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    SubjectRe: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
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    On 2021/3/19 13:53, Viresh Kumar wrote:
    > On 16-03-21, 18:35, Jie Deng wrote:
    >> +++ 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++) {
    >> + if (!msgs[i].len)
    >> + break;
    >> +
    >> + /*
    >> + * 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);
    > You allocate a buffer here, lets see if they are freeing properly or not (I
    > remember that I gave same feedback earlier as well, but anyway).


    "MAY" allocate a buffer here.


    >
    >> + if (!reqs[i].buf)
    >> + break;
    >> +
    >> + 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;
    >> +
    >> + sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
    >> + sgs[outcnt + incnt++] = &in_hdr;
    >> +
    >> + err = virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL);
    >> + if (err < 0) {
    >> + pr_err("failed to add msg[%d] to virtqueue.\n", i);
    >> + i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
    > On failure here, you freed the buffers for request "i" but not others..


    Others still need to be sent and then be freed.


    >
    >> + break;
    >> + }
    >> + }
    >> +
    >> + return i;
    >> +}
    >> +
    >> +static int virtio_i2c_complete_reqs(struct virtqueue *vq,
    >> + struct virtio_i2c_req *reqs,
    >> + struct i2c_msg *msgs, int nr)
    >> +{
    >> + struct virtio_i2c_req *req;
    >> + unsigned int len;
    >> + int i, j;
    >> +
    >> + for (i = 0; i < nr; i++) {
    >> + req = virtqueue_get_buf(vq, &len);
    >> + if (!(req && req == &reqs[i])) {
    >> + pr_err("msg[%d]: addr=0x%x is out of order.\n", i, msgs[i].addr);
    >> + break;
    > Since you break here, what will happen to the buffer ? I thought
    > virtqueue_get_buf() will return a req only once and then you can't access it ?


    Will refine it along with the latter loop.


    >
    >> + }
    >> +
    >> + if (req->in_hdr.status != VIRTIO_I2C_MSG_OK) {
    >> + pr_err("msg[%d]: addr=0x%x backend error.\n", i, msgs[i].addr);
    >> + break;
    >> + }
    >> +
    >> + i2c_put_dma_safe_msg_buf(req->buf, &msgs[i], true);
    >> + }
    >> +
    >> + /*
    >> + * Detach all the used buffers from the vq and
    >> + * Release unused DMA safe buffer if any.
    >> + */
    >> + for (j = i; j < nr; j++) {
    >> + req = virtqueue_get_buf(vq, &len);
    >> + if (req)
    >> + i2c_put_dma_safe_msg_buf(req->buf, &msgs[j], false);
    > This will come in play only if something failed in the earlier loop ? Or my
    > understanding incorrect ? Also this should be merged with the above for loop
    > itself, it is just doing part of it.


    Will refine it along with the earlier loop.


    >
    >> + }
    >> +
    >> + return i;
    >> +}
    >> +
    >> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
    >> +{
    >> + struct virtio_i2c *vi = i2c_get_adapdata(adap);
    >> + struct virtqueue *vq = vi->vq;
    >> + struct virtio_i2c_req *reqs;
    >> + unsigned long time_left;
    >> + int ret, nr;
    >> +
    >> + reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
    >> + if (!reqs)
    >> + return -ENOMEM;
    >> +
    >> + mutex_lock(&vi->lock);
    >> +
    >> + ret = virtio_i2c_send_reqs(vq, reqs, msgs, num);
    >> + if (ret == 0)
    >> + goto err_unlock_free;
    >> +
    >> + nr = ret;
    >> + reinit_completion(&vi->completion);
    >> + virtqueue_kick(vq);
    >> +
    >> + time_left = wait_for_completion_timeout(&vi->completion, adap->timeout);
    >> + if (!time_left) {
    > On error here, we will surely not free the buffers, isn't it ?


    Right. Will fix it. Thank you.


    >> + dev_err(&adap->dev, "virtio i2c backend timeout.\n");
    >> + ret = -ETIMEDOUT;
    >> + goto err_unlock_free;
    >> + }
    >> +
    >> + ret = virtio_i2c_complete_reqs(vq, reqs, msgs, nr);
    >> +
    >> +err_unlock_free:
    >> + mutex_unlock(&vi->lock);
    >> + kfree(reqs);
    >> + return ret;
    >> +}

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      Last update: 2021-03-19 08:53    [W:3.841 / U:0.012 seconds]
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