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SubjectRe: [PATCH v3] i2c: virtio: add a virtio i2c frontend driver
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On 2020/9/22 上午10:58, 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.
>
> This driver communicates with the backend driver through a
> virtio I2C message structure which includes following parts:
>
> - Header: i2c_msg addr, flags, len.
> - Data buffer: the pointer to the I2C msg data.
> - Status: the processing result from the backend.
>
> People may implement different backend drivers to emulate
> different controllers according to their needs. A backend
> example can be found in the device model of the open source
> project ACRN. For more information, please refer to
> https://projectacrn.org.
>
> The virtio device ID 34 is used for this I2C adpter since IDs
> before 34 have been reserved by other virtio devices.
>
> Co-developed-by: Conghui Chen <conghui.chen@intel.com>
> Signed-off-by: Conghui Chen <conghui.chen@intel.com>
> Signed-off-by: Jie Deng <jie.deng@intel.com>
> Reviewed-by: Shuo Liu <shuo.a.liu@intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> The device ID request:
> https://github.com/oasis-tcs/virtio-spec/issues/85
>
> The specification:
> https://lists.oasis-open.org/archives/virtio-comment/202009/msg00021.html
>
> Changes in v3:
> - Move the interface into uAPI according to Jason.
> - Fix issues reported by Dan Carpenter.
> - Fix typo reported by Randy.
>
> Changes in v2:
> - Addressed comments received from Michael, Andy and Jason.
>
> drivers/i2c/busses/Kconfig | 11 ++
> drivers/i2c/busses/Makefile | 3 +
> drivers/i2c/busses/i2c-virtio.c | 256 ++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/virtio_i2c.h | 31 +++++
> include/uapi/linux/virtio_ids.h | 1 +
> 5 files changed, 302 insertions(+)
> create mode 100644 drivers/i2c/busses/i2c-virtio.c
> create mode 100644 include/uapi/linux/virtio_i2c.h
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 293e7a0..f2f6543 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
> + help
> + If you say yes to this option, support will be included for the virtio
> + I2C adapter driver. The hardware can be emulated by any device model
> + software according to the virtio protocol.
> +
> + This driver can also be built as a module. If so, the module
> + will be called i2c-virtio.
> +
> config I2C_ALI1563
> tristate "ALI 1563"
> depends on PCI
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 19aff0e..821acfa 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -6,6 +6,9 @@
> # ACPI drivers
> obj-$(CONFIG_I2C_SCMI) += i2c-scmi.o
>
> +# VIRTIO I2C host controller driver
> +obj-$(CONFIG_I2C_VIRTIO) += i2c-virtio.o
> +
> # PC SMBus host controller drivers
> obj-$(CONFIG_I2C_ALI1535) += i2c-ali1535.o
> obj-$(CONFIG_I2C_ALI1563) += i2c-ali1563.o
> diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
> new file mode 100644
> index 0000000..48fd780
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-virtio.c
> @@ -0,0 +1,256 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Virtio I2C Bus Driver
> + *
> + * Copyright (c) 2020 Intel Corporation. All rights reserved.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/io.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/wait.h>
> +
> +#include <linux/virtio.h>
> +#include <linux/virtio_i2c.h>
> +
> +/**
> + * struct virtio_i2c_msg - the virtio I2C message structure
> + * @hdr: the virtio I2C message header
> + * @buf: virtio I2C message data buffer
> + * @status: the processing result from the backend
> + */
> +struct virtio_i2c_msg {
> + struct virtio_i2c_hdr hdr;
> + u8 *buf;
> + u8 status;
> +};
> +
> +/**
> + * struct virtio_i2c - virtio I2C data
> + * @vdev: virtio device for this controller
> + * @completion: completion of virtio I2C message
> + * @vmsg: the virtio I2C message for communication
> + * @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 virtio_i2c_msg vmsg;
> + 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 = cpu_to_le16(msg->addr);
> + vmsg->hdr.flags = cpu_to_le16(msg->flags);
> + vmsg->hdr.len = cpu_to_le16(msg->len);
> +
> + vmsg->buf = kzalloc(msg->len, GFP_KERNEL);
> + if (!vmsg->buf)
> + return -ENOMEM;
> +
> + sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr));
> + sgs[outcnt++] = &hdr;
> + if (msg->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 virtqueue *vq = vi->vq;
> + struct virtio_i2c_msg *vmsg;
> + unsigned long time_left;
> + int len, i, ret = 0;
> +
> + mutex_lock(&vi->i2c_lock);
> + vmsg = &vi->vmsg;
> + vmsg->buf = NULL;
> +
> + for (i = 0; i < num; i++) {
> + ret = virtio_i2c_add_msg(vq, vmsg, &msgs[i]);
> + if (ret) {
> + dev_err(&adap->dev, "failed to add msg[%d] to virtqueue.\n", i);
> + break;
> + }
> +
> + 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);
> + break;
> + }


You don't set error number here. Is this intended?

And using a timeout here is not good, and if the request is finished
just after the timeout, in the next xfer you may hit the following check.

It's better to use either interrupt here.


> +
> + vmsg = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
> + /* vmsg should point to the same address with &vi->vmsg */
> + if ((!vmsg) || (vmsg != &vi->vmsg)) {
> + dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue error.\n",
> + i, msgs[i].addr);
> + break;
> + }


So I think we can remove this check. Consider only one descriptor will
be used at most, unless there's a bug in the device (and no other driver
to the similar check), we should not hit this.

Btw, as I replied in the previous version, the device should be cacpable
of dealing of a batch of requests through the virtqueue, otherwise it's
meaningless to use a queue here.


> +
> + if (vmsg->status != VIRTIO_I2C_MSG_OK) {
> + dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
> + i, msgs[i].addr, vmsg->status);
> + break;
> + }
> +
> + if ((msgs[i].flags & I2C_M_RD) && msgs[i].len)
> + memcpy(msgs[i].buf, vmsg->buf, msgs[i].len);
> +
> + kfree(vmsg->buf);
> + vmsg->buf = NULL;
> +
> + reinit_completion(&vi->completion);
> + }
> +
> + mutex_unlock(&vi->i2c_lock);
> + kfree(vi->vmsg.buf);
> + vi->vmsg.buf = NULL;
> + return ((ret < 0) ? ret : i);
> +}
> +
> +static void virtio_i2c_del_vqs(struct virtio_device *vdev)
> +{
> + vdev->config->reset(vdev);
> + 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, "msg");
> + return PTR_ERR_OR_ZERO(vi->vq);
> +}
> +
> +static u32 virtio_i2c_func(struct i2c_adapter *adap)
> +{
> + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm virtio_algorithm = {
> + .master_xfer = virtio_i2c_xfer,
> + .functionality = virtio_i2c_func,
> +};
> +
> +static struct i2c_adapter virtio_adapter = {
> + .owner = THIS_MODULE,
> + .name = "Virtio I2C Adapter",
> + .class = I2C_CLASS_DEPRECATED,
> + .algo = &virtio_algorithm,
> +};
> +
> +static int virtio_i2c_probe(struct virtio_device *vdev)
> +{
> + struct device *pdev = vdev->dev.parent;
> + struct virtio_i2c *vi;
> + int ret;
> +
> + vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
> + if (!vi)
> + return -ENOMEM;
> +
> + vdev->priv = vi;
> + vi->vdev = vdev;
> +
> + mutex_init(&vi->i2c_lock);
> + init_completion(&vi->completion);
> +
> + ret = virtio_i2c_setup_vqs(vi);
> + if (ret)
> + return ret;
> +
> + vi->adap = virtio_adapter;
> + i2c_set_adapdata(&vi->adap, vi);
> + vi->adap.dev.parent = &vdev->dev;
> + /* Setup ACPI node for slave devices which will be probed through ACPI */
> + ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(pdev));
> + vi->adap.timeout = HZ / 10;
> +
> + ret = i2c_add_adapter(&vi->adap);
> + if (ret) {
> + virtio_i2c_del_vqs(vdev);
> + dev_err(&vdev->dev, "failed to add virtio-i2c adapter.\n");
> + }
> +
> + return ret;
> +}
> +
> +static void virtio_i2c_remove(struct virtio_device *vdev)
> +{
> + struct virtio_i2c *vi = vdev->priv;
> +
> + i2c_del_adapter(&vi->adap);
> + virtio_i2c_del_vqs(vdev);
> +}
> +
> +static struct virtio_device_id id_table[] = {
> + { VIRTIO_ID_I2C_ADPTER, VIRTIO_DEV_ANY_ID },
> + {}
> +};
> +MODULE_DEVICE_TABLE(virtio, id_table);
> +
> +static int __maybe_unused virtio_i2c_freeze(struct virtio_device *vdev)
> +{
> + virtio_i2c_del_vqs(vdev);
> + return 0;
> +}
> +
> +static int __maybe_unused virtio_i2c_restore(struct virtio_device *vdev)
> +{
> + return virtio_i2c_setup_vqs(vdev->priv);
> +}
> +
> +static struct virtio_driver virtio_i2c_driver = {
> + .id_table = id_table,
> + .probe = virtio_i2c_probe,
> + .remove = virtio_i2c_remove,
> + .driver = {
> + .name = "i2c_virtio",
> + },
> +#ifdef CONFIG_PM_SLEEP
> + .freeze = virtio_i2c_freeze,
> + .restore = virtio_i2c_restore,
> +#endif
> +};
> +module_virtio_driver(virtio_i2c_driver);
> +
> +MODULE_DESCRIPTION("Virtio i2c bus driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/virtio_i2c.h b/include/uapi/linux/virtio_i2c.h
> new file mode 100644
> index 0000000..7413e45
> --- /dev/null
> +++ b/include/uapi/linux/virtio_i2c.h
> @@ -0,0 +1,31 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause */
> +/*
> + * Definitions for virtio I2C Adpter
> + *
> + * Copyright (c) 2020 Intel Corporation. All rights reserved.
> + */
> +
> +#ifndef _UAPI_LINUX_VIRTIO_I2C_H
> +#define _UAPI_LINUX_VIRTIO_I2C_H
> +
> +#include <linux/types.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_config.h>
> +
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> + __le16 addr;
> + __le16 flags;
> + __le16 len;
> +};


I'm afraid this is not complete. E.g the status is missed.

I suspect what virtio-scsi use is better. Which split the in from the
out instead of reusing the same buffer. And it can ease the uAPI header
export.

Thanks


> +
> +/* The final status written by the device */
> +#define VIRTIO_I2C_MSG_OK 0
> +#define VIRTIO_I2C_MSG_ERR 1
> +
> +#endif /* _UAPI_LINUX_VIRTIO_I2C_H */
> diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
> index b052355..398ef2d 100644
> --- a/include/uapi/linux/virtio_ids.h
> +++ b/include/uapi/linux/virtio_ids.h
> @@ -48,5 +48,6 @@
> #define VIRTIO_ID_FS 26 /* virtio filesystem */
> #define VIRTIO_ID_PMEM 27 /* virtio pmem */
> #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
> +#define VIRTIO_ID_I2C_ADPTER 34 /* virtio i2c adpter */
>
> #endif /* _LINUX_VIRTIO_IDS_H */

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