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

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Date:   Mon, 5 Jul 2021 14:21:52 +0800
From:   Jie Deng <jie.deng@...el.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-i2c@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, wsa@...nel.org,
        wsa+renesas@...g-engineering.com, mst@...hat.com, arnd@...db.de,
        jasowang@...hat.com, yu1.wang@...el.com, shuo.a.liu@...el.com,
        conghui.chen@...el.com, stefanha@...hat.com
Subject: Re: [PATCH v12] i2c: virtio: add a virtio i2c frontend driver


On 2021/7/5 10:43, Viresh Kumar wrote:
> On 02-07-21, 12:58, Andy Shevchenko wrote:
>> On Fri, Jul 02, 2021 at 04:46:47PM +0800, Jie Deng wrote:
>>> +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;
> Jie, you can actually get rid of this variable too. Jut rename fail to failed
> and everything shall work as you want.


Oh, You are not right. I just found we can't remove this variable. The 
"fail" and "failed" have different

meanings for this function. We need fail to return the result.


>>> +	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?
> Actually this function can be called with fail set to true. We proceed as we
> need to call i2c_put_dma_safe_msg_buf() for all buffers we allocated earlier.
>
>>> +		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.
>>
>>> +}