virtio: Add return code to get_features

Update the get_features function to return an error code instead of
directly returning the features. This prepares the codebase for
additional functionality that requires error handling.

Signed-off-by: Anirudh Srinivasan <asrinivasan@tenstorrent.com>

Author: asrinivasanTT

drivers/virtio/virtio.c

@@ -280,7 +280,9 @@ static int virtio_dev_probe(struct device *_d)
 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
 
 	/* Figure out what features the device supports. */
-	virtio_get_features(dev, device_features);
+	err = virtio_get_features(dev, device_features);
+	if (err)
+		goto err;
 
 	/* Figure out what features the driver supports. */
 	virtio_features_zero(driver_features);

drivers/virtio/virtio_mmio.c

@@ -91,19 +91,18 @@ struct virtio_mmio_device {
 
 /* Configuration interface */
 
-static u64 vm_get_features(struct virtio_device *vdev)
+static int vm_get_features(struct virtio_device *vdev, u64 *features_out)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
-	u64 features;
 
 	writel(1, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
-	features = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
-	features <<= 32;
+	*features_out = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
+	*features_out <<= 32;
 
 	writel(0, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
-	features |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
+	*features_out |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
 
-	return features;
+	return 0;
 }
 
 static int vm_finalize_features(struct virtio_device *vdev)

drivers/virtio/virtio_pci_legacy.c

@@ -18,13 +18,15 @@
 #include "virtio_pci_common.h"
 
 /* virtio config->get_features() implementation */
-static u64 vp_get_features(struct virtio_device *vdev)
+static int vp_get_features(struct virtio_device *vdev, u64 *features)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 
 	/* When someone needs more than 32 feature bits, we'll need to
 	 * steal a bit to indicate that the rest are somewhere else. */
-	return vp_legacy_get_features(&vp_dev->ldev);
+	*features = vp_legacy_get_features(&vp_dev->ldev);
+
+	return 0;
 }
 
 /* virtio config->finalize_features() implementation */

drivers/virtio/virtio_pci_modern.c

@@ -22,11 +22,11 @@
 
 #define VIRTIO_AVQ_SGS_MAX	4
 
-static void vp_get_features(struct virtio_device *vdev, u64 *features)
+static int vp_get_features(struct virtio_device *vdev, u64 *features)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 
-	vp_modern_get_extended_features(&vp_dev->mdev, features);
+	return vp_modern_get_extended_features(&vp_dev->mdev, features);
 }
 
 static int vp_avq_index(struct virtio_device *vdev, u16 *index, u16 *num)

drivers/virtio/virtio_pci_modern_dev.c

@@ -394,7 +394,7 @@ EXPORT_SYMBOL_GPL(vp_modern_remove);
  *
  * Fill the specified features array with the features read from the device
  */
-void vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
+int vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
 				     u64 *features)
 {
 	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
@@ -408,6 +408,8 @@ void vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
 		cur = vp_ioread32(&cfg->device_feature);
 		features[i >> 1] |= cur << (32 * (i & 1));
 	}
+
+    return 0;
 }
 EXPORT_SYMBOL_GPL(vp_modern_get_extended_features);
 

drivers/virtio/virtio_vdpa.c

@@ -378,12 +378,14 @@ static int virtio_vdpa_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
 	return err;
 }
 
-static u64 virtio_vdpa_get_features(struct virtio_device *vdev)
+static int virtio_vdpa_get_features(struct virtio_device *vdev, u64 *features)
 {
 	struct vdpa_device *vdpa = vd_get_vdpa(vdev);
 	const struct vdpa_config_ops *ops = vdpa->config;
 
-	return ops->get_device_features(vdpa);
+	*features = ops->get_device_features(vdpa);
+
+	return 0;
 }
 
 static int virtio_vdpa_finalize_features(struct virtio_device *vdev)

include/linux/virtio_config.h

@@ -124,8 +124,8 @@ struct virtio_config_ops {
 			struct irq_affinity *desc);
 	void (*del_vqs)(struct virtio_device *);
 	void (*synchronize_cbs)(struct virtio_device *);
-	u64 (*get_features)(struct virtio_device *vdev);
-	void (*get_extended_features)(struct virtio_device *vdev,
+	int (*get_features)(struct virtio_device *vdev, u64 *features);
+	int (*get_extended_features)(struct virtio_device *vdev,
 				      u64 *features);
 	int (*finalize_features)(struct virtio_device *vdev);
 	const char *(*bus_name)(struct virtio_device *vdev);
@@ -264,16 +264,16 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
 	return __virtio_test_bit(vdev, fbit);
 }
 
-static inline void virtio_get_features(struct virtio_device *vdev,
+static inline int virtio_get_features(struct virtio_device *vdev,
 				       u64 *features_out)
 {
+	virtio_features_zero(features_out);
+
 	if (vdev->config->get_extended_features) {
-		vdev->config->get_extended_features(vdev, features_out);
-		return;
+		return vdev->config->get_extended_features(vdev, features_out);
 	}
 
-	virtio_features_from_u64(features_out,
-		vdev->config->get_features(vdev));
+	return vdev->config->get_features(vdev, features_out);
 }
 
 /**

include/linux/virtio_pci_modern.h

@@ -99,7 +99,7 @@ static inline void vp_iowrite64_twopart(u64 val,
 void
 vp_modern_get_driver_extended_features(struct virtio_pci_modern_device *mdev,
 				       u64 *features);
-void vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
+int vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
 				     u64 *features);
 void vp_modern_set_extended_features(struct virtio_pci_modern_device *mdev,
 				     const u64 *features);