370 lines
8.9 KiB
C
370 lines
8.9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* HMC Drive CD/DVD Device
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*
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* Copyright IBM Corp. 2013
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* Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
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*
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* This file provides a Linux "misc" character device for access to an
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* assigned HMC drive CD/DVD-ROM. It works as follows: First create the
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* device by calling hmcdrv_dev_init(). After open() a lseek(fd, 0,
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* SEEK_END) indicates that a new FTP command follows (not needed on the
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* first command after open). Then write() the FTP command ASCII string
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* to it, e.g. "dir /" or "nls <directory>" or "get <filename>". At the
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* end read() the response.
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*/
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#define KMSG_COMPONENT "hmcdrv"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/cdev.h>
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#include <linux/miscdevice.h>
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#include <linux/device.h>
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#include <linux/capability.h>
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#include <linux/delay.h>
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#include <linux/uaccess.h>
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#include "hmcdrv_dev.h"
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#include "hmcdrv_ftp.h"
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/* If the following macro is defined, then the HMC device creates it's own
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* separated device class (and dynamically assigns a major number). If not
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* defined then the HMC device is assigned to the "misc" class devices.
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*
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#define HMCDRV_DEV_CLASS "hmcftp"
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*/
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#define HMCDRV_DEV_NAME "hmcdrv"
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#define HMCDRV_DEV_BUSY_DELAY 500 /* delay between -EBUSY trials in ms */
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#define HMCDRV_DEV_BUSY_RETRIES 3 /* number of retries on -EBUSY */
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struct hmcdrv_dev_node {
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#ifdef HMCDRV_DEV_CLASS
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struct cdev dev; /* character device structure */
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umode_t mode; /* mode of device node (unused, zero) */
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#else
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struct miscdevice dev; /* "misc" device structure */
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#endif
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};
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static int hmcdrv_dev_open(struct inode *inode, struct file *fp);
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static int hmcdrv_dev_release(struct inode *inode, struct file *fp);
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static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence);
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static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
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size_t len, loff_t *pos);
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static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
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size_t len, loff_t *pos);
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static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
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char __user *buf, size_t len);
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/*
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* device operations
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*/
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static const struct file_operations hmcdrv_dev_fops = {
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.open = hmcdrv_dev_open,
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.llseek = hmcdrv_dev_seek,
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.release = hmcdrv_dev_release,
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.read = hmcdrv_dev_read,
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.write = hmcdrv_dev_write,
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};
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static struct hmcdrv_dev_node hmcdrv_dev; /* HMC device struct (static) */
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#ifdef HMCDRV_DEV_CLASS
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static struct class *hmcdrv_dev_class; /* device class pointer */
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static dev_t hmcdrv_dev_no; /* device number (major/minor) */
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/**
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* hmcdrv_dev_name() - provides a naming hint for a device node in /dev
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* @dev: device for which the naming/mode hint is
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* @mode: file mode for device node created in /dev
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*
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* See: devtmpfs.c, function devtmpfs_create_node()
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*
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* Return: recommended device file name in /dev
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*/
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static char *hmcdrv_dev_name(struct device *dev, umode_t *mode)
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{
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char *nodename = NULL;
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const char *devname = dev_name(dev); /* kernel device name */
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if (devname)
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nodename = kasprintf(GFP_KERNEL, "%s", devname);
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/* on device destroy (rmmod) the mode pointer may be NULL
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*/
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if (mode)
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*mode = hmcdrv_dev.mode;
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return nodename;
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}
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#endif /* HMCDRV_DEV_CLASS */
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/*
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* open()
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*/
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static int hmcdrv_dev_open(struct inode *inode, struct file *fp)
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{
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int rc;
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/* check for non-blocking access, which is really unsupported
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*/
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if (fp->f_flags & O_NONBLOCK)
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return -EINVAL;
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/* Because it makes no sense to open this device read-only (then a
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* FTP command cannot be emitted), we respond with an error.
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*/
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if ((fp->f_flags & O_ACCMODE) == O_RDONLY)
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return -EINVAL;
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/* prevent unloading this module as long as anyone holds the
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* device file open - so increment the reference count here
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*/
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if (!try_module_get(THIS_MODULE))
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return -ENODEV;
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fp->private_data = NULL; /* no command yet */
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rc = hmcdrv_ftp_startup();
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if (rc)
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module_put(THIS_MODULE);
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pr_debug("open file '/dev/%pD' with return code %d\n", fp, rc);
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return rc;
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}
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/*
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* release()
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*/
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static int hmcdrv_dev_release(struct inode *inode, struct file *fp)
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{
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pr_debug("closing file '/dev/%pD'\n", fp);
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kfree(fp->private_data);
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fp->private_data = NULL;
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hmcdrv_ftp_shutdown();
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module_put(THIS_MODULE);
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return 0;
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}
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/*
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* lseek()
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*/
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static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence)
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{
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switch (whence) {
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case SEEK_CUR: /* relative to current file position */
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pos += fp->f_pos; /* new position stored in 'pos' */
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break;
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case SEEK_SET: /* absolute (relative to beginning of file) */
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break; /* SEEK_SET */
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/* We use SEEK_END as a special indicator for a SEEK_SET
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* (set absolute position), combined with a FTP command
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* clear.
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*/
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case SEEK_END:
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if (fp->private_data) {
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kfree(fp->private_data);
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fp->private_data = NULL;
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}
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break; /* SEEK_END */
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default: /* SEEK_DATA, SEEK_HOLE: unsupported */
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return -EINVAL;
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}
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if (pos < 0)
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return -EINVAL;
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if (fp->f_pos != pos)
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++fp->f_version;
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fp->f_pos = pos;
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return pos;
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}
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/*
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* transfer (helper function)
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*/
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static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
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char __user *buf, size_t len)
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{
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ssize_t retlen;
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unsigned trials = HMCDRV_DEV_BUSY_RETRIES;
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do {
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retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);
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if (retlen != -EBUSY)
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break;
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msleep(HMCDRV_DEV_BUSY_DELAY);
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} while (--trials > 0);
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return retlen;
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}
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/*
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* read()
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*/
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static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
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size_t len, loff_t *pos)
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{
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ssize_t retlen;
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if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||
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(fp->private_data == NULL)) { /* no FTP cmd defined ? */
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return -EBADF;
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}
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retlen = hmcdrv_dev_transfer((char *) fp->private_data,
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*pos, ubuf, len);
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pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n",
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fp, (long long) *pos, retlen, len);
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if (retlen > 0)
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*pos += retlen;
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return retlen;
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}
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/*
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* write()
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*/
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static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
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size_t len, loff_t *pos)
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{
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ssize_t retlen;
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pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n",
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fp, (long long) *pos, len);
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if (!fp->private_data) { /* first expect a cmd write */
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fp->private_data = kmalloc(len + 1, GFP_KERNEL);
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if (!fp->private_data)
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return -ENOMEM;
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if (!copy_from_user(fp->private_data, ubuf, len)) {
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((char *)fp->private_data)[len] = '\0';
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return len;
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}
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kfree(fp->private_data);
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fp->private_data = NULL;
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return -EFAULT;
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}
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retlen = hmcdrv_dev_transfer((char *) fp->private_data,
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*pos, (char __user *) ubuf, len);
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if (retlen > 0)
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*pos += retlen;
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pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen);
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return retlen;
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}
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/**
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* hmcdrv_dev_init() - creates a HMC drive CD/DVD device
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*
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* This function creates a HMC drive CD/DVD kernel device and an associated
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* device under /dev, using a dynamically allocated major number.
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*
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* Return: 0 on success, else an error code.
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*/
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int hmcdrv_dev_init(void)
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{
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int rc;
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#ifdef HMCDRV_DEV_CLASS
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struct device *dev;
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rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);
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if (rc)
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goto out_err;
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cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);
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hmcdrv_dev.dev.owner = THIS_MODULE;
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rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);
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if (rc)
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goto out_unreg;
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/* At this point the character device exists in the kernel (see
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* /proc/devices), but not under /dev nor /sys/devices/virtual. So
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* we have to create an associated class (see /sys/class).
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*/
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hmcdrv_dev_class = class_create(THIS_MODULE, HMCDRV_DEV_CLASS);
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if (IS_ERR(hmcdrv_dev_class)) {
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rc = PTR_ERR(hmcdrv_dev_class);
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goto out_devdel;
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}
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/* Finally a device node in /dev has to be established (as 'mkdev'
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* does from the command line). Notice that assignment of a device
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* node name/mode function is optional (only for mode != 0600).
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*/
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hmcdrv_dev.mode = 0; /* "unset" */
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hmcdrv_dev_class->devnode = hmcdrv_dev_name;
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dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,
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"%s", HMCDRV_DEV_NAME);
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if (!IS_ERR(dev))
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return 0;
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rc = PTR_ERR(dev);
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class_destroy(hmcdrv_dev_class);
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hmcdrv_dev_class = NULL;
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out_devdel:
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cdev_del(&hmcdrv_dev.dev);
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out_unreg:
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unregister_chrdev_region(hmcdrv_dev_no, 1);
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out_err:
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#else /* !HMCDRV_DEV_CLASS */
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hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;
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hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;
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hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;
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hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */
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rc = misc_register(&hmcdrv_dev.dev);
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#endif /* HMCDRV_DEV_CLASS */
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return rc;
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}
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/**
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* hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device
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*/
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void hmcdrv_dev_exit(void)
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{
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#ifdef HMCDRV_DEV_CLASS
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if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {
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device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);
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class_destroy(hmcdrv_dev_class);
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}
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cdev_del(&hmcdrv_dev.dev);
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unregister_chrdev_region(hmcdrv_dev_no, 1);
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#else /* !HMCDRV_DEV_CLASS */
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misc_deregister(&hmcdrv_dev.dev);
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#endif /* HMCDRV_DEV_CLASS */
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}
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