On 2021/7/1 12:04, Viresh Kumar wrote:

On 01-07-21, 11:24, Jie Deng wrote:

quoted

Changes v10 -> v11
	- Remove vi->adap.class = I2C_CLASS_DEPRECATED.
	- Use #ifdef CONFIG_PM_SLEEP to replace the "__maybe_unused".
	- Remove "struct mutex lock" in "struct virtio_i2c".
	- Support zero-length request.
	- Remove unnecessary logs.
	- Remove vi->adap.timeout = HZ / 10, just use the default value.
	- Use BIT(0) to define VIRTIO_I2C_FLAGS_FAIL_NEXT.
	- Add the virtio_device index to adapter's naming mechanism.

Thanks Jie.

I hope you are going to send a fix for specification as well (for the
zero-length request) ?

Yes. I will send that fix once this patch get merged.

quoted

diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
+static int virtio_i2c_send_reqs(struct virtqueue *vq,
+				struct virtio_i2c_req *reqs,
+				struct i2c_msg *msgs, int nr)
+{
+	struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
+	int i, outcnt, incnt, err = 0;
+
+	for (i = 0; i < nr; i++) {
+		/*
+		 * Only 7-bit mode supported for this moment. For the address format,
+		 * Please check the Virtio I2C Specification.
+		 */
+		reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
+
+		if (i != nr - 1)
+			reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
+
+		outcnt = incnt = 0;
+		sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
+		sgs[outcnt++] = &out_hdr;
+
+		reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
+		if (!reqs[i].buf)
+			break;
+
+		sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);

The len can be zero here for zero-length transfers.

quoted

+
+		if (msgs[i].flags & I2C_M_RD)
+			sgs[outcnt + incnt++] = &msg_buf;
+		else
+			sgs[outcnt++] = &msg_buf;
+
+		sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
+		sgs[outcnt + incnt++] = &in_hdr;

Why are we still sending the msg_buf if the length is 0? Sending the
buffer makes sense if you have some data to send, but otherwise it is
just an extra sg element, which isn't required to be sent.

I think a fixed number of sgs will make things easier to develop backend.

If you prefer to parse the number of descriptors instead of using the 
msg length to

distinguish the zero-length request from other requests, I'm OK to set a 
limit.

if (!msgs[i].len) {
     sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);

     if (msgs[i].flags & I2C_M_RD)
         sgs[outcnt + incnt++] = &msg_buf;
     else
         sgs[outcnt++] = &msg_buf;
}

quoted

+#ifdef CONFIG_PM_SLEEP
+static int virtio_i2c_freeze(struct virtio_device *vdev)
+{
+	virtio_i2c_del_vqs(vdev);
+	return 0;
+}
+
+static int virtio_i2c_restore(struct virtio_device *vdev)
+{
+	return virtio_i2c_setup_vqs(vdev->priv);
+}
+#endif
+
+static struct virtio_driver virtio_i2c_driver = {
+	.id_table	= id_table,
+	.probe		= virtio_i2c_probe,
+	.remove		= virtio_i2c_remove,
+	.driver	= {
+		.name	= "i2c_virtio",
+	},
+#ifdef CONFIG_PM_SLEEP

You could avoid this pair of ifdef by creating dummy versions of below
routines for !CONFIG_PM_SLEEP case. Up to you.

Thank you. I'd like to keep the same.