367 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * HMC Drive CD/DVD Device4 *5 * Copyright IBM Corp. 20136 * Author(s): Ralf Hoppe (rhoppe@de.ibm.com)7 *8 * This file provides a Linux "misc" character device for access to an9 * assigned HMC drive CD/DVD-ROM. It works as follows: First create the10 * device by calling hmcdrv_dev_init(). After open() a lseek(fd, 0,11 * SEEK_END) indicates that a new FTP command follows (not needed on the12 * first command after open). Then write() the FTP command ASCII string13 * to it, e.g. "dir /" or "nls <directory>" or "get <filename>". At the14 * end read() the response.15 */16 17#define KMSG_COMPONENT "hmcdrv"18#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt19 20#include <linux/kernel.h>21#include <linux/module.h>22#include <linux/slab.h>23#include <linux/fs.h>24#include <linux/cdev.h>25#include <linux/miscdevice.h>26#include <linux/device.h>27#include <linux/capability.h>28#include <linux/delay.h>29#include <linux/uaccess.h>30 31#include "hmcdrv_dev.h"32#include "hmcdrv_ftp.h"33 34/* If the following macro is defined, then the HMC device creates it's own35 * separated device class (and dynamically assigns a major number). If not36 * defined then the HMC device is assigned to the "misc" class devices.37 *38#define HMCDRV_DEV_CLASS "hmcftp"39 */40 41#define HMCDRV_DEV_NAME "hmcdrv"42#define HMCDRV_DEV_BUSY_DELAY 500 /* delay between -EBUSY trials in ms */43#define HMCDRV_DEV_BUSY_RETRIES 3 /* number of retries on -EBUSY */44 45struct hmcdrv_dev_node {46 47#ifdef HMCDRV_DEV_CLASS48 struct cdev dev; /* character device structure */49 umode_t mode; /* mode of device node (unused, zero) */50#else51 struct miscdevice dev; /* "misc" device structure */52#endif53 54};55 56static int hmcdrv_dev_open(struct inode *inode, struct file *fp);57static int hmcdrv_dev_release(struct inode *inode, struct file *fp);58static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence);59static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,60 size_t len, loff_t *pos);61static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,62 size_t len, loff_t *pos);63static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,64 char __user *buf, size_t len);65 66/*67 * device operations68 */69static const struct file_operations hmcdrv_dev_fops = {70 .open = hmcdrv_dev_open,71 .llseek = hmcdrv_dev_seek,72 .release = hmcdrv_dev_release,73 .read = hmcdrv_dev_read,74 .write = hmcdrv_dev_write,75};76 77static struct hmcdrv_dev_node hmcdrv_dev; /* HMC device struct (static) */78 79#ifdef HMCDRV_DEV_CLASS80 81static struct class *hmcdrv_dev_class; /* device class pointer */82static dev_t hmcdrv_dev_no; /* device number (major/minor) */83 84/**85 * hmcdrv_dev_name() - provides a naming hint for a device node in /dev86 * @dev: device for which the naming/mode hint is87 * @mode: file mode for device node created in /dev88 *89 * See: devtmpfs.c, function devtmpfs_create_node()90 *91 * Return: recommended device file name in /dev92 */93static char *hmcdrv_dev_name(const struct device *dev, umode_t *mode)94{95 char *nodename = NULL;96 const char *devname = dev_name(dev); /* kernel device name */97 98 if (devname)99 nodename = kasprintf(GFP_KERNEL, "%s", devname);100 101 /* on device destroy (rmmod) the mode pointer may be NULL102 */103 if (mode)104 *mode = hmcdrv_dev.mode;105 106 return nodename;107}108 109#endif /* HMCDRV_DEV_CLASS */110 111/*112 * open()113 */114static int hmcdrv_dev_open(struct inode *inode, struct file *fp)115{116 int rc;117 118 /* check for non-blocking access, which is really unsupported119 */120 if (fp->f_flags & O_NONBLOCK)121 return -EINVAL;122 123 /* Because it makes no sense to open this device read-only (then a124 * FTP command cannot be emitted), we respond with an error.125 */126 if ((fp->f_flags & O_ACCMODE) == O_RDONLY)127 return -EINVAL;128 129 /* prevent unloading this module as long as anyone holds the130 * device file open - so increment the reference count here131 */132 if (!try_module_get(THIS_MODULE))133 return -ENODEV;134 135 fp->private_data = NULL; /* no command yet */136 rc = hmcdrv_ftp_startup();137 if (rc)138 module_put(THIS_MODULE);139 140 pr_debug("open file '/dev/%pD' with return code %d\n", fp, rc);141 return rc;142}143 144/*145 * release()146 */147static int hmcdrv_dev_release(struct inode *inode, struct file *fp)148{149 pr_debug("closing file '/dev/%pD'\n", fp);150 kfree(fp->private_data);151 fp->private_data = NULL;152 hmcdrv_ftp_shutdown();153 module_put(THIS_MODULE);154 return 0;155}156 157/*158 * lseek()159 */160static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence)161{162 switch (whence) {163 case SEEK_CUR: /* relative to current file position */164 pos += fp->f_pos; /* new position stored in 'pos' */165 break;166 167 case SEEK_SET: /* absolute (relative to beginning of file) */168 break; /* SEEK_SET */169 170 /* We use SEEK_END as a special indicator for a SEEK_SET171 * (set absolute position), combined with a FTP command172 * clear.173 */174 case SEEK_END:175 if (fp->private_data) {176 kfree(fp->private_data);177 fp->private_data = NULL;178 }179 180 break; /* SEEK_END */181 182 default: /* SEEK_DATA, SEEK_HOLE: unsupported */183 return -EINVAL;184 }185 186 if (pos < 0)187 return -EINVAL;188 189 fp->f_pos = pos;190 return pos;191}192 193/*194 * transfer (helper function)195 */196static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,197 char __user *buf, size_t len)198{199 ssize_t retlen;200 unsigned trials = HMCDRV_DEV_BUSY_RETRIES;201 202 do {203 retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);204 205 if (retlen != -EBUSY)206 break;207 208 msleep(HMCDRV_DEV_BUSY_DELAY);209 210 } while (--trials > 0);211 212 return retlen;213}214 215/*216 * read()217 */218static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,219 size_t len, loff_t *pos)220{221 ssize_t retlen;222 223 if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||224 (fp->private_data == NULL)) { /* no FTP cmd defined ? */225 return -EBADF;226 }227 228 retlen = hmcdrv_dev_transfer((char *) fp->private_data,229 *pos, ubuf, len);230 231 pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n",232 fp, (long long) *pos, retlen, len);233 234 if (retlen > 0)235 *pos += retlen;236 237 return retlen;238}239 240/*241 * write()242 */243static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,244 size_t len, loff_t *pos)245{246 ssize_t retlen;247 248 pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n",249 fp, (long long) *pos, len);250 251 if (!fp->private_data) { /* first expect a cmd write */252 fp->private_data = kmalloc(len + 1, GFP_KERNEL);253 254 if (!fp->private_data)255 return -ENOMEM;256 257 if (!copy_from_user(fp->private_data, ubuf, len)) {258 ((char *)fp->private_data)[len] = '\0';259 return len;260 }261 262 kfree(fp->private_data);263 fp->private_data = NULL;264 return -EFAULT;265 }266 267 retlen = hmcdrv_dev_transfer((char *) fp->private_data,268 *pos, (char __user *) ubuf, len);269 if (retlen > 0)270 *pos += retlen;271 272 pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen);273 274 return retlen;275}276 277/**278 * hmcdrv_dev_init() - creates a HMC drive CD/DVD device279 *280 * This function creates a HMC drive CD/DVD kernel device and an associated281 * device under /dev, using a dynamically allocated major number.282 *283 * Return: 0 on success, else an error code.284 */285int hmcdrv_dev_init(void)286{287 int rc;288 289#ifdef HMCDRV_DEV_CLASS290 struct device *dev;291 292 rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);293 294 if (rc)295 goto out_err;296 297 cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);298 hmcdrv_dev.dev.owner = THIS_MODULE;299 rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);300 301 if (rc)302 goto out_unreg;303 304 /* At this point the character device exists in the kernel (see305 * /proc/devices), but not under /dev nor /sys/devices/virtual. So306 * we have to create an associated class (see /sys/class).307 */308 hmcdrv_dev_class = class_create(HMCDRV_DEV_CLASS);309 310 if (IS_ERR(hmcdrv_dev_class)) {311 rc = PTR_ERR(hmcdrv_dev_class);312 goto out_devdel;313 }314 315 /* Finally a device node in /dev has to be established (as 'mkdev'316 * does from the command line). Notice that assignment of a device317 * node name/mode function is optional (only for mode != 0600).318 */319 hmcdrv_dev.mode = 0; /* "unset" */320 hmcdrv_dev_class->devnode = hmcdrv_dev_name;321 322 dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,323 "%s", HMCDRV_DEV_NAME);324 if (!IS_ERR(dev))325 return 0;326 327 rc = PTR_ERR(dev);328 class_destroy(hmcdrv_dev_class);329 hmcdrv_dev_class = NULL;330 331out_devdel:332 cdev_del(&hmcdrv_dev.dev);333 334out_unreg:335 unregister_chrdev_region(hmcdrv_dev_no, 1);336 337out_err:338 339#else /* !HMCDRV_DEV_CLASS */340 hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;341 hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;342 hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;343 hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */344 rc = misc_register(&hmcdrv_dev.dev);345#endif /* HMCDRV_DEV_CLASS */346 347 return rc;348}349 350/**351 * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device352 */353void hmcdrv_dev_exit(void)354{355#ifdef HMCDRV_DEV_CLASS356 if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {357 device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);358 class_destroy(hmcdrv_dev_class);359 }360 361 cdev_del(&hmcdrv_dev.dev);362 unregister_chrdev_region(hmcdrv_dev_no, 1);363#else /* !HMCDRV_DEV_CLASS */364 misc_deregister(&hmcdrv_dev.dev);365#endif /* HMCDRV_DEV_CLASS */366}367