On 2020/9/4 12:06, Jason Wang wrote:
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 293e7a0..70c8e30 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -21,6 +21,17 @@ config I2C_ALI1535
This driver can also be built as a module. If so, the module
will be called i2c-ali1535.
+config I2C_VIRTIO
+ tristate "Virtio I2C Adapter"
+ depends on VIRTIO
I guess it should depend on some I2C module here.
The dependency of I2C is included in the Kconfig in its parent directory.
So there is nothing special to add here.
+struct virtio_i2c_msg {
+ struct virtio_i2c_hdr hdr;
+ char *buf;
+ u8 status;
Any reason for separating status out of virtio_i2c_hdr?
The status is not from i2c_msg. So I put it out of virtio_i2c_hdr.
+};
+
+/**
+ * struct virtio_i2c - virtio I2C data
+ * @vdev: virtio device for this controller
+ * @completion: completion of virtio I2C message
+ * @adap: I2C adapter for this controller
+ * @i2c_lock: lock for virtqueue processing
+ * @vq: the virtio virtqueue for communication
+ */
+struct virtio_i2c {
+ struct virtio_device *vdev;
+ struct completion completion;
+ struct i2c_adapter adap;
+ struct mutex i2c_lock;
+ struct virtqueue *vq;
+};
+
+static void virtio_i2c_msg_done(struct virtqueue *vq)
+{
+ struct virtio_i2c *vi = vq->vdev->priv;
+
+ complete(&vi->completion);
+}
+
+static int virtio_i2c_add_msg(struct virtqueue *vq,
+ struct virtio_i2c_msg *vmsg,
+ struct i2c_msg *msg)
+{
+ struct scatterlist *sgs[3], hdr, bout, bin, status;
+ int outcnt = 0, incnt = 0;
+
+ if (!msg->len)
+ return -EINVAL;
+
+ vmsg->hdr.addr = msg->addr;
+ vmsg->hdr.flags = msg->flags;
+ vmsg->hdr.len = msg->len;
Missing endian conversion?
You are right. Need conversion here.
+
+ vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL);
+ if (!vmsg->buf)
+ return -ENOMEM;
+
+ sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr));
+ sgs[outcnt++] = &hdr;
+ if (vmsg->hdr.flags & I2C_M_RD) {
+ sg_init_one(&bin, vmsg->buf, msg->len);
+ sgs[outcnt + incnt++] = &bin;
+ } else {
+ memcpy(vmsg->buf, msg->buf, msg->len);
+ sg_init_one(&bout, vmsg->buf, msg->len);
+ sgs[outcnt++] = &bout;
+ }
+ sg_init_one(&status, &vmsg->status, sizeof(vmsg->status));
+ sgs[outcnt + incnt++] = &status;
+
+ return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg, GFP_KERNEL);
+}
+
+static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg
*msgs, int num)
+{
+ struct virtio_i2c *vi = i2c_get_adapdata(adap);
+ struct virtio_i2c_msg *vmsg_o, *vmsg_i;
+ struct virtqueue *vq = vi->vq;
+ unsigned long time_left;
+ int len, i, ret = 0;
+
+ vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
+ if (!vmsg_o)
+ return -ENOMEM;
It looks to me we can avoid the allocation by embedding virtio_i2c_msg
into struct virtio_i2c;
Yeah... That's better. Thanks.
+
+ mutex_lock(&vi->i2c_lock);
+ vmsg_o->buf = NULL;
+ for (i = 0; i < num; i++) {
+ ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
+ if (ret) {
+ dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
+ goto err_unlock_free;
+ }
+
+ virtqueue_kick(vq);
+
+ time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
+ if (!time_left) {
+ dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n", i,
msgs[i].addr);
+ ret = i;
+ goto err_unlock_free;
+ }
+
+ vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
+ if (vmsg_i) {
+ /* vmsg_i should point to the same address with vmsg_o */
+ if (vmsg_i != vmsg_o) {
+ dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
+ i, vmsg_i->hdr.addr);
+ ret = i;
+ goto err_unlock_free;
+ }
Does this imply in order completion of i2c device? (E.g what happens
if multiple virtio i2c requests are submitted)
Btw, this always use a single descriptor once a time which makes me
suspect if a virtqueue(virtio) is really needed. It looks to me we can
utilize the virtqueue by submit the request in a batch.
I'm afraid not all physical devices support batch. I'd like to keep the
current design and consider
your suggestion as a possible optimization in the future.
Thanks.
+}
+
+static void virtio_i2c_del_vqs(struct virtio_device *vdev)
+{
+ vdev->config->reset(vdev);
Why need reset here?
Thanks
I'm following what other virtio drivers do.
They reset the devices before they clean up the queues.
+ vdev->config->del_vqs(vdev);
+}
+
+static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
+{
+ struct virtio_device *vdev = vi->vdev;
+
+ vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done,
"i2c-msg");
We've in the scope of ic2, so "msg" should be sufficient.
OK. Will change this name. Thanks.
+ return PTR_ERR_OR_ZERO(vi->vq);
