Re: [PATCH] i2c: virtio: add a virtio i2c frontend driver

Jason Wang <jasowang@xxxxxxxxxx> · Thu, 3 Sep 2020 14:12:45 +0800

On 2020/9/3 下午1:34, 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.


May I know the reason why don't you use i2c or virtio directly?



The virtio device ID 34 is used for this I2C adpter since IDs
before 34 have been reserved by other virtio devices.


Is there a link to the spec patch?

Thanks



Co-developed-by: Conghui Chen <conghui.chen@xxxxxxxxx>
Signed-off-by: Conghui Chen <conghui.chen@xxxxxxxxx>
Signed-off-by: Jie Deng <jie.deng@xxxxxxxxx>
Reviewed-by: Shuo Liu <shuo.a.liu@xxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
  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;
+
+/**
+ * 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 */







