On 2021/3/24 12:20, Viresh Kumar wrote:
On 23-03-21, 22:19, Jie Deng wrote:+static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) +{ + struct virtio_i2c *vi = i2c_get_adapdata(adap); + struct virtqueue *vq = vi->vq; + struct virtio_i2c_req *reqs; + unsigned long time_left; + int ret, nr; + + reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); + if (!reqs) + return -ENOMEM; + + mutex_lock(&vi->lock); + + ret = virtio_i2c_send_reqs(vq, reqs, msgs, num); + if (ret == 0) + goto err_unlock_free; + + nr = ret; + reinit_completion(&vi->completion); + virtqueue_kick(vq);Coming back to this again, what is the expectation from the other side for this ? I mean there is no obvious relation between the *msgs* which we are going to transfer (from the other side's or host's point of view). When should the host OS call its virtqueue_kick() counterpart ? Lemme give an example for this. Lets say that we need to transfer 3 messages here in this routine. What we did was we prepared virtqueue for all 3 messages together and then called virtqueue_kick(). Now if the other side (host) processes the first message and sends its reply (with virtqueue_kick() counterpart) before processing the other two messages, then it will end up calling virtio_i2c_msg_done() here. That will make us call virtio_i2c_complete_reqs(), while only the first messages is processed until now and so we will fail for the other two messages straight away. Should we send only 1 message from i2c-virtio linux driver and then wait for virtio_i2c_msg_done() to be called, before sending the next message to make sure it doesn't break ?
For simplicity, the original patch sent only 1 message to vq each time . I changed the way to send
a batch of requests in one time in order to improve efficiency according to Jason' suggestion.
As we discussed in the previous emails, the device can raise interrupt when some requests are still not completed
though this is not a good operation. In this case, the remaining requests in the vq will be ignored and
the i2c_algorithm. master_xfer will return 1 for your example. I will clarify this in the specs.
