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    SubjectRe: [PATCH] i2c: virtio: add a virtio i2c frontend driver
    On Thu, Sep 03, 2020 at 01:34:45PM +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.
    >
    > 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.

    Please reserve the ID with the virtio tc so no one conflicts.


    > 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>
    > ---
    > drivers/i2c/busses/Kconfig | 11 ++
    > drivers/i2c/busses/Makefile | 3 +
    > drivers/i2c/busses/i2c-virtio.c | 276 ++++++++++++++++++++++++++++++++++++++++
    > include/uapi/linux/virtio_ids.h | 1 +
    > 4 files changed, 291 insertions(+)
    > create mode 100644 drivers/i2c/busses/i2c-virtio.c
    >
    > 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
    > + 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..47f9fd1
    > --- /dev/null
    > +++ b/drivers/i2c/busses/i2c-virtio.c
    > @@ -0,0 +1,276 @@
    > +// 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_ids.h>
    > +#include <linux/virtio_config.h>
    > +
    > +#define VIRTIO_I2C_MSG_OK 0
    > +#define VIRTIO_I2C_MSG_ERR 1
    > +
    > +/**
    > + * 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 {
    > + __virtio16 addr;
    > + __virtio16 flags;
    > + __virtio16 len;
    > +} __packed;

    virtio16 is for legacy devices, modern ones should be __le.
    and we don't really need to pack it I think.

    > +
    > +/**
    > + * 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;
    > + char *buf;
    > + u8 status;
    > +};
    > +
    > +/**
    > + * 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;
    > +
    > + 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;
    > +
    > + 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;
    > + }
    > + if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
    > + dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
    > + i, vmsg_i->hdr.addr, vmsg_i->status);
    > + ret = i;
    > + goto err_unlock_free;
    > + }
    > + if ((vmsg_i->hdr.flags & I2C_M_RD) && vmsg_i->hdr.len)
    > + memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
    > +
    > + kfree(vmsg_i->buf);
    > + vmsg_i->buf = NULL;
    > + }
    > + reinit_completion(&vi->completion);
    > + }
    > + if (i == num)
    > + ret = num;
    > +
    > +err_unlock_free:
    > + mutex_unlock(&vi->i2c_lock);
    > + kfree(vmsg_o->buf);
    > + kfree(vmsg_o);
    > + return ret;
    > +}
    > +
    > +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, "i2c-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) {
    > + dev_err(&vdev->dev, "failed to add virtio-i2c adapter.\n");
    > + virtio_i2c_del_vqs(vdev);
    > + }
    > +
    > + 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_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 */
    > --
    > 2.7.4

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      Last update: 2020-09-03 11:59    [W:4.419 / U:0.348 seconds]
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