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

[Jie Deng]

On 2021/7/2 17:58, Andy Shevchenko wrote:
> On Fri, Jul 02, 2021 at 04:46:47PM +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.
> >
> > 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.
> ...
>
> > +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.


> > +		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++.


> > +	}
> > +	return (fail ? -ETIMEDOUT : j);
> Redundant parentheses.


Will remove the parentheses.


> > +}
> ...
>
> > +	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.


> > +		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 !