Re: [PATCH v5 07/14] PCI: Add driver dma ownership management

From: Bjorn Helgaas <helgaas@kernel.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Joerg Roedel <joro@8bytes.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Christoph Hellwig <hch@infradead.org>,
	Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	kvm@vger.kernel.org, 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>,
	Stuart Yoder <stuyoder@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Chaitanya Kulkarni <kch@nvidia.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 v5 07/14] PCI: Add driver dma ownership management
Date: Wed, 23 Feb 2022 12:00:56 -0600	[thread overview]
Message-ID: <20220223180056.GA140951@bhelgaas> (raw)
In-Reply-To: <20220104015644.2294354-8-baolu.lu@linux.intel.com>

In subject,

s/dma/DMA/ to match the other patches

On Tue, Jan 04, 2022 at 09:56:37AM +0800, Lu Baolu wrote:
> Multiple PCI 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.
> 
> The device driver may set a new flag (no_kernel_api_dma) to skip calling
> iommu_device_use_dma_api() during the binding process. For instance, the
> userspace framework drivers (vfio etc.) which need to manually claim
> their own dma ownership when assigning the device to userspace.

s/vfio/VFIO/ when used as an acronym (occurs in several patches)

> + * @no_kernel_api_dma: Device driver doesn't use kernel DMA API for DMA.
> + *		Drivers which don't require DMA or want to manually claim the
> + *		owner type (e.g. userspace driver frameworks) could set this
> + *		flag.

s/Drivers which/Drivers that/

>  static int pci_dma_configure(struct device *dev)
>  {
> +	struct pci_driver *driver = to_pci_driver(dev->driver);
>  	struct device *bridge;
>  	int ret = 0;
>  
> +	if (!driver->no_kernel_api_dma) {

Ugh.  Double negative, totally agree this needs a better name that
reverses the sense.  Every place you use it, you negate it again.

> +	if (ret && !driver->no_kernel_api_dma)
> +		iommu_device_unuse_dma_api(dev);

> +static void pci_dma_cleanup(struct device *dev)
> +{
> +	struct pci_driver *driver = to_pci_driver(dev->driver);
> +
> +	if (!driver->no_kernel_api_dma)
> +		iommu_device_unuse_dma_api(dev);