s390/hmcdrv: HMC drive CD/DVD access

This device driver allows accessing a HMC drive CD/DVD-ROM.
It can be used in a LPAR and z/VM environment.

Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ralf Hoppe <rhoppe@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 370 insertions, 0 deletions

diff --git a/drivers/s390/char/hmcdrv_dev.c b/drivers/s390/char/hmcdrv_dev.c
new file mode 100644
index 000000000000..0c5176179c17
--- /dev/null
+++ b/drivers/s390/char/hmcdrv_dev.c
@@ -0,0 +1,370 @@
+/*
+ *    HMC Drive CD/DVD Device
+ *
+ *    Copyright IBM Corp. 2013
+ *    Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
+ *
+ *    This file provides a Linux "misc" character device for access to an
+ *    assigned HMC drive CD/DVD-ROM. It works as follows: First create the
+ *    device by calling hmcdrv_dev_init(). After open() a lseek(fd, 0,
+ *    SEEK_END) indicates that a new FTP command follows (not needed on the
+ *    first command after open). Then write() the FTP command ASCII string
+ *    to it, e.g. "dir /" or "nls <directory>" or "get <filename>". At the
+ *    end read() the response.
+ */
+
+#define KMSG_COMPONENT "hmcdrv"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <linux/miscdevice.h>
+#include <linux/device.h>
+#include <linux/capability.h>
+#include <linux/delay.h>
+#include <linux/uaccess.h>
+
+#include "hmcdrv_dev.h"
+#include "hmcdrv_ftp.h"
+
+/* If the following macro is defined, then the HMC device creates it's own
+ * separated device class (and dynamically assigns a major number). If not
+ * defined then the HMC device is assigned to the "misc" class devices.
+ *
+#define HMCDRV_DEV_CLASS "hmcftp"
+ */
+
+#define HMCDRV_DEV_NAME  "hmcdrv"
+#define HMCDRV_DEV_BUSY_DELAY    500 /* delay between -EBUSY trials in ms */
+#define HMCDRV_DEV_BUSY_RETRIES  3   /* number of retries on -EBUSY */
+
+struct hmcdrv_dev_node {
+
+#ifdef HMCDRV_DEV_CLASS
+        struct cdev dev; /* character device structure */
+        umode_t mode;    /* mode of device node (unused, zero) */
+#else
+        struct miscdevice dev; /* "misc" device structure */
+#endif
+
+};
+
+static int hmcdrv_dev_open(struct inode *inode, struct file *fp);
+static int hmcdrv_dev_release(struct inode *inode, struct file *fp);
+static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence);
+static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
+                               size_t len, loff_t *pos);
+static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
+                                size_t len, loff_t *pos);
+static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
+                                   char __user *buf, size_t len);
+
+/*
+ * device operations
+ */
+static const struct file_operations hmcdrv_dev_fops = {
+        .open = hmcdrv_dev_open,
+        .llseek = hmcdrv_dev_seek,
+        .release = hmcdrv_dev_release,
+        .read = hmcdrv_dev_read,
+        .write = hmcdrv_dev_write,
+};
+
+static struct hmcdrv_dev_node hmcdrv_dev; /* HMC device struct (static) */
+
+#ifdef HMCDRV_DEV_CLASS
+
+static struct class *hmcdrv_dev_class; /* device class pointer */
+static dev_t hmcdrv_dev_no; /* device number (major/minor) */
+
+/**
+ * hmcdrv_dev_name() - provides a naming hint for a device node in /dev
+ * @dev: device for which the naming/mode hint is
+ * @mode: file mode for device node created in /dev
+ *
+ * See: devtmpfs.c, function devtmpfs_create_node()
+ *
+ * Return: recommended device file name in /dev
+ */
+static char *hmcdrv_dev_name(struct device *dev, umode_t *mode)
+{
+        char *nodename = NULL;
+        const char *devname = dev_name(dev); /* kernel device name */
+
+        if (devname)
+                nodename = kasprintf(GFP_KERNEL, "%s", devname);
+
+        /* on device destroy (rmmod) the mode pointer may be NULL
+         */
+        if (mode)
+                *mode = hmcdrv_dev.mode;
+
+        return nodename;
+}
+
+#endif  /* HMCDRV_DEV_CLASS */
+
+/*
+ * open()
+ */
+static int hmcdrv_dev_open(struct inode *inode, struct file *fp)
+{
+        int rc;
+
+        /* check for non-blocking access, which is really unsupported
+         */
+        if (fp->f_flags & O_NONBLOCK)
+                return -EINVAL;
+
+        /* Because it makes no sense to open this device read-only (then a
+         * FTP command cannot be emitted), we respond with an error.
+         */
+        if ((fp->f_flags & O_ACCMODE) == O_RDONLY)
+                return -EINVAL;
+
+        /* prevent unloading this module as long as anyone holds the
+         * device file open - so increment the reference count here
+         */
+        if (!try_module_get(THIS_MODULE))
+                return -ENODEV;
+
+        fp->private_data = NULL; /* no command yet */
+        rc = hmcdrv_ftp_startup();
+        if (rc)
+                module_put(THIS_MODULE);
+
+        pr_debug("open file '/dev/%s' with return code %d\n",
+                 fp->f_dentry->d_name.name, rc);
+        return rc;
+}
+
+/*
+ * release()
+ */
+static int hmcdrv_dev_release(struct inode *inode, struct file *fp)
+{
+        pr_debug("closing file '/dev/%s'\n", fp->f_dentry->d_name.name);
+        kfree(fp->private_data);
+        fp->private_data = NULL;
+        hmcdrv_ftp_shutdown();
+        module_put(THIS_MODULE);
+        return 0;
+}
+
+/*
+ * lseek()
+ */
+static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence)
+{
+        switch (whence) {
+        case SEEK_CUR: /* relative to current file position */
+                pos += fp->f_pos; /* new position stored in 'pos' */
+                break;
+
+        case SEEK_SET: /* absolute (relative to beginning of file) */
+                break; /* SEEK_SET */
+
+                /* We use SEEK_END as a special indicator for a SEEK_SET
+                 * (set absolute position), combined with a FTP command
+                 * clear.
+                 */
+        case SEEK_END:
+                if (fp->private_data) {
+                        kfree(fp->private_data);
+                        fp->private_data = NULL;
+                }
+
+                break; /* SEEK_END */
+
+        default: /* SEEK_DATA, SEEK_HOLE: unsupported */
+                return -EINVAL;
+        }
+
+        if (pos < 0)
+                return -EINVAL;
+
+        if (fp->f_pos != pos)
+                ++fp->f_version;
+
+        fp->f_pos = pos;
+        return pos;
+}
+
+/*
+ * transfer (helper function)
+ */
+static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
+                                   char __user *buf, size_t len)
+{
+        ssize_t retlen;
+        unsigned trials = HMCDRV_DEV_BUSY_RETRIES;
+
+        do {
+                retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);
+
+                if (retlen != -EBUSY)
+                        break;
+
+                msleep(HMCDRV_DEV_BUSY_DELAY);
+
+        } while (--trials > 0);
+
+        return retlen;
+}
+
+/*
+ * read()
+ */
+static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
+                               size_t len, loff_t *pos)
+{
+        ssize_t retlen;
+
+        if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||
+            (fp->private_data == NULL)) { /* no FTP cmd defined ? */
+                return -EBADF;
+        }
+
+        retlen = hmcdrv_dev_transfer((char *) fp->private_data,
+                                     *pos, ubuf, len);
+
+        pr_debug("read from file '/dev/%s' at %lld returns %zd/%zu\n",
+                 fp->f_dentry->d_name.name, (long long) *pos, retlen, len);
+
+        if (retlen > 0)
+                *pos += retlen;
+
+        return retlen;
+}
+
+/*
+ * write()
+ */
+static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
+                                size_t len, loff_t *pos)
+{
+        ssize_t retlen;
+
+        pr_debug("writing file '/dev/%s' at pos. %lld with length %zd\n",
+                 fp->f_dentry->d_name.name, (long long) *pos, len);
+
+        if (!fp->private_data) { /* first expect a cmd write */
+                fp->private_data = kmalloc(len + 1, GFP_KERNEL);
+
+                if (!fp->private_data)
+                        return -ENOMEM;
+
+                if (!copy_from_user(fp->private_data, ubuf, len)) {
+                        ((char *)fp->private_data)[len] = '\0';
+                        return len;
+                }
+
+                kfree(fp->private_data);
+                fp->private_data = NULL;
+                return -EFAULT;
+        }
+
+        retlen = hmcdrv_dev_transfer((char *) fp->private_data,
+                                     *pos, (char __user *) ubuf, len);
+        if (retlen > 0)
+                *pos += retlen;
+
+        pr_debug("write to file '/dev/%s' returned %zd\n",
+                 fp->f_dentry->d_name.name, retlen);
+
+        return retlen;
+}
+
+/**
+ * hmcdrv_dev_init() - creates a HMC drive CD/DVD device
+ *
+ * This function creates a HMC drive CD/DVD kernel device and an associated
+ * device under /dev, using a dynamically allocated major number.
+ *
+ * Return: 0 on success, else an error code.
+ */
+int hmcdrv_dev_init(void)
+{
+        int rc;
+
+#ifdef HMCDRV_DEV_CLASS
+        struct device *dev;
+
+        rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);
+
+        if (rc)
+                goto out_err;
+
+        cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);
+        hmcdrv_dev.dev.owner = THIS_MODULE;
+        rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);
+
+        if (rc)
+                goto out_unreg;
+
+        /* At this point the character device exists in the kernel (see
+         * /proc/devices), but not under /dev nor /sys/devices/virtual. So
+         * we have to create an associated class (see /sys/class).
+         */
+        hmcdrv_dev_class = class_create(THIS_MODULE, HMCDRV_DEV_CLASS);
+
+        if (IS_ERR(hmcdrv_dev_class)) {
+                rc = PTR_ERR(hmcdrv_dev_class);
+                goto out_devdel;
+        }
+
+        /* Finally a device node in /dev has to be established (as 'mkdev'
+         * does from the command line). Notice that assignment of a device
+         * node name/mode function is optional (only for mode != 0600).
+         */
+        hmcdrv_dev.mode = 0; /* "unset" */
+        hmcdrv_dev_class->devnode = hmcdrv_dev_name;
+
+        dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,
+                            "%s", HMCDRV_DEV_NAME);
+        if (!IS_ERR(dev))
+                return 0;
+
+        rc = PTR_ERR(dev);
+        class_destroy(hmcdrv_dev_class);
+        hmcdrv_dev_class = NULL;
+
+out_devdel:
+        cdev_del(&hmcdrv_dev.dev);
+
+out_unreg:
+        unregister_chrdev_region(hmcdrv_dev_no, 1);
+
+out_err:
+
+#else  /* !HMCDRV_DEV_CLASS */
+        hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;
+        hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;
+        hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;
+        hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */
+        rc = misc_register(&hmcdrv_dev.dev);
+#endif  /* HMCDRV_DEV_CLASS */
+
+        return rc;
+}
+
+/**
+ * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device
+ */
+void hmcdrv_dev_exit(void)
+{
+#ifdef HMCDRV_DEV_CLASS
+        if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {
+                device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);
+                class_destroy(hmcdrv_dev_class);
+        }
+
+        cdev_del(&hmcdrv_dev.dev);
+        unregister_chrdev_region(hmcdrv_dev_no, 1);
+#else  /* !HMCDRV_DEV_CLASS */
+        misc_deregister(&hmcdrv_dev.dev);
+#endif  /* HMCDRV_DEV_CLASS */
+}