Re: [PATCH v3 04/18] driver core: platform: Add driver dma ownership management - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Stuart Yoder <stuyoder@gmail.com>,
	rafael@kernel.org, David Airlie <airlied@linux.ie>,
	linux-pci@vger.kernel.org,
	Thierry Reding <thierry.reding@gmail.com>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	Dmitry Osipenko <digetx@gmail.com>, Will Deacon <will@kernel.org>,
	Ashok Raj <ashok.raj@intel.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Christoph Hellwig <hch@infradead.org>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Kevin Tian <kevin.tian@intel.com>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	kvm@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Cornelia Huck <cohuck@redhat.com>,
	linux-kernel@vger.kernel.org, Li Yang <leoyang.li@nxp.com>,
	iommu@lists.linux-foundation.org,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v3 04/18] driver core: platform: Add driver dma ownership management
Date: Mon, 6 Dec 2021 08:54:47 +0100	[thread overview]
Message-ID: <Ya3Bx7uDEs3VzP2G@kroah.com> (raw)
In-Reply-To: <20211206015903.88687-5-baolu.lu@linux.intel.com>

On Mon, Dec 06, 2021 at 09:58:49AM +0800, Lu Baolu wrote:
> Multiple platform devices may be placed in the same IOMMU group because
> they cannot be isolated from each other. These devices must either be
> entirely under kernel control or userspace control, never a mixture. This
> checks and sets DMA ownership during driver binding, and release the
> ownership during driver unbinding.
> 
> Driver may set a new flag (suppress_auto_claim_dma_owner) to disable auto
> claiming DMA_OWNER_DMA_API ownership in the binding process. For instance,
> the userspace framework drivers (vfio etc.) which need to manually claim
> DMA_OWNER_PRIVATE_DOMAIN_USER when assigning a device to userspace.
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  include/linux/platform_device.h |  1 +
>  drivers/base/platform.c         | 30 +++++++++++++++++++++++++++++-
>  2 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
> index 4381c34af7e0..f3926be7582f 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -210,6 +210,7 @@ struct platform_driver {
>  	struct device_driver driver;
>  	const struct platform_device_id *id_table;
>  	bool prevent_deferred_probe;
> +	bool suppress_auto_claim_dma_owner;

We now have "prevent_" and "suppress_" as prefixes.  Why the difference?

What is wrong with "prevent_" for your new flag?

thanks,

greg k-h
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