Messages in this thread | | | Subject | Re: [PATCH] i2c: virtio: add a virtio i2c frontend driver | From | Jason Wang <> | Date | Mon, 7 Sep 2020 13:40:20 +0800 |
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On 2020/9/4 下午9:21, Jie Deng wrote: > > On 2020/9/4 12:06, Jason Wang wrote: >> >>> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig >>> index 293e7a0..70c8e30 100644 >>> --- a/drivers/i2c/busses/Kconfig >>> +++ b/drivers/i2c/busses/Kconfig >>> @@ -21,6 +21,17 @@ config I2C_ALI1535 >>> This driver can also be built as a module. If so, the module >>> will be called i2c-ali1535. >>> +config I2C_VIRTIO >>> + tristate "Virtio I2C Adapter" >>> + depends on VIRTIO >> >> >> I guess it should depend on some I2C module here. >> > The dependency of I2C is included in the Kconfig in its parent directory. > So there is nothing special to add here.
Ok.
> > >> >>> >>> +struct virtio_i2c_msg { >>> + struct virtio_i2c_hdr hdr; >>> + char *buf; >>> + u8 status; >> >> >> Any reason for separating status out of virtio_i2c_hdr? >> > The status is not from i2c_msg.
You meant ic2_hdr? You embed status in virtio_i2c_msg anyway.
> So I put it out of virtio_i2c_hdr.
Something like status or response is pretty common in virtio request (e.g net or scsi), if no special reason, it's better to keep it in the hdr.
> >> >>> +}; >>> + >>> +/** >>> + * struct virtio_i2c - virtio I2C data >>> + * @vdev: virtio device for this controller >>> + * @completion: completion of virtio I2C message >>> + * @adap: I2C adapter for this controller >>> + * @i2c_lock: lock for virtqueue processing >>> + * @vq: the virtio virtqueue for communication >>> + */ >>> +struct virtio_i2c { >>> + struct virtio_device *vdev; >>> + struct completion completion; >>> + struct i2c_adapter adap; >>> + struct mutex i2c_lock; >>> + struct virtqueue *vq; >>> +}; >>> + >>> +static void virtio_i2c_msg_done(struct virtqueue *vq) >>> +{ >>> + struct virtio_i2c *vi = vq->vdev->priv; >>> + >>> + complete(&vi->completion); >>> +} >>> + >>> +static int virtio_i2c_add_msg(struct virtqueue *vq, >>> + struct virtio_i2c_msg *vmsg, >>> + struct i2c_msg *msg) >>> +{ >>> + struct scatterlist *sgs[3], hdr, bout, bin, status; >>> + int outcnt = 0, incnt = 0; >>> + >>> + if (!msg->len) >>> + return -EINVAL; >>> + >>> + vmsg->hdr.addr = msg->addr; >>> + vmsg->hdr.flags = msg->flags; >>> + vmsg->hdr.len = msg->len; >> >> >> Missing endian conversion? >> > You are right. Need conversion here. >> >>> + >>> + vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL); >>> + if (!vmsg->buf) >>> + return -ENOMEM; >>> + >>> + sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr)); >>> + sgs[outcnt++] = &hdr; >>> + if (vmsg->hdr.flags & I2C_M_RD) { >>> + sg_init_one(&bin, vmsg->buf, msg->len); >>> + sgs[outcnt + incnt++] = &bin; >>> + } else { >>> + memcpy(vmsg->buf, msg->buf, msg->len); >>> + sg_init_one(&bout, vmsg->buf, msg->len); >>> + sgs[outcnt++] = &bout; >>> + } >>> + sg_init_one(&status, &vmsg->status, sizeof(vmsg->status)); >>> + sgs[outcnt + incnt++] = &status; >>> + >>> + return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg, >>> GFP_KERNEL); >>> +} >>> + >>> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg >>> *msgs, int num) >>> +{ >>> + struct virtio_i2c *vi = i2c_get_adapdata(adap); >>> + struct virtio_i2c_msg *vmsg_o, *vmsg_i; >>> + struct virtqueue *vq = vi->vq; >>> + unsigned long time_left; >>> + int len, i, ret = 0; >>> + >>> + vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL); >>> + if (!vmsg_o) >>> + return -ENOMEM; >> >> >> It looks to me we can avoid the allocation by embedding >> virtio_i2c_msg into struct virtio_i2c; >> > Yeah... That's better. Thanks. > > >> >>> + >>> + mutex_lock(&vi->i2c_lock); >>> + vmsg_o->buf = NULL; >>> + for (i = 0; i < num; i++) { >>> + ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]); >>> + if (ret) { >>> + dev_err(&adap->dev, "failed to add msg[%d] to >>> virtqueue.\n", i); >>> + goto err_unlock_free; >>> + } >>> + >>> + virtqueue_kick(vq); >>> + >>> + time_left = wait_for_completion_timeout(&vi->completion, >>> adap->timeout); >>> + if (!time_left) { >>> + dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n", i, >>> msgs[i].addr); >>> + ret = i; >>> + goto err_unlock_free; >>> + } >>> + >>> + vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len); >>> + if (vmsg_i) { >>> + /* vmsg_i should point to the same address with vmsg_o */ >>> + if (vmsg_i != vmsg_o) { >>> + dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue >>> error.\n", >>> + i, vmsg_i->hdr.addr); >>> + ret = i; >>> + goto err_unlock_free; >>> + } >> >> >> Does this imply in order completion of i2c device? (E.g what happens >> if multiple virtio i2c requests are submitted) >> >> Btw, this always use a single descriptor once a time which makes me >> suspect if a virtqueue(virtio) is really needed. It looks to me we >> can utilize the virtqueue by submit the request in a batch. >> > I'm afraid not all physical devices support batch.
Yes but I think I meant for the virtio device not the physical one. It's impossible to forbid batching if you have a queue anyway ...
> I'd like to keep the current design and consider > your suggestion as a possible optimization in the future. > > Thanks. > > >>> >>> +} >>> + >>> +static void virtio_i2c_del_vqs(struct virtio_device *vdev) >>> +{ >>> + vdev->config->reset(vdev); >> >> >> Why need reset here? >> >> Thanks >> > I'm following what other virtio drivers do. > They reset the devices before they clean up the queues.
You're ring.
Thanks
> > >> >>> + vdev->config->del_vqs(vdev); >>> +} >>> + >>> +static int virtio_i2c_setup_vqs(struct virtio_i2c *vi) >>> +{ >>> + struct virtio_device *vdev = vi->vdev; >>> + >>> + vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, >>> "i2c-msg"); >> >> >> We've in the scope of ic2, so "msg" should be sufficient. >> >> > OK. Will change this name. Thanks. > > >>> + return PTR_ERR_OR_ZERO(vi->vq); >
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