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From: Tao Ren <>
To: Christoph Hellwig <>
Cc: Sasha Levin <>, Felipe Balbi <>,
	Ryan Chen <>,
	kernel test robot <>,,
	Konrad Rzeszutek Wilk <>,
	Andrew Jeffery <>,
	Greg Kroah-Hartman <>,
	Masahiro Yamada <>,, Tao Ren <>,,,
	Robin Murphy <>,
	Thomas Tai <>,
Subject: Re: [PATCH] usb: gadget: aspeed: set port_dev dma mask
Date: Sat, 27 Mar 2021 15:17:59 -0700	[thread overview]
Message-ID: <20210327221759.GA2997@taoren-ubuntu-R90MNF91> (raw)
In-Reply-To: <>

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?



  reply	other threads:[~2021-03-27 22:18 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-26  7:02 [PATCH] usb: gadget: aspeed: set port_dev dma mask rentao.bupt
2021-03-26 12:03 ` Robin Murphy
2021-03-26 12:05   ` Christoph Hellwig
2021-03-27 22:17     ` Tao Ren [this message]
2021-03-29  6:17       ` Christoph Hellwig
2021-03-31  3:47         ` Tao Ren

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