/*
 * uio_hv_generic - generic UIO driver for VMBus
 *
 * Copyright (c) 2013-2016 Brocade Communications Systems, Inc.
 * Copyright (c) 2016, Microsoft Corporation.
 *
 *
 * This work is licensed under the terms of the GNU GPL, version 2.
 *
 * Since the driver does not declare any device ids, you must allocate
 * id and bind the device to the driver yourself.  For example:
 *
 * # echo "f8615163-df3e-46c5-913f-f2d2f965ed0e" \
 *    > /sys/bus/vmbus/drivers/uio_hv_generic
 * # echo -n vmbus-ed963694-e847-4b2a-85af-bc9cfc11d6f3 \
 *    > /sys/bus/vmbus/drivers/hv_netvsc/unbind
 * # echo -n vmbus-ed963694-e847-4b2a-85af-bc9cfc11d6f3 \
 *    > /sys/bus/vmbus/drivers/uio_hv_generic/bind
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/uio_driver.h>
#include <linux/netdevice.h>
#include <linux/if_ether.h>
#include <linux/skbuff.h>
#include <linux/hyperv.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>

#include "../hv/hyperv_vmbus.h"

#define DRIVER_VERSION	"0.02.0"
#define DRIVER_AUTHOR	"Stephen Hemminger <sthemmin at microsoft.com>"
#define DRIVER_DESC	"Generic UIO driver for VMBus devices"

/*
 * List of resources to be mapped to user space
 * can be extended up to MAX_UIO_MAPS(5) items
 */
enum hv_uio_map {
	TXRX_RING_MAP = 0,
	INT_PAGE_MAP,
	MON_PAGE_MAP,
};

#define HV_RING_SIZE	512

struct hv_uio_private_data {
	struct uio_info info;
	struct hv_device *device;
};

static int
hv_uio_mmap(struct uio_info *info, struct vm_area_struct *vma)
{
	int mi;

	if (vma->vm_pgoff >= MAX_UIO_MAPS)
		return -EINVAL;

	if (info->mem[vma->vm_pgoff].size == 0)
		return -EINVAL;

	mi = (int)vma->vm_pgoff;

	return remap_pfn_range(vma, vma->vm_start,
			info->mem[mi].addr >> PAGE_SHIFT,
			vma->vm_end - vma->vm_start, vma->vm_page_prot);
}

/*
 * This is the irqcontrol callback to be registered to uio_info.
 * It can be used to disable/enable interrupt from user space processes.
 *
 * @param info
 *  pointer to uio_info.
 * @param irq_state
 *  state value. 1 to enable interrupt, 0 to disable interrupt.
 */
static int
hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
{
	struct hv_uio_private_data *pdata = info->priv;
	struct hv_device *dev = pdata->device;

	dev->channel->inbound.ring_buffer->interrupt_mask = !irq_state;
	virt_mb();

	return 0;
}

/*
 * Callback from vmbus_event when something is in inbound ring.
 */
static void hv_uio_channel_cb(void *context)
{
	struct hv_uio_private_data *pdata = context;
	struct hv_device *dev = pdata->device;

	dev->channel->inbound.ring_buffer->interrupt_mask = 1;
	virt_mb();

	uio_event_notify(&pdata->info);
}

static int
hv_uio_probe(struct hv_device *dev,
	     const struct hv_vmbus_device_id *dev_id)
{
	struct hv_uio_private_data *pdata;
	int ret;

	pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
	if (!pdata)
		return -ENOMEM;

	ret = vmbus_open(dev->channel, HV_RING_SIZE * PAGE_SIZE,
			 HV_RING_SIZE * PAGE_SIZE, NULL, 0,
			 hv_uio_channel_cb, pdata);
	if (ret)
		goto fail;

	/* Communicating with host has to be via shared memory not hypercall */
	if (!dev->channel->offermsg.monitor_allocated) {
		dev_err(&dev->device, "vmbus channel requires hypercall\n");
		ret = -ENOTSUPP;
		goto fail_close;
	}

	dev->channel->inbound.ring_buffer->interrupt_mask = 1;
	set_channel_read_mode(dev->channel, HV_CALL_DIRECT);

	/* Fill general uio info */
	pdata->info.name = "uio_hv_generic";
	pdata->info.version = DRIVER_VERSION;
	pdata->info.irqcontrol = hv_uio_irqcontrol;
	pdata->info.mmap = hv_uio_mmap;
	pdata->info.irq = UIO_IRQ_CUSTOM;

	/* mem resources */
	pdata->info.mem[TXRX_RING_MAP].name = "txrx_rings";
	pdata->info.mem[TXRX_RING_MAP].addr
		= virt_to_phys(dev->channel->ringbuffer_pages);
	pdata->info.mem[TXRX_RING_MAP].size
		= dev->channel->ringbuffer_pagecount * PAGE_SIZE;
	pdata->info.mem[TXRX_RING_MAP].memtype = UIO_MEM_LOGICAL;

	pdata->info.mem[INT_PAGE_MAP].name = "int_page";
	pdata->info.mem[INT_PAGE_MAP].addr =
		virt_to_phys(vmbus_connection.int_page);
	pdata->info.mem[INT_PAGE_MAP].size = PAGE_SIZE;
	pdata->info.mem[INT_PAGE_MAP].memtype = UIO_MEM_LOGICAL;

	pdata->info.mem[MON_PAGE_MAP].name = "monitor_pages";
	pdata->info.mem[MON_PAGE_MAP].addr =
		virt_to_phys(vmbus_connection.monitor_pages[1]);
	pdata->info.mem[MON_PAGE_MAP].size = PAGE_SIZE;
	pdata->info.mem[MON_PAGE_MAP].memtype = UIO_MEM_LOGICAL;

	pdata->info.priv = pdata;
	pdata->device = dev;

	ret = uio_register_device(&dev->device, &pdata->info);
	if (ret) {
		dev_err(&dev->device, "hv_uio register failed\n");
		goto fail_close;
	}

	hv_set_drvdata(dev, pdata);

	return 0;

fail_close:
	vmbus_close(dev->channel);
fail:
	kfree(pdata);

	return ret;
}

static int
hv_uio_remove(struct hv_device *dev)
{
	struct hv_uio_private_data *pdata = hv_get_drvdata(dev);

	if (!pdata)
		return 0;

	uio_unregister_device(&pdata->info);
	hv_set_drvdata(dev, NULL);
	vmbus_close(dev->channel);
	kfree(pdata);
	return 0;
}

static struct hv_driver hv_uio_drv = {
	.name = "uio_hv_generic",
	.id_table = NULL, /* only dynamic id's */
	.probe = hv_uio_probe,
	.remove = hv_uio_remove,
};

static int __init
hyperv_module_init(void)
{
	return vmbus_driver_register(&hv_uio_drv);
}

static void __exit
hyperv_module_exit(void)
{
	vmbus_driver_unregister(&hv_uio_drv);
}

module_init(hyperv_module_init);
module_exit(hyperv_module_exit);

MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);