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Subject[PATCH v5] i2c: virtio: add a virtio i2c frontend driver
Date
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.

The device specification can be found on
https://lists.oasis-open.org/archives/virtio-comment/202101/msg00008.html.

By following the specification, people may implement different
backend drivers to emulate different controllers according to
their needs.

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>
---
drivers/i2c/busses/Kconfig | 11 ++
drivers/i2c/busses/Makefile | 3 +
drivers/i2c/busses/i2c-virtio.c | 281 ++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/virtio_i2c.h | 56 ++++++++
include/uapi/linux/virtio_ids.h | 1 +
5 files changed, 352 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 05ebf75..0860395 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 615f35e..b88da08 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..8c8bc95
--- /dev/null
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -0,0 +1,281 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtio I2C Bus Driver
+ *
+ * Copyright (c) 2021 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 - 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_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;
+ u8 *buf;
+
+ for (i = 0; i < nr; i++) {
+ if (!msgs[i].len)
+ break;
+
+ reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
+
+ if (i != nr - 1)
+ reqs[i].out_hdr.flags |= 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;
+
+ buf = kzalloc(msgs[i].len, GFP_KERNEL);
+ if (!buf)
+ break;
+
+ if (msgs[i].flags & I2C_M_RD) {
+ reqs[i].read_buf = buf;
+ sg_init_one(&msg_buf, reqs[i].read_buf, msgs[i].len);
+ sgs[outcnt + incnt++] = &msg_buf;
+ } else {
+ reqs[i].write_buf = buf;
+ memcpy(reqs[i].write_buf, msgs[i].buf, msgs[i].len);
+ sg_init_one(&msg_buf, reqs[i].write_buf, msgs[i].len);
+ 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);
+ if (msgs[i].flags & I2C_M_RD) {
+ kfree(reqs[i].read_buf);
+ reqs[i].read_buf = NULL;
+ } else {
+ kfree(reqs[i].write_buf);
+ reqs[i].write_buf = NULL;
+ }
+ 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;
+
+ for (i = 0; i < nr; i++) {
+ req = (struct virtio_i2c_req *)virtqueue_get_buf(vq, &len);
+ if (!(req && req == &reqs[i])) {
+ pr_err("msg[%d]: addr=0x%x virtqueue error.\n", i, msgs[i].addr);
+ break;
+ }
+
+ if (req->in_hdr.status != VIRTIO_I2C_MSG_OK) {
+ pr_err("msg[%d]: addr=0x%x backend error.\n", i, msgs[i].addr);
+ break;
+ }
+
+ if (msgs[i].flags & I2C_M_RD) {
+ memcpy(msgs[i].buf, req->read_buf, msgs[i].len);
+ kfree(req->read_buf);
+ req->read_buf = NULL;
+ } else {
+ kfree(req->write_buf);
+ req->write_buf = NULL;
+ }
+ }
+
+ 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->i2c_lock);
+
+ ret = virtio_i2c_send_reqs(vq, reqs, msgs, num);
+ if (ret == 0)
+ goto err_unlock_free;
+ else
+ nr = ret;
+
+ virtqueue_kick(vq);
+
+ time_left = wait_for_completion_timeout(&vi->completion, adap->timeout);
+ if (!time_left) {
+ dev_err(&adap->dev, "virtio i2c backend timeout.\n");
+ ret = -ETIMEDOUT;
+ goto err_unlock_free;
+ }
+
+ ret = virtio_i2c_complete_reqs(vq, reqs, msgs, nr);
+
+ reinit_completion(&vi->completion);
+
+err_unlock_free:
+ mutex_unlock(&vi->i2c_lock);
+ kfree(reqs);
+ 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, "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 controlled 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..92febf0
--- /dev/null
+++ b/include/uapi/linux/virtio_i2c.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later WITH Linux-syscall-note */
+/*
+ * Definitions for virtio I2C Adpter
+ *
+ * Copyright (c) 2021 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_out_hdr - the virtio I2C message OUT header
+ * @addr: the controlled device address
+ * @padding: used to pad to full dword
+ * @flags: used for feature extensibility
+ */
+struct virtio_i2c_out_hdr {
+ __le16 addr;
+ __le16 padding;
+ __le32 flags;
+};
+
+/* The bit 0 of the @virtio_i2c_out_hdr.@flags, used to group the requests */
+#define VIRTIO_I2C_FLAGS_FAIL_NEXT 0x00000001
+
+/**
+ * struct virtio_i2c_in_hdr - the virtio I2C message IN header
+ * @status: the processing result from the backend
+ */
+struct virtio_i2c_in_hdr {
+ u8 status;
+};
+
+/* The final status written by the device */
+#define VIRTIO_I2C_MSG_OK 0
+#define VIRTIO_I2C_MSG_ERR 1
+
+/**
+ * struct virtio_i2c_req - the virtio I2C request structure
+ * @out_hdr: the OUT header of the virtio I2C message
+ * @write_buf: contains one I2C segment being written to the device
+ * @read_buf: contains one I2C segment being read from the device
+ * @in_hdr: the IN header of the virtio I2C message
+ */
+struct virtio_i2c_req {
+ struct virtio_i2c_out_hdr out_hdr;
+ u8 *write_buf;
+ u8 *read_buf;
+ struct virtio_i2c_in_hdr in_hdr;
+};
+
+#endif /* _UAPI_LINUX_VIRTIO_I2C_H */
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index bc1c062..6ae32db 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -54,5 +54,6 @@
#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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