linux-kernel - Re: [RFCv2 1/2] virtio_console: Add support for DMA memory allocation

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Message-ID: <87zk4ye2jz.fsf@rustcorp.com.au>
Date:	Mon, 10 Sep 2012 17:23:52 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	sjur.brandeland@...ricsson.com,
	"Michael S . Tsirkin" <mst@...hat.com>
Cc:	Sjur Brændeland <sjurbren@...il.com>,
	Sjur Brændeland <sjur.brandeland@...ricsson.com>,
	Amit Shah <amit.shah@...hat.com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFCv2 1/2] virtio_console: Add support for DMA memory allocation

sjur.brandeland@...ricsson.com writes:

> From: Sjur Brændeland <sjur.brandeland@...ricsson.com>
>
> Add feature VIRTIO_CONSOLE_F_DMA_MEM. If the architecture has
> DMA support and this feature bit is set, the virtio data buffers
> will be allocated from DMA memory. If the device requests
> the feature VIRTIO_CONSOLE_F_DMA_MEM, but the architecture
> don't support DMA the driver's probe function will fail.
>
> This is needed for using virtio_console from the remoteproc
> framework.

Sorry for the back and forth, I've been pondering MST's points.

If we make a new dma-multiport device (eg. ID 11), how ugly is the code?

It would be a virtio console with DMA buffers and no console, just the
multiport stuff.  This would have no impact on the current spec for
virtio console.

Thanks,
Rusty.
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