Re: [RFC PATCH v2 10/10] firmware: arm_scmi: Add virtio transport

On Fri, Nov 6, 2020 at 2:59 AM Peter Hilber
[off-list ref] wrote:

+static int scmi_vio_probe(struct virtio_device *vdev)
+{
+       struct device *dev = &vdev->dev;
+       struct scmi_vio_channel **vioch;
+       bool have_vq_rx;
+       int vq_cnt;
+       int i;
+       struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
+
+       vioch = devm_kcalloc(dev, VIRTIO_SCMI_VQ_MAX_CNT, sizeof(*vioch),
+                            GFP_KERNEL);
+       if (!vioch)
+               return -ENOMEM;
+
+       have_vq_rx = virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);
+       vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
+
+       for (i = 0; i < vq_cnt; i++) {
+               vioch[i] = devm_kzalloc(dev, sizeof(**vioch), GFP_KERNEL);
+               if (!vioch[i])
+                       return -ENOMEM;
+       }
+
+       if (have_vq_rx)
+               vioch[VIRTIO_SCMI_VQ_RX]->is_rx = true;
+
+       if (virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks,
+                           scmi_vio_vqueue_names, NULL)) {
+               dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt);
+               return -1;
+       }
+       dev_info(dev, "Found %d virtqueue(s)\n", vq_cnt);
+
+       for (i = 0; i < vq_cnt; i++) {
+               spin_lock_init(&vioch[i]->lock);
+               vioch[i]->vqueue = vqs[i];
+               vioch[i]->vqueue->priv = vioch[i];

The vqueue->priv field is used by core, you can't update it else
notifications won't work.

+       }
+
+       vdev->priv = vioch;
+
+       virtio_device_ready(vdev);
+
+       return 0;
+}

diff --git a/drivers/firmware/arm_scmi/virtio.c

b/drivers/firmware/arm_scmi/virtio.c
index f70aa72f34f1..b1af77341b30 100644

--- a/drivers/firmware/arm_scmi/virtio.c
+++ b/drivers/firmware/arm_scmi/virtio.c

@@ -80,7 +80,8 @@ static int scmi_vio_populate_vq_rx(struct

scmi_vio_channel *vioch,

 static void scmi_vio_complete_cb(struct virtqueue *vqueue)
 {
-       struct scmi_vio_channel *vioch = vqueue->priv;
+       struct scmi_vio_channel **_vioch = vqueue->vdev->priv;
+       struct scmi_vio_channel *vioch = _vioch[vqueue->index];
        unsigned long iflags;
        unsigned int length;

@@ -454,7 +455,6 @@ static int scmi_vio_probe(struct virtio_device *vdev)
        for (i = 0; i < vq_cnt; i++) {
                spin_lock_init(&vioch[i]->lock);
                vioch[i]->vqueue = vqs[i];
-               vioch[i]->vqueue->priv = vioch[i];
        }

        vdev->priv = vioch;

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