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SubjectRe: [PATCH v12] i2c: virtio: add a virtio i2c frontend driver
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?

> + 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.

> + }

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

Redundant 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.

> + 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.

--
With Best Regards,
Andy Shevchenko


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