Re: [PATCH] usb: gadget: aspeed: set port_dev dma mask

[Christoph Hellwig]

On Sat, Mar 27, 2021 at 03:17:59PM -0700, Tao Ren wrote:
> On Fri, Mar 26, 2021 at 01:05:26PM +0100, Christoph Hellwig wrote:
> > On Fri, Mar 26, 2021 at 12:03:03PM +0000, Robin Murphy wrote:
> > > This might happen to work out, but is far from correct. Just wait until you 
> > > try it on a platform where the USB controller is behind an IOMMU...
> > >
> > > It looks like something is more fundamentally wrong here - the device 
> > > passed to DMA API calls must be the actual hardware device performing the 
> > > DMA, which in USB-land I believe means the controller's sysdev.
> > 
> > The shiny new usb_intf_get_dma_device API provides the device to use.
> 
> Thanks Robin and Christoph for the feedback.
> 
> If I understand correctly, usb_intf_get_dma_device API is mainly for usb
> host drivers? I just found usb_gadget_map_request_by_dev API: does it
> make sense to replace usb_gadget_map_request with
> usb_gadget_map_request_by_dev so we can pass the actual DMA-capable
> hardware device (aspeed-vhub platform device) to the API?

Oh, right you're dealing with a gadget side driver.  Not sure about
the API there, I'll let the relevant maintainers chime in.