linux/debian/patches/patchset-zen/sauce/0001-ZEN-Add-VHBA-driver.patch

From 95490afcba944883e7f911214391a1a1e2fa3261 Mon Sep 17 00:00:00 2001
From: "Jan Alexander Steffens (heftig)" <heftig@archlinux.org>
Date: Mon, 26 Apr 2021 22:12:46 +0200
Subject: ZEN: Add VHBA driver

remote https://github.com/cdemu/cdemu
tag    vhba-module-20240917
---
 drivers/scsi/Kconfig       |    2 +
 drivers/scsi/Makefile      |    1 +
 drivers/scsi/vhba/Kconfig  |    9 +
 drivers/scsi/vhba/Makefile |    4 +
 drivers/scsi/vhba/vhba.c   | 1124 ++++++++++++++++++++++++++++++++++++
 5 files changed, 1140 insertions(+)
 create mode 100644 drivers/scsi/vhba/Kconfig
 create mode 100644 drivers/scsi/vhba/Makefile
 create mode 100644 drivers/scsi/vhba/vhba.c

--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -1522,4 +1522,6 @@ endif # SCSI_LOWLEVEL
 
 source "drivers/scsi/device_handler/Kconfig"
 
+source "drivers/scsi/vhba/Kconfig"
+
 endmenu
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -153,6 +153,7 @@ obj-$(CONFIG_CHR_DEV_SCH)	+= ch.o
 obj-$(CONFIG_SCSI_ENCLOSURE)	+= ses.o
 
 obj-$(CONFIG_SCSI_HISI_SAS) += hisi_sas/
+obj-$(CONFIG_VHBA)		+= vhba/
 
 # This goes last, so that "real" scsi devices probe earlier
 obj-$(CONFIG_SCSI_DEBUG)	+= scsi_debug.o
--- /dev/null
+++ b/drivers/scsi/vhba/Kconfig
@@ -0,0 +1,9 @@
+config VHBA
+	tristate "Virtual (SCSI) Host Bus Adapter"
+	depends on SCSI
+	help
+	  This is the in-kernel part of CDEmu, a CD/DVD-ROM device
+	  emulator.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called vhba.
--- /dev/null
+++ b/drivers/scsi/vhba/Makefile
@@ -0,0 +1,4 @@
+VHBA_VERSION := 20240917
+
+obj-$(CONFIG_VHBA)		+= vhba.o
+ccflags-y := -DVHBA_VERSION=\"$(VHBA_VERSION)\" -Werror
--- /dev/null
+++ b/drivers/scsi/vhba/vhba.c
@@ -0,0 +1,1124 @@
+/*
+ * vhba.c
+ *
+ * Copyright (C) 2007-2012 Chia-I Wu <olvaffe AT gmail DOT com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#define pr_fmt(fmt) "vhba: " fmt
+
+#include <linux/version.h>
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/highmem.h>
+#include <linux/fs.h>
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0)
+#include <linux/sched/signal.h>
+#else
+#include <linux/sched.h>
+#endif
+#include <linux/platform_device.h>
+#include <linux/miscdevice.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/scatterlist.h>
+#ifdef CONFIG_COMPAT
+#include <linux/compat.h>
+#endif
+#include <asm/uaccess.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_tcq.h>
+
+
+MODULE_AUTHOR("Chia-I Wu");
+MODULE_VERSION(VHBA_VERSION);
+MODULE_DESCRIPTION("Virtual SCSI HBA");
+MODULE_LICENSE("GPL");
+
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 15, 0)
+#define sdev_dbg(sdev, fmt, a...) \
+    dev_dbg(&(sdev)->sdev_gendev, fmt, ##a)
+#define scmd_dbg(scmd, fmt, a...) \
+    dev_dbg(&(scmd)->device->sdev_gendev, fmt, ##a)
+#endif
+
+#define VHBA_MAX_SECTORS_PER_IO 256
+#define VHBA_MAX_BUS 16
+#define VHBA_MAX_ID 16
+#define VHBA_MAX_DEVICES (VHBA_MAX_BUS * (VHBA_MAX_ID-1))
+#define VHBA_KBUF_SIZE PAGE_SIZE
+
+#define DATA_TO_DEVICE(dir) ((dir) == DMA_TO_DEVICE || (dir) == DMA_BIDIRECTIONAL)
+#define DATA_FROM_DEVICE(dir) ((dir) == DMA_FROM_DEVICE || (dir) == DMA_BIDIRECTIONAL)
+
+
+static int vhba_can_queue = 32;
+module_param_named(can_queue, vhba_can_queue, int, 0);
+
+
+enum vhba_req_state {
+    VHBA_REQ_FREE,
+    VHBA_REQ_PENDING,
+    VHBA_REQ_READING,
+    VHBA_REQ_SENT,
+    VHBA_REQ_WRITING,
+};
+
+struct vhba_command {
+    struct scsi_cmnd *cmd;
+    /* metatags are per-host. not to be confused with
+       queue tags that are usually per-lun */
+    unsigned long metatag;
+    int status;
+    struct list_head entry;
+};
+
+struct vhba_device {
+    unsigned int num;
+    spinlock_t cmd_lock;
+    struct list_head cmd_list;
+    wait_queue_head_t cmd_wq;
+    atomic_t refcnt;
+
+    unsigned char *kbuf;
+    size_t kbuf_size;
+};
+
+struct vhba_host {
+    struct Scsi_Host *shost;
+    spinlock_t cmd_lock;
+    int cmd_next;
+    struct vhba_command *commands;
+    spinlock_t dev_lock;
+    struct vhba_device *devices[VHBA_MAX_DEVICES];
+    int num_devices;
+    DECLARE_BITMAP(chgmap, VHBA_MAX_DEVICES);
+    int chgtype[VHBA_MAX_DEVICES];
+    struct work_struct scan_devices;
+};
+
+#define MAX_COMMAND_SIZE 16
+
+struct vhba_request {
+    __u32 metatag;
+    __u32 lun;
+    __u8 cdb[MAX_COMMAND_SIZE];
+    __u8 cdb_len;
+    __u32 data_len;
+};
+
+struct vhba_response {
+    __u32 metatag;
+    __u32 status;
+    __u32 data_len;
+};
+
+
+
+static struct vhba_command *vhba_alloc_command (void);
+static void vhba_free_command (struct vhba_command *vcmd);
+
+static struct platform_device vhba_platform_device;
+
+
+
+/* These functions define a symmetric 1:1 mapping between device numbers and
+   the bus and id. We have reserved the last id per bus for the host itself. */
+static void devnum_to_bus_and_id(unsigned int devnum, unsigned int *bus, unsigned int *id)
+{
+    *bus = devnum / (VHBA_MAX_ID-1);
+    *id  = devnum % (VHBA_MAX_ID-1);
+}
+
+static unsigned int bus_and_id_to_devnum(unsigned int bus, unsigned int id)
+{
+    return (bus * (VHBA_MAX_ID-1)) + id;
+}
+
+static struct vhba_device *vhba_device_alloc (void)
+{
+    struct vhba_device *vdev;
+
+    vdev = kzalloc(sizeof(struct vhba_device), GFP_KERNEL);
+    if (!vdev) {
+        return NULL;
+    }
+
+    spin_lock_init(&vdev->cmd_lock);
+    INIT_LIST_HEAD(&vdev->cmd_list);
+    init_waitqueue_head(&vdev->cmd_wq);
+    atomic_set(&vdev->refcnt, 1);
+
+    vdev->kbuf = NULL;
+    vdev->kbuf_size = 0;
+
+    return vdev;
+}
+
+static void vhba_device_put (struct vhba_device *vdev)
+{
+    if (atomic_dec_and_test(&vdev->refcnt)) {
+        kfree(vdev);
+    }
+}
+
+static struct vhba_device *vhba_device_get (struct vhba_device *vdev)
+{
+    atomic_inc(&vdev->refcnt);
+
+    return vdev;
+}
+
+static int vhba_device_queue (struct vhba_device *vdev, struct scsi_cmnd *cmd)
+{
+    struct vhba_host *vhost;
+    struct vhba_command *vcmd;
+    unsigned long flags;
+
+    vhost = platform_get_drvdata(&vhba_platform_device);
+
+    vcmd = vhba_alloc_command();
+    if (!vcmd) {
+        return SCSI_MLQUEUE_HOST_BUSY;
+    }
+
+    vcmd->cmd = cmd;
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 15, 0)
+    vcmd->metatag = scsi_cmd_to_rq(vcmd->cmd)->tag;
+#else
+    vcmd->metatag = vcmd->cmd->request->tag;
+#endif
+    list_add_tail(&vcmd->entry, &vdev->cmd_list);
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    wake_up_interruptible(&vdev->cmd_wq);
+
+    return 0;
+}
+
+static int vhba_device_dequeue (struct vhba_device *vdev, struct scsi_cmnd *cmd)
+{
+    struct vhba_command *vcmd;
+    int retval;
+    unsigned long flags;
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+    list_for_each_entry(vcmd, &vdev->cmd_list, entry) {
+        if (vcmd->cmd == cmd) {
+            list_del_init(&vcmd->entry);
+            break;
+        }
+    }
+
+    /* command not found */
+    if (&vcmd->entry == &vdev->cmd_list) {
+        spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+        return SUCCESS;
+    }
+
+    while (vcmd->status == VHBA_REQ_READING || vcmd->status == VHBA_REQ_WRITING) {
+        spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+        scmd_dbg(cmd, "wait for I/O before aborting\n");
+        schedule_timeout(1);
+        spin_lock_irqsave(&vdev->cmd_lock, flags);
+    }
+
+    retval = (vcmd->status == VHBA_REQ_SENT) ? FAILED : SUCCESS;
+
+    vhba_free_command(vcmd);
+
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    return retval;
+}
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 19, 0)
+static int vhba_slave_alloc(struct scsi_device *sdev)
+{
+    struct Scsi_Host *shost = sdev->host;
+
+    sdev_dbg(sdev, "enabling tagging (queue depth: %i).\n", sdev->queue_depth);
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+    if (!shost_use_blk_mq(shost) && shost->bqt) {
+#else
+    if (shost->bqt) {
+#endif
+        blk_queue_init_tags(sdev->request_queue, sdev->queue_depth, shost->bqt);
+    }
+    scsi_adjust_queue_depth(sdev, 0, sdev->queue_depth);
+
+    return 0;
+}
+#endif
+
+static void vhba_scan_devices_add (struct vhba_host *vhost, int bus, int id)
+{
+    struct scsi_device *sdev;
+
+    sdev = scsi_device_lookup(vhost->shost, bus, id, 0);
+    if (!sdev) {
+        scsi_add_device(vhost->shost, bus, id, 0);
+    } else {
+        dev_warn(&vhost->shost->shost_gendev, "tried to add an already-existing device %d:%d:0!\n", bus, id);
+        scsi_device_put(sdev);
+    }
+}
+
+static void vhba_scan_devices_remove (struct vhba_host *vhost, int bus, int id)
+{
+    struct scsi_device *sdev;
+
+    sdev = scsi_device_lookup(vhost->shost, bus, id, 0);
+    if (sdev) {
+        scsi_remove_device(sdev);
+        scsi_device_put(sdev);
+    } else {
+        dev_warn(&vhost->shost->shost_gendev, "tried to remove non-existing device %d:%d:0!\n", bus, id);
+    }
+}
+
+static void vhba_scan_devices (struct work_struct *work)
+{
+    struct vhba_host *vhost = container_of(work, struct vhba_host, scan_devices);
+    unsigned long flags;
+    int change, exists;
+    unsigned int devnum;
+    unsigned int bus, id;
+
+    for (;;) {
+        spin_lock_irqsave(&vhost->dev_lock, flags);
+
+        devnum = find_first_bit(vhost->chgmap, VHBA_MAX_DEVICES);
+        if (devnum >= VHBA_MAX_DEVICES) {
+            spin_unlock_irqrestore(&vhost->dev_lock, flags);
+            break;
+        }
+        change = vhost->chgtype[devnum];
+        exists = vhost->devices[devnum] != NULL;
+
+        vhost->chgtype[devnum] = 0;
+        clear_bit(devnum, vhost->chgmap);
+
+        spin_unlock_irqrestore(&vhost->dev_lock, flags);
+
+        devnum_to_bus_and_id(devnum, &bus, &id);
+
+        if (change < 0) {
+            dev_dbg(&vhost->shost->shost_gendev, "trying to remove target %d:%d:0\n", bus, id);
+            vhba_scan_devices_remove(vhost, bus, id);
+        } else if (change > 0) {
+            dev_dbg(&vhost->shost->shost_gendev, "trying to add target %d:%d:0\n", bus, id);
+            vhba_scan_devices_add(vhost, bus, id);
+        } else {
+            /* quick sequence of add/remove or remove/add; we determine
+               which one it was by checking if device structure exists */
+            if (exists) {
+                /* remove followed by add: remove and (re)add */
+                dev_dbg(&vhost->shost->shost_gendev, "trying to (re)add target %d:%d:0\n", bus, id);
+                vhba_scan_devices_remove(vhost, bus, id);
+                vhba_scan_devices_add(vhost, bus, id);
+            } else {
+                /* add followed by remove: no-op */
+                dev_dbg(&vhost->shost->shost_gendev, "no-op for target %d:%d:0\n", bus, id);
+            }
+        }
+    }
+}
+
+static int vhba_add_device (struct vhba_device *vdev)
+{
+    struct vhba_host *vhost;
+    unsigned int devnum;
+    unsigned long flags;
+
+    vhost = platform_get_drvdata(&vhba_platform_device);
+
+    vhba_device_get(vdev);
+
+    spin_lock_irqsave(&vhost->dev_lock, flags);
+    if (vhost->num_devices >= VHBA_MAX_DEVICES) {
+        spin_unlock_irqrestore(&vhost->dev_lock, flags);
+        vhba_device_put(vdev);
+        return -EBUSY;
+    }
+
+    for (devnum = 0; devnum < VHBA_MAX_DEVICES; devnum++) {
+        if (vhost->devices[devnum] == NULL) {
+            vdev->num = devnum;
+            vhost->devices[devnum] = vdev;
+            vhost->num_devices++;
+            set_bit(devnum, vhost->chgmap);
+            vhost->chgtype[devnum]++;
+            break;
+        }
+    }
+    spin_unlock_irqrestore(&vhost->dev_lock, flags);
+
+    schedule_work(&vhost->scan_devices);
+
+    return 0;
+}
+
+static int vhba_remove_device (struct vhba_device *vdev)
+{
+    struct vhba_host *vhost;
+    unsigned long flags;
+
+    vhost = platform_get_drvdata(&vhba_platform_device);
+
+    spin_lock_irqsave(&vhost->dev_lock, flags);
+    set_bit(vdev->num, vhost->chgmap);
+    vhost->chgtype[vdev->num]--;
+    vhost->devices[vdev->num] = NULL;
+    vhost->num_devices--;
+    spin_unlock_irqrestore(&vhost->dev_lock, flags);
+
+    vhba_device_put(vdev);
+
+    schedule_work(&vhost->scan_devices);
+
+    return 0;
+}
+
+static struct vhba_device *vhba_lookup_device (int devnum)
+{
+    struct vhba_host *vhost;
+    struct vhba_device *vdev = NULL;
+    unsigned long flags;
+
+    vhost = platform_get_drvdata(&vhba_platform_device);
+
+    if (likely(devnum < VHBA_MAX_DEVICES)) {
+        spin_lock_irqsave(&vhost->dev_lock, flags);
+        vdev = vhost->devices[devnum];
+        if (vdev) {
+            vdev = vhba_device_get(vdev);
+        }
+
+        spin_unlock_irqrestore(&vhost->dev_lock, flags);
+    }
+
+    return vdev;
+}
+
+static struct vhba_command *vhba_alloc_command (void)
+{
+    struct vhba_host *vhost;
+    struct vhba_command *vcmd;
+    unsigned long flags;
+    int i;
+
+    vhost = platform_get_drvdata(&vhba_platform_device);
+
+    spin_lock_irqsave(&vhost->cmd_lock, flags);
+
+    vcmd = vhost->commands + vhost->cmd_next++;
+    if (vcmd->status != VHBA_REQ_FREE) {
+        for (i = 0; i < vhba_can_queue; i++) {
+            vcmd = vhost->commands + i;
+
+            if (vcmd->status == VHBA_REQ_FREE) {
+                vhost->cmd_next = i + 1;
+                break;
+            }
+        }
+
+        if (i == vhba_can_queue) {
+            vcmd = NULL;
+        }
+    }
+
+    if (vcmd) {
+        vcmd->status = VHBA_REQ_PENDING;
+    }
+
+    vhost->cmd_next %= vhba_can_queue;
+
+    spin_unlock_irqrestore(&vhost->cmd_lock, flags);
+
+    return vcmd;
+}
+
+static void vhba_free_command (struct vhba_command *vcmd)
+{
+    struct vhba_host *vhost;
+    unsigned long flags;
+
+    vhost = platform_get_drvdata(&vhba_platform_device);
+
+    spin_lock_irqsave(&vhost->cmd_lock, flags);
+    vcmd->status = VHBA_REQ_FREE;
+    spin_unlock_irqrestore(&vhost->cmd_lock, flags);
+}
+
+static int vhba_queuecommand (struct Scsi_Host *shost, struct scsi_cmnd *cmd)
+{
+    struct vhba_device *vdev;
+    int retval;
+    unsigned int devnum;
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 15, 0)
+    scmd_dbg(cmd, "queue %p tag %i\n", cmd, scsi_cmd_to_rq(cmd)->tag);
+#else
+    scmd_dbg(cmd, "queue %p tag %i\n", cmd, cmd->request->tag);
+#endif
+
+    devnum = bus_and_id_to_devnum(cmd->device->channel, cmd->device->id);
+    vdev = vhba_lookup_device(devnum);
+    if (!vdev) {
+        scmd_dbg(cmd, "no such device\n");
+
+        cmd->result = DID_NO_CONNECT << 16;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 16, 0)
+        scsi_done(cmd);
+#else
+        cmd->scsi_done(cmd);
+#endif
+
+        return 0;
+    }
+
+    retval = vhba_device_queue(vdev, cmd);
+
+    vhba_device_put(vdev);
+
+    return retval;
+}
+
+static int vhba_abort (struct scsi_cmnd *cmd)
+{
+    struct vhba_device *vdev;
+    int retval = SUCCESS;
+    unsigned int devnum;
+
+    scmd_dbg(cmd, "abort %p\n", cmd);
+
+    devnum = bus_and_id_to_devnum(cmd->device->channel, cmd->device->id);
+    vdev = vhba_lookup_device(devnum);
+    if (vdev) {
+        retval = vhba_device_dequeue(vdev, cmd);
+        vhba_device_put(vdev);
+    } else {
+        cmd->result = DID_NO_CONNECT << 16;
+    }
+
+    return retval;
+}
+
+static struct scsi_host_template vhba_template = {
+    .module = THIS_MODULE,
+    .name = "vhba",
+    .proc_name = "vhba",
+    .queuecommand = vhba_queuecommand,
+    .eh_abort_handler = vhba_abort,
+    .this_id = -1,
+    .max_sectors = VHBA_MAX_SECTORS_PER_IO,
+    .sg_tablesize = 256,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 19, 0)
+    .slave_alloc = vhba_slave_alloc,
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 0, 0)
+    .tag_alloc_policy = BLK_TAG_ALLOC_RR,
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) && LINUX_VERSION_CODE < KERNEL_VERSION(4, 4, 0)
+    .use_blk_tags = 1,
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0)
+    .max_segment_size = VHBA_KBUF_SIZE,
+#endif
+};
+
+static ssize_t do_request (struct vhba_device *vdev, unsigned long metatag, struct scsi_cmnd *cmd, char __user *buf, size_t buf_len)
+{
+    struct vhba_request vreq;
+    ssize_t ret;
+
+    scmd_dbg(cmd, "request %lu (%p), cdb 0x%x, bufflen %d, sg count %d\n",
+        metatag, cmd, cmd->cmnd[0], scsi_bufflen(cmd), scsi_sg_count(cmd));
+
+    ret = sizeof(vreq);
+    if (DATA_TO_DEVICE(cmd->sc_data_direction)) {
+        ret += scsi_bufflen(cmd);
+    }
+
+    if (ret > buf_len) {
+        scmd_dbg(cmd, "buffer too small (%zd < %zd) for a request\n", buf_len, ret);
+        return -EIO;
+    }
+
+    vreq.metatag = metatag;
+    vreq.lun = cmd->device->lun;
+    memcpy(vreq.cdb, cmd->cmnd, MAX_COMMAND_SIZE);
+    vreq.cdb_len = cmd->cmd_len;
+    vreq.data_len = scsi_bufflen(cmd);
+
+    if (copy_to_user(buf, &vreq, sizeof(vreq))) {
+        return -EFAULT;
+    }
+
+    if (DATA_TO_DEVICE(cmd->sc_data_direction) && vreq.data_len) {
+        buf += sizeof(vreq);
+
+        if (scsi_sg_count(cmd)) {
+            unsigned char *kaddr, *uaddr;
+            struct scatterlist *sglist = scsi_sglist(cmd);
+            struct scatterlist *sg;
+            int i;
+
+            uaddr = (unsigned char *) buf;
+
+            for_each_sg(sglist, sg, scsi_sg_count(cmd), i) {
+                size_t len = sg->length;
+
+                if (len > vdev->kbuf_size) {
+                    scmd_dbg(cmd, "segment size (%zu) exceeds kbuf size (%zu)!", len, vdev->kbuf_size);
+                    len = vdev->kbuf_size;
+                }
+
+                kaddr = kmap_atomic(sg_page(sg));
+                memcpy(vdev->kbuf, kaddr + sg->offset, len);
+                kunmap_atomic(kaddr);
+
+                if (copy_to_user(uaddr, vdev->kbuf, len)) {
+                    return -EFAULT;
+                }
+                uaddr += len;
+            }
+        } else {
+            if (copy_to_user(buf, scsi_sglist(cmd), vreq.data_len)) {
+                return -EFAULT;
+            }
+        }
+    }
+
+    return ret;
+}
+
+static ssize_t do_response (struct vhba_device *vdev, unsigned long metatag, struct scsi_cmnd *cmd, const char __user *buf, size_t buf_len, struct vhba_response *res)
+{
+    ssize_t ret = 0;
+
+    scmd_dbg(cmd, "response %lu (%p), status %x, data len %d, sg count %d\n",
+         metatag, cmd, res->status, res->data_len, scsi_sg_count(cmd));
+
+    if (res->status) {
+        if (res->data_len > SCSI_SENSE_BUFFERSIZE) {
+            scmd_dbg(cmd, "truncate sense (%d < %d)", SCSI_SENSE_BUFFERSIZE, res->data_len);
+            res->data_len = SCSI_SENSE_BUFFERSIZE;
+        }
+
+        if (copy_from_user(cmd->sense_buffer, buf, res->data_len)) {
+            return -EFAULT;
+        }
+
+        cmd->result = res->status;
+
+        ret += res->data_len;
+    } else if (DATA_FROM_DEVICE(cmd->sc_data_direction) && scsi_bufflen(cmd)) {
+        size_t to_read;
+
+        if (res->data_len > scsi_bufflen(cmd)) {
+            scmd_dbg(cmd, "truncate data (%d < %d)\n", scsi_bufflen(cmd), res->data_len);
+            res->data_len = scsi_bufflen(cmd);
+        }
+
+        to_read = res->data_len;
+
+        if (scsi_sg_count(cmd)) {
+            unsigned char *kaddr, *uaddr;
+            struct scatterlist *sglist = scsi_sglist(cmd);
+            struct scatterlist *sg;
+            int i;
+
+            uaddr = (unsigned char *)buf;
+
+            for_each_sg(sglist, sg, scsi_sg_count(cmd), i) {
+                size_t len = (sg->length < to_read) ? sg->length : to_read;
+
+                if (len > vdev->kbuf_size) {
+                    scmd_dbg(cmd, "segment size (%zu) exceeds kbuf size (%zu)!", len, vdev->kbuf_size);
+                    len = vdev->kbuf_size;
+                }
+
+                if (copy_from_user(vdev->kbuf, uaddr, len)) {
+                    return -EFAULT;
+                }
+                uaddr += len;
+
+                kaddr = kmap_atomic(sg_page(sg));
+                memcpy(kaddr + sg->offset, vdev->kbuf, len);
+                kunmap_atomic(kaddr);
+
+                to_read -= len;
+                if (to_read == 0) {
+                    break;
+                }
+            }
+        } else {
+            if (copy_from_user(scsi_sglist(cmd), buf, res->data_len)) {
+                return -EFAULT;
+            }
+
+            to_read -= res->data_len;
+        }
+
+        scsi_set_resid(cmd, to_read);
+
+        ret += res->data_len - to_read;
+    }
+
+    return ret;
+}
+
+static struct vhba_command *next_command (struct vhba_device *vdev)
+{
+    struct vhba_command *vcmd;
+
+    list_for_each_entry(vcmd, &vdev->cmd_list, entry) {
+        if (vcmd->status == VHBA_REQ_PENDING) {
+            break;
+        }
+    }
+
+    if (&vcmd->entry == &vdev->cmd_list) {
+        vcmd = NULL;
+    }
+
+    return vcmd;
+}
+
+static struct vhba_command *match_command (struct vhba_device *vdev, __u32 metatag)
+{
+    struct vhba_command *vcmd;
+
+    list_for_each_entry(vcmd, &vdev->cmd_list, entry) {
+        if (vcmd->metatag == metatag) {
+            break;
+        }
+    }
+
+    if (&vcmd->entry == &vdev->cmd_list) {
+        vcmd = NULL;
+    }
+
+    return vcmd;
+}
+
+static struct vhba_command *wait_command (struct vhba_device *vdev, unsigned long flags)
+{
+    struct vhba_command *vcmd;
+    DEFINE_WAIT(wait);
+
+    while (!(vcmd = next_command(vdev))) {
+        if (signal_pending(current)) {
+            break;
+        }
+
+        prepare_to_wait(&vdev->cmd_wq, &wait, TASK_INTERRUPTIBLE);
+
+        spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+        schedule();
+
+        spin_lock_irqsave(&vdev->cmd_lock, flags);
+    }
+
+    finish_wait(&vdev->cmd_wq, &wait);
+    if (vcmd) {
+        vcmd->status = VHBA_REQ_READING;
+    }
+
+    return vcmd;
+}
+
+static ssize_t vhba_ctl_read (struct file *file, char __user *buf, size_t buf_len, loff_t *offset)
+{
+    struct vhba_device *vdev;
+    struct vhba_command *vcmd;
+    ssize_t ret;
+    unsigned long flags;
+
+    vdev = file->private_data;
+
+    /* Get next command */
+    if (file->f_flags & O_NONBLOCK) {
+        /* Non-blocking variant */
+        spin_lock_irqsave(&vdev->cmd_lock, flags);
+        vcmd = next_command(vdev);
+        spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+        if (!vcmd) {
+            return -EWOULDBLOCK;
+        }
+    } else {
+        /* Blocking variant */
+        spin_lock_irqsave(&vdev->cmd_lock, flags);
+        vcmd = wait_command(vdev, flags);
+        spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+        if (!vcmd) {
+            return -ERESTARTSYS;
+        }
+    }
+
+    ret = do_request(vdev, vcmd->metatag, vcmd->cmd, buf, buf_len);
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+    if (ret >= 0) {
+        vcmd->status = VHBA_REQ_SENT;
+        *offset += ret;
+    } else {
+        vcmd->status = VHBA_REQ_PENDING;
+    }
+
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    return ret;
+}
+
+static ssize_t vhba_ctl_write (struct file *file, const char __user *buf, size_t buf_len, loff_t *offset)
+{
+    struct vhba_device *vdev;
+    struct vhba_command *vcmd;
+    struct vhba_response res;
+    ssize_t ret;
+    unsigned long flags;
+
+    if (buf_len < sizeof(res)) {
+        return -EIO;
+    }
+
+    if (copy_from_user(&res, buf, sizeof(res))) {
+        return -EFAULT;
+    }
+
+    vdev = file->private_data;
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+    vcmd = match_command(vdev, res.metatag);
+    if (!vcmd || vcmd->status != VHBA_REQ_SENT) {
+        spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+        pr_debug("ctl dev #%u not expecting response\n", vdev->num);
+        return -EIO;
+    }
+    vcmd->status = VHBA_REQ_WRITING;
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    ret = do_response(vdev, vcmd->metatag, vcmd->cmd, buf + sizeof(res), buf_len - sizeof(res), &res);
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+    if (ret >= 0) {
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 16, 0)
+        scsi_done(vcmd->cmd);
+#else
+        vcmd->cmd->scsi_done(vcmd->cmd);
+#endif
+        ret += sizeof(res);
+
+        /* don't compete with vhba_device_dequeue */
+        if (!list_empty(&vcmd->entry)) {
+            list_del_init(&vcmd->entry);
+            vhba_free_command(vcmd);
+        }
+    } else {
+        vcmd->status = VHBA_REQ_SENT;
+    }
+
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    return ret;
+}
+
+static long vhba_ctl_ioctl (struct file *file, unsigned int cmd, unsigned long arg)
+{
+    struct vhba_device *vdev = file->private_data;
+    struct vhba_host *vhost = platform_get_drvdata(&vhba_platform_device);
+
+    switch (cmd) {
+        case 0xBEEF001: {
+            unsigned int ident[4]; /* host, channel, id, lun */
+
+            ident[0] = vhost->shost->host_no;
+            devnum_to_bus_and_id(vdev->num, &ident[1], &ident[2]);
+            ident[3] = 0; /* lun */
+
+            if (copy_to_user((void *) arg, ident, sizeof(ident))) {
+                return -EFAULT;
+            }
+
+            return 0;
+        }
+        case 0xBEEF002: {
+            unsigned int devnum = vdev->num;
+
+            if (copy_to_user((void *) arg, &devnum, sizeof(devnum))) {
+                return -EFAULT;
+            }
+
+            return 0;
+        }
+    }
+
+    return -ENOTTY;
+}
+
+#ifdef CONFIG_COMPAT
+static long vhba_ctl_compat_ioctl (struct file *file, unsigned int cmd, unsigned long arg)
+{
+    unsigned long compat_arg = (unsigned long)compat_ptr(arg);
+    return vhba_ctl_ioctl(file, cmd, compat_arg);
+}
+#endif
+
+static unsigned int vhba_ctl_poll (struct file *file, poll_table *wait)
+{
+    struct vhba_device *vdev = file->private_data;
+    unsigned int mask = 0;
+    unsigned long flags;
+
+    poll_wait(file, &vdev->cmd_wq, wait);
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+    if (next_command(vdev)) {
+        mask |= POLLIN | POLLRDNORM;
+    }
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    return mask;
+}
+
+static int vhba_ctl_open (struct inode *inode, struct file *file)
+{
+    struct vhba_device *vdev;
+    int retval;
+
+    pr_debug("ctl dev open\n");
+
+    /* check if vhba is probed */
+    if (!platform_get_drvdata(&vhba_platform_device)) {
+        return -ENODEV;
+    }
+
+    vdev = vhba_device_alloc();
+    if (!vdev) {
+        return -ENOMEM;
+    }
+
+    vdev->kbuf_size = VHBA_KBUF_SIZE;
+    vdev->kbuf = kzalloc(vdev->kbuf_size, GFP_KERNEL);
+    if (!vdev->kbuf) {
+        return -ENOMEM;
+    }
+
+    if (!(retval = vhba_add_device(vdev))) {
+        file->private_data = vdev;
+    }
+
+    vhba_device_put(vdev);
+
+    return retval;
+}
+
+static int vhba_ctl_release (struct inode *inode, struct file *file)
+{
+    struct vhba_device *vdev;
+    struct vhba_command *vcmd;
+    unsigned long flags;
+
+    vdev = file->private_data;
+
+    pr_debug("ctl dev release\n");
+
+    vhba_device_get(vdev);
+    vhba_remove_device(vdev);
+
+    spin_lock_irqsave(&vdev->cmd_lock, flags);
+    list_for_each_entry(vcmd, &vdev->cmd_list, entry) {
+        WARN_ON(vcmd->status == VHBA_REQ_READING || vcmd->status == VHBA_REQ_WRITING);
+
+        scmd_dbg(vcmd->cmd, "device released with command %lu (%p)\n", vcmd->metatag, vcmd->cmd);
+        vcmd->cmd->result = DID_NO_CONNECT << 16;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 16, 0)
+        scsi_done(vcmd->cmd);
+#else
+        vcmd->cmd->scsi_done(vcmd->cmd);
+#endif
+        vhba_free_command(vcmd);
+    }
+    INIT_LIST_HEAD(&vdev->cmd_list);
+    spin_unlock_irqrestore(&vdev->cmd_lock, flags);
+
+    kfree(vdev->kbuf);
+    vdev->kbuf = NULL;
+
+    vhba_device_put(vdev);
+
+    return 0;
+}
+
+static struct file_operations vhba_ctl_fops = {
+    .owner = THIS_MODULE,
+    .open = vhba_ctl_open,
+    .release = vhba_ctl_release,
+    .read = vhba_ctl_read,
+    .write = vhba_ctl_write,
+    .poll = vhba_ctl_poll,
+    .unlocked_ioctl = vhba_ctl_ioctl,
+#ifdef CONFIG_COMPAT
+    .compat_ioctl = vhba_ctl_compat_ioctl,
+#endif
+};
+
+static struct miscdevice vhba_miscdev = {
+    .minor = MISC_DYNAMIC_MINOR,
+    .name = "vhba_ctl",
+    .fops = &vhba_ctl_fops,
+};
+
+static int vhba_probe (struct platform_device *pdev)
+{
+    struct Scsi_Host *shost;
+    struct vhba_host *vhost;
+    int i;
+
+    vhba_can_queue = clamp(vhba_can_queue, 1, 256);
+
+    shost = scsi_host_alloc(&vhba_template, sizeof(struct vhba_host));
+    if (!shost) {
+        return -ENOMEM;
+    }
+
+    shost->max_channel = VHBA_MAX_BUS-1;
+    shost->max_id = VHBA_MAX_ID;
+    /* we don't support lun > 0 */
+    shost->max_lun = 1;
+    shost->max_cmd_len = MAX_COMMAND_SIZE;
+    shost->can_queue = vhba_can_queue;
+    shost->cmd_per_lun = vhba_can_queue;
+
+    vhost = (struct vhba_host *)shost->hostdata;
+    memset(vhost, 0, sizeof(struct vhba_host));
+
+    vhost->shost = shost;
+    vhost->num_devices = 0;
+    spin_lock_init(&vhost->dev_lock);
+    spin_lock_init(&vhost->cmd_lock);
+    INIT_WORK(&vhost->scan_devices, vhba_scan_devices);
+    vhost->cmd_next = 0;
+    vhost->commands = kzalloc(vhba_can_queue * sizeof(struct vhba_command), GFP_KERNEL);
+    if (!vhost->commands) {
+        return -ENOMEM;
+    }
+
+    for (i = 0; i < vhba_can_queue; i++) {
+        vhost->commands[i].status = VHBA_REQ_FREE;
+    }
+
+    platform_set_drvdata(pdev, vhost);
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 4, 0)
+    i = scsi_init_shared_tag_map(shost, vhba_can_queue);
+    if (i) return i;
+#endif
+
+    if (scsi_add_host(shost, &pdev->dev)) {
+        scsi_host_put(shost);
+        return -ENOMEM;
+    }
+
+    return 0;
+}
+
+static int vhba_remove (struct platform_device *pdev)
+{
+    struct vhba_host *vhost;
+    struct Scsi_Host *shost;
+
+    vhost = platform_get_drvdata(pdev);
+    shost = vhost->shost;
+
+    scsi_remove_host(shost);
+    scsi_host_put(shost);
+
+    kfree(vhost->commands);
+
+    return 0;
+}
+
+static void vhba_release (struct device * dev)
+{
+    return;
+}
+
+static struct platform_device vhba_platform_device = {
+    .name = "vhba",
+    .id = -1,
+    .dev = {
+        .release = vhba_release,
+    },
+};
+
+static struct platform_driver vhba_platform_driver = {
+    .driver = {
+        .owner = THIS_MODULE,
+        .name = "vhba",
+    },
+    .probe = vhba_probe,
+    .remove = vhba_remove,
+};
+
+static int __init vhba_init (void)
+{
+    int ret;
+
+    ret = platform_device_register(&vhba_platform_device);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = platform_driver_register(&vhba_platform_driver);
+    if (ret < 0) {
+        platform_device_unregister(&vhba_platform_device);
+        return ret;
+    }
+
+    ret = misc_register(&vhba_miscdev);
+    if (ret < 0) {
+        platform_driver_unregister(&vhba_platform_driver);
+        platform_device_unregister(&vhba_platform_device);
+        return ret;
+    }
+
+    return 0;
+}
+
+static void __exit vhba_exit(void)
+{
+    misc_deregister(&vhba_miscdev);
+    platform_driver_unregister(&vhba_platform_driver);
+    platform_device_unregister(&vhba_platform_device);
+}
+
+module_init(vhba_init);
+module_exit(vhba_exit);
+