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 00000000000..0c5176179c1
--- /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 */
+}