Am Donnerstag, den 15.02.2018, 11:00 +0200 schrieb Ran Shalit:
> I actually asked about DMA, because I see that it is possible to send
> urb using DMA allocated buffers or not (coherent and non-coherent)
> usb_buffer_alloc().
> So, How can we actually know if I should use this API with a device or
> not ? I mean, is it always possible to use the coherent buffer with
> the device ?
Hi,
it is always possible to use usb_alloc_coherent() on a host.
But it is generally not sensible. It is for buffers to be reused
many times. In general use kmalloc() [once per buffer. That is a rule.
You must not share them.]
HTH
Oliver
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