Re: USB mass storage and ARM cache coherency

[Oliver Neukum]

Am Mittwoch, 17. Februar 2010 10:40:09 schrieb Benjamin Herrenschmidt:
> What bugs me here is that the dma_map_* operation should always
> be done at the lowest level, ie, the actual HCD driver, and thus
> it should be up to the HCD to decide whether to dma_map or not
> depending on whether it's going to do DMA or not. I haven't
> scrutinized USB lately but if that isn't the case and the dma_map_*
> operations are done behind your back by the USB core then that needs to
> be changed in a way or another, or hooked at least.

No problem here. USB core does the mapping only if the low-level driver
so requests. The only exception is in usb_buffer_alloc(), but that boils
down to dma_alloc_coherent()

	Regards
		Oliver
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