Re: [PATCH v12] i2c: virtio: add a virtio i2c frontend driver

On 2021/7/2 17:58, Andy Shevchenko wrote:

On Fri, Jul 02, 2021 at 04:46:47PM +0800, Jie Deng wrote:

quoted

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.

The device specification can be found on
https://lists.oasis-open.org/archives/virtio-comment/202101/msg00008.html.

By following the specification, people may implement different
backend drivers to emulate different controllers according to
their needs.

...

quoted

+static int virtio_i2c_complete_reqs(struct virtqueue *vq,
+				    struct virtio_i2c_req *reqs,
+				    struct i2c_msg *msgs, int nr,
+				    bool fail)
+{
+	struct virtio_i2c_req *req;
+	bool failed = fail;
+	unsigned int len;
+	int i, j = 0;
+
+	for (i = 0; i < nr; i++) {
+		/* Detach the ith request from the vq */
+		req = virtqueue_get_buf(vq, &len);
+
+		/*
+		 * Condition (req && req == &reqs[i]) should always meet since
+		 * we have total nr requests in the vq.
+		 */
+		if (!failed && (WARN_ON(!(req && req == &reqs[i])) ||
+		    (req->in_hdr.status != VIRTIO_I2C_MSG_OK)))
+			failed = true;

...and after failed is true, we are continuing the loop, why?

Still need to continue to do some cleanup.

quoted

+		i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
+		if (!failed)
+			++j;

Besides better to read j++ the j itself can be renamed to something more
verbose.

Will change it to j++.

quoted

+	}
+	return (fail ? -ETIMEDOUT : j);

Redundant parentheses.

Will remove the parentheses.

quoted

+}

...

quoted

+	ret = virtio_i2c_send_reqs(vq, reqs, msgs, num);
+	if (ret != num) {
+		virtio_i2c_complete_reqs(vq, reqs, msgs, ret, true);

Below you check the returned code, here is not.

I will do some optimization here.

quoted

+		ret = 0;
+		goto err_free;
+	}
+
+	reinit_completion(&vi->completion);
+	virtqueue_kick(vq);
+
+	time_left = wait_for_completion_timeout(&vi->completion, adap->timeout);
+	if (!time_left)
+		dev_err(&adap->dev, "virtio i2c backend timeout.\n");
+
+	ret = virtio_i2c_complete_reqs(vq, reqs, msgs, num, !time_left);
+
+err_free:
+	kfree(reqs);
+	return ret;

+++ b/include/uapi/linux/virtio_i2c.h
+#include <linux/types.h>
+
+/* The bit 0 of the @virtio_i2c_out_hdr.@flags, used to group the requests */
+#define VIRTIO_I2C_FLAGS_FAIL_NEXT	BIT(0)

It's _BITUL() or so from linux/const.h.
https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/const.h#L28
You may not use internal definitions in UAPI headers.

Let's use this _BITUL() from linux/const.h instead. Thank you !


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