forum, hosted by The Linux Foundation.
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