[PATCH v4 virtio 01/10] virtio: allow caller to override device id and DMA mask

[Shannon Nelson <shannon.nelson@amd.com>]

To add a bit of flexibility with various virtio based devices, allow
the caller to specify a different device id and DMA mask.  This adds
fields to struct virtio_pci_modern_device to specify an override device
id check and a DMA mask.

int (*device_id_check)(struct pci_dev *pdev);
	If defined by the driver, this function will be called to check
	that the PCI device is the vendor's expected device, and will
	return the found device id to be stored in mdev->id.device.
	This allows vendors with alternative vendor device ids to use
	this library on their own device BAR.

u64 dma_mask;
	If defined by the driver, this mask will be used in a call to
	dma_set_mask_and_coherent() instead of the traditional
	DMA_BIT_MASK(64).  This allows limiting the DMA space on
	vendor devices with address limitations.

Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
---
 drivers/virtio/virtio_pci_modern_dev.c | 37 +++++++++++++++++---------
 include/linux/virtio_pci_modern.h      |  6 +++++
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index 869cb46bef96..1f2db76e8f91 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c
@@ -218,21 +218,29 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 	int err, common, isr, notify, device;
 	u32 notify_length;
 	u32 notify_offset;
+	int devid;
 
 	check_offsets();
 
-	/* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
-	if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
-		return -ENODEV;
-
-	if (pci_dev->device < 0x1040) {
-		/* Transitional devices: use the PCI subsystem device id as
-		 * virtio device id, same as legacy driver always did.
-		 */
-		mdev->id.device = pci_dev->subsystem_device;
+	if (mdev->device_id_check) {
+		devid = mdev->device_id_check(pci_dev);
+		if (devid < 0)
+			return devid;
+		mdev->id.device = devid;
 	} else {
-		/* Modern devices: simply use PCI device id, but start from 0x1040. */
-		mdev->id.device = pci_dev->device - 0x1040;
+		/* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
+		if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
+			return -ENODEV;
+
+		if (pci_dev->device < 0x1040) {
+			/* Transitional devices: use the PCI subsystem device id as
+			 * virtio device id, same as legacy driver always did.
+			 */
+			mdev->id.device = pci_dev->subsystem_device;
+		} else {
+			/* Modern devices: simply use PCI device id, but start from 0x1040. */
+			mdev->id.device = pci_dev->device - 0x1040;
+		}
 	}
 	mdev->id.vendor = pci_dev->subsystem_vendor;
 
@@ -260,7 +268,12 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 		return -EINVAL;
 	}
 
-	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
+	if (mdev->dma_mask)
+		err = dma_set_mask_and_coherent(&pci_dev->dev,
+						mdev->dma_mask);
+	else
+		err = dma_set_mask_and_coherent(&pci_dev->dev,
+						DMA_BIT_MASK(64));
 	if (err)
 		err = dma_set_mask_and_coherent(&pci_dev->dev,
 						DMA_BIT_MASK(32));
diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
index c4eeb79b0139..067ac1d789bc 100644
--- a/include/linux/virtio_pci_modern.h
+++ b/include/linux/virtio_pci_modern.h
@@ -38,6 +38,12 @@ struct virtio_pci_modern_device {
 	int modern_bars;
 
 	struct virtio_device_id id;
+
+	/* optional check for vendor virtio device, returns dev_id or -ERRNO */
+	int (*device_id_check)(struct pci_dev *pdev);
+
+	/* optional mask for devices with limited DMA space */
+	u64 dma_mask;
 };
 
 /*
-- 
2.17.1