drivers/i2c/busses/i2c-virtio.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Virtio I2C Bus Driver
  *
  * The Virtio I2C Specification:
  * https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
  *
  * 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/kernel.h>
 #include <linux/module.h>
 #include <linux/virtio.h>
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.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
  * @vq: the virtio virtqueue for communication
  */
 struct virtio_i2c {
 	struct virtio_device *vdev;
 	struct completion completion;
 	struct i2c_adapter adap;
 	struct virtqueue *vq;
 };

 /**
  * struct virtio_i2c_req - the virtio I2C request structure
  * @out_hdr: the OUT header of the virtio I2C message
  * @buf: the buffer into which data is read, or from which it's written
  * @in_hdr: the IN header of the virtio I2C message
  */
 struct virtio_i2c_req {
 	struct virtio_i2c_out_hdr out_hdr	____cacheline_aligned;
 	uint8_t *buf				____cacheline_aligned;
 	struct virtio_i2c_in_hdr in_hdr		____cacheline_aligned;
 };

 static void virtio_i2c_msg_done(struct virtqueue *vq)
 {
 	struct virtio_i2c *vi = vq->vdev->priv;

 	complete(&vi->completion);
 }

 static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
 				   struct virtio_i2c_req *reqs,
 				   struct i2c_msg *msgs, int num)
 {
 	struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
 	int i;

 	for (i = 0; i < num; i++) {
 		int outcnt = 0, incnt = 0;

 		/*
 		 * Only 7-bit mode supported for this moment. For the address
 		 * format, Please check the Virtio I2C Specification.
 		 */
 		reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);

 		if (msgs[i].flags & I2C_M_RD)
 			reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD);

 		if (i != num - 1)
 			reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);

 		sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
 		sgs[outcnt++] = &out_hdr;

 		if (msgs[i].len) {
 			reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
 			if (!reqs[i].buf)
 				break;

 			sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);

 			if (msgs[i].flags & I2C_M_RD)
 				sgs[outcnt + incnt++] = &msg_buf;
 			else
 				sgs[outcnt++] = &msg_buf;
 		}

 		sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
 		sgs[outcnt + incnt++] = &in_hdr;

 		if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
 			i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
 			break;
 		}
 	}

 	return i;
 }

 static int virtio_i2c_complete_reqs(struct virtqueue *vq,
 				    struct virtio_i2c_req *reqs,
 				    struct i2c_msg *msgs, int num,
 				    bool timedout)
 {
 	struct virtio_i2c_req *req;
 	bool failed = timedout;
 	unsigned int len;
 	int i, j = 0;

 	for (i = 0; i < num; i++) {
 		/* Detach the ith request from the vq */
 		req = virtqueue_get_buf(vq, &len);

 		/*
 		 * Condition req == &reqs[i] should always meet since we have
 		 * total num requests in the vq. reqs[i] can never be NULL here.
 		 */
 		if (!failed && (WARN_ON(req != &reqs[i]) ||
 				req->in_hdr.status != VIRTIO_I2C_MSG_OK))
 			failed = true;

 		i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);

 		if (!failed)
 			j++;
 	}

 	return timedout ? -ETIMEDOUT : j;
 }

 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 count;

 	reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
 	if (!reqs)
 		return -ENOMEM;

 	count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
 	if (!count)
 		goto err_free;

 	/*
 	 * For the case where count < num, i.e. we weren't able to queue all the
 	 * msgs, ideally we should abort right away and return early, but some
 	 * of the messages are already sent to the remote I2C controller and the
 	 * virtqueue will be left in undefined state in that case. We kick the
 	 * remote here to clear the virtqueue, so we can try another set of
 	 * messages later on.
 	 */

 	reinit_completion(&vi->completion);
 	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");

 	count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left);

 err_free:
 	kfree(reqs);
 	return count;
 }

 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 int virtio_i2c_probe(struct virtio_device *vdev)
 {
 	struct virtio_i2c *vi;
 	int ret;

 	if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
 		dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
 		return -EINVAL;
 	}

 	vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
 	if (!vi)
 		return -ENOMEM;

 	vdev->priv = vi;
 	vi->vdev = vdev;

 	init_completion(&vi->completion);

 	ret = virtio_i2c_setup_vqs(vi);
 	if (ret)
 		return ret;

 	vi->adap.owner = THIS_MODULE;
 	snprintf(vi->adap.name, sizeof(vi->adap.name),
 		 "i2c_virtio at virtio bus %d", vdev->index);
 	vi->adap.algo = &virtio_algorithm;
 	vi->adap.dev.parent = &vdev->dev;
 	vi->adap.dev.of_node = vdev->dev.of_node;
 	i2c_set_adapdata(&vi->adap, vi);

 	/*
 	 * Setup ACPI node for controlled devices which will be probed through
 	 * ACPI.
 	 */
 	ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));

 	ret = i2c_add_adapter(&vi->adap);
 	if (ret)
 		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_ADAPTER, VIRTIO_DEV_ANY_ID },
 	{}
 };
 MODULE_DEVICE_TABLE(virtio, id_table);

 #ifdef CONFIG_PM_SLEEP
 static int virtio_i2c_freeze(struct virtio_device *vdev)
 {
 	virtio_i2c_del_vqs(vdev);
 	return 0;
 }

 static int virtio_i2c_restore(struct virtio_device *vdev)
 {
 	return virtio_i2c_setup_vqs(vdev->priv);
 }
 #endif

 static const unsigned int features[] = {
 	VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
 };

 static struct virtio_driver virtio_i2c_driver = {
 	.feature_table		= features,
 	.feature_table_size	= ARRAY_SIZE(features),
 	.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_AUTHOR("Jie Deng <jie.deng@intel.com>");
 MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
 MODULE_DESCRIPTION("Virtio i2c bus driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Virtio I2C Bus Driver
	*
	* The Virtio I2C Specification:
	* https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
	*
	* 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/kernel.h>
	#include <linux/module.h>
	#include <linux/virtio.h>
	#include <linux/virtio_ids.h>
	#include <linux/virtio_config.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
	* @vq: the virtio virtqueue for communication
	*/
	struct virtio_i2c {
	struct virtio_device *vdev;
	struct completion completion;
	struct i2c_adapter adap;
	struct virtqueue *vq;
	};

	/**
	* struct virtio_i2c_req - the virtio I2C request structure
	* @out_hdr: the OUT header of the virtio I2C message
	* @buf: the buffer into which data is read, or from which it's written
	* @in_hdr: the IN header of the virtio I2C message
	*/
	struct virtio_i2c_req {
	struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned;
	uint8_t *buf ____cacheline_aligned;
	struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned;
	};

	static void virtio_i2c_msg_done(struct virtqueue *vq)
	{
	struct virtio_i2c *vi = vq->vdev->priv;

	complete(&vi->completion);
	}

	static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
	struct virtio_i2c_req *reqs,
	struct i2c_msg *msgs, int num)
	{
	struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
	int i;

	for (i = 0; i < num; i++) {
	int outcnt = 0, incnt = 0;

	/*
	* Only 7-bit mode supported for this moment. For the address
	* format, Please check the Virtio I2C Specification.
	*/
	reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);

	if (msgs[i].flags & I2C_M_RD)
	reqs[i].out_hdr.flags \|= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD);

	if (i != num - 1)
	reqs[i].out_hdr.flags \|= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);

	sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
	sgs[outcnt++] = &out_hdr;

	if (msgs[i].len) {
	reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
	if (!reqs[i].buf)
	break;

	sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);

	if (msgs[i].flags & I2C_M_RD)
	sgs[outcnt + incnt++] = &msg_buf;
	else
	sgs[outcnt++] = &msg_buf;
	}

	sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
	sgs[outcnt + incnt++] = &in_hdr;

	if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
	i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
	break;
	}
	}

	return i;
	}

	static int virtio_i2c_complete_reqs(struct virtqueue *vq,
	struct virtio_i2c_req *reqs,
	struct i2c_msg *msgs, int num,
	bool timedout)
	{
	struct virtio_i2c_req *req;
	bool failed = timedout;
	unsigned int len;
	int i, j = 0;

	for (i = 0; i < num; i++) {
	/* Detach the ith request from the vq */
	req = virtqueue_get_buf(vq, &len);

	/*
	* Condition req == &reqs[i] should always meet since we have
	* total num requests in the vq. reqs[i] can never be NULL here.
	*/
	if (!failed && (WARN_ON(req != &reqs[i]) \|\|
	req->in_hdr.status != VIRTIO_I2C_MSG_OK))
	failed = true;

	i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);

	if (!failed)
	j++;
	}

	return timedout ? -ETIMEDOUT : j;
	}

	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 count;

	reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
	if (!reqs)
	return -ENOMEM;

	count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
	if (!count)
	goto err_free;

	/*
	* For the case where count < num, i.e. we weren't able to queue all the
	* msgs, ideally we should abort right away and return early, but some
	* of the messages are already sent to the remote I2C controller and the
	* virtqueue will be left in undefined state in that case. We kick the
	* remote here to clear the virtqueue, so we can try another set of
	* messages later on.
	*/

	reinit_completion(&vi->completion);
	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");

	count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left);

	err_free:
	kfree(reqs);
	return count;
	}

	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 int virtio_i2c_probe(struct virtio_device *vdev)
	{
	struct virtio_i2c *vi;
	int ret;

	if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
	dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
	return -EINVAL;
	}

	vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
	if (!vi)
	return -ENOMEM;

	vdev->priv = vi;
	vi->vdev = vdev;

	init_completion(&vi->completion);

	ret = virtio_i2c_setup_vqs(vi);
	if (ret)
	return ret;

	vi->adap.owner = THIS_MODULE;
	snprintf(vi->adap.name, sizeof(vi->adap.name),
	"i2c_virtio at virtio bus %d", vdev->index);
	vi->adap.algo = &virtio_algorithm;
	vi->adap.dev.parent = &vdev->dev;
	vi->adap.dev.of_node = vdev->dev.of_node;
	i2c_set_adapdata(&vi->adap, vi);

	/*
	* Setup ACPI node for controlled devices which will be probed through
	* ACPI.
	*/
	ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));

	ret = i2c_add_adapter(&vi->adap);
	if (ret)
	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_ADAPTER, VIRTIO_DEV_ANY_ID },
	{}
	};
	MODULE_DEVICE_TABLE(virtio, id_table);

	#ifdef CONFIG_PM_SLEEP
	static int virtio_i2c_freeze(struct virtio_device *vdev)
	{
	virtio_i2c_del_vqs(vdev);
	return 0;
	}

	static int virtio_i2c_restore(struct virtio_device *vdev)
	{
	return virtio_i2c_setup_vqs(vdev->priv);
	}
	#endif

	static const unsigned int features[] = {
	VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
	};

	static struct virtio_driver virtio_i2c_driver = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.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_AUTHOR("Jie Deng <jie.deng@intel.com>");
	MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
	MODULE_DESCRIPTION("Virtio i2c bus driver");
	MODULE_LICENSE("GPL");