From: Christoph Hellwig <hch@lst.de>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
Greg KH <gregkh@linuxfoundation.org>,
Daniel Vetter <daniel@ffwll.ch>,
David Airlie <airlied@redhat.com>,
dri-devel <dri-devel@lists.freedesktop.org>,
USB list <linux-usb@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Regression: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices")
Date: Thu, 18 Feb 2021 16:24:25 +0100 [thread overview]
Message-ID: <20210218152425.GA19470@lst.de> (raw)
In-Reply-To: <ef51698a-cd93-47b3-b79f-8c86a4c215fc@suse.de>
On Thu, Feb 18, 2021 at 04:21:26PM +0100, Thomas Zimmermann wrote:
> Sure, it's at [1]. For udl, the dmabuf would need to be in system memory.
> The driver creates urbs from the framebuffer content and sends them to the
> device for displaying.
>
> My question is more: what's the best interface to do this? Is there example
> code somewhere?
URBs do point to system memory most of the time. I'm not a real USB
expert, but usb-storage or uas would be classic examples for drivers
that take arbitrary memory controller by another layer and do DMA to/from
that.
prev parent reply other threads:[~2021-02-18 16:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-18 14:56 Regression: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") Thomas Zimmermann
2021-02-18 14:56 ` Thomas Zimmermann
2021-02-18 15:07 ` Christoph Hellwig
2021-02-18 15:21 ` Thomas Zimmermann
2021-02-18 15:21 ` Thomas Zimmermann
2021-02-18 15:24 ` Christoph Hellwig [this message]
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