On 2020/9/3 18:20, Andy Shevchenko wrote:
On Thu, Sep 03, 2020 at 01:34:45PM +0800, Jie Deng wrote:
Add an I2C bus driver for virtio para-virtualization.
The controller can be emulated by the backend driver in
any device model software by following the virtio protocol.
This driver communicates with the backend driver through a
virtio I2C message structure which includes following parts:
- Header: i2c_msg addr, flags, len.
- Data buffer: the pointer to the i2c msg data.
- Status: the processing result from the backend.
People may implement different backend drivers to emulate
different controllers according to their needs. A backend
example can be found in the device model of the open source
project ACRN. For more information, please refer to
https://projectacrn.org.
The virtio device ID 34 is used for this I2C adpter since IDs
before 34 have been reserved by other virtio devices.
Seems it's slightly different version to what I have reviewed internally.
My comments below. (I admit that some of them maybe new)
...
Yeah... Some new devices have been added into the virtio spec during
these days.
+/**
+ * struct virtio_i2c_hdr - the virtio I2C message header structure
+ * @addr: i2c_msg addr, the slave address
+ * @flags: i2c_msg flags
+ * @len: i2c_msg len
+ */
+struct virtio_i2c_hdr {
+ __virtio16 addr;
+ __virtio16 flags;
+ __virtio16 len;
+} __packed;
As Misha noticed and somewhere I saw 0-day reports these should be carefully
taken care of.
...
Sure. Will fix these.
+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;
+
+ 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;
break;
OK.
+ }
+
+ 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;
break;
And so on.
OK.
+ }
+
+ 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;
+ }
+ if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
+ dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
+ i, vmsg_i->hdr.addr, vmsg_i->status);
+ ret = i;
+ goto err_unlock_free;
+ }
+ if ((vmsg_i->hdr.flags & I2C_M_RD) && vmsg_i->hdr.len)
+ memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
+
+ kfree(vmsg_i->buf);
+ vmsg_i->buf = NULL;
+ }
+ reinit_completion(&vi->completion);
+ }
+ if (i == num)
+ ret = num;
And this conditional seems a dup of the for-loop successfully iterating over
entire queue.
You are right.
We may save several lines of code by using "Return (ret<0) ? ret : i" at
the end.
+err_unlock_free:
Redundant.
OK.
+ mutex_unlock(&vi->i2c_lock);
+ kfree(vmsg_o->buf);
+ kfree(vmsg_o);
+ return ret;
+}
...
+ vi->adap.timeout = HZ / 10;
+ Blank line.
OK.
+ ret = i2c_add_adapter(&vi->adap);
+ if (ret) {
+ dev_err(&vdev->dev, "failed to add virtio-i2c adapter.\n");
+ virtio_i2c_del_vqs(vdev);
Usually we do clean up followed by message.
I will change the order. Thank you.
+ }
+
+ return ret;
