ldd ——scull(main.c).txt

详细介绍的scull字符设备驱动程序的实现！

339                 loff_t *f_pos)
340 {
341         struct scull_dev *dev = filp->private_data;
342         struct scull_qset *dptr;
343         int quantum = dev->quantum, qset = dev->qset;
344         int itemsize = quantum * qset;
345         int item, s_pos, q_pos, rest;
346         ssize_t retval = -ENOMEM; /* value used in "goto out" statements */
347 
348         if (down_interruptible(&dev->sem))
349                 return -ERESTARTSYS;
350 
351         /* find listitem, qset index and offset in the quantum */
352         item = (long)*f_pos / itemsize;
353         rest = (long)*f_pos % itemsize;
354         s_pos = rest / quantum; q_pos = rest % quantum;
355 
356         /* follow the list up to the right position */
357         dptr = scull_follow(dev, item);
358         if (dptr == NULL)
359                 goto out;
360         if (!dptr->data) {
361                 dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);
362                 if (!dptr->data)
363                         goto out;
364                 memset(dptr->data, 0, qset * sizeof(char *));
365         }
366         if (!dptr->data[s_pos]) {
367                 dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
368                 if (!dptr->data[s_pos])
369                         goto out;
370         }
371         /* write only up to the end of this quantum */
372         if (count > quantum - q_pos)
373                 count = quantum - q_pos;
374 
375         if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) {
376                 retval = -EFAULT;
377                 goto out;
378         }
379         *f_pos += count;
380         retval = count;
381 
382         /* update the size */
383         if (dev->size < *f_pos)
384                 dev->size = *f_pos;
385 
386   out:
387         up(&dev->sem);
388         return retval;
389 }
390 
391 /*
392  * The ioctl() implementation
393  */
394 
395 int scull_ioctl(struct inode *inode, struct file *filp,
396                  unsigned int cmd, unsigned long arg)
397 {
398 
399         int err = 0, tmp;
400         int retval = 0;
401     
402         /*
403          * extract the type and number bitfields, and don't decode
404          * wrong cmds: return ENOTTY (inappropriate ioctl) before access_ok()
405          */
406         if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY;
407         if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY;
408 
409         /*
410          * the direction is a bitmask, and VERIFY_WRITE catches R/W
411          * transfers. `Type' is user-oriented, while
412          * access_ok is kernel-oriented, so the concept of "read" and
413          * "write" is reversed
414          */
415         if (_IOC_DIR(cmd) & _IOC_READ)
416                 err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
417         else if (_IOC_DIR(cmd) & _IOC_WRITE)
418                 err =  !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
419         if (err) return -EFAULT;
420 
421         switch(cmd) {
422 
423           case SCULL_IOCRESET:
424                 scull_quantum = SCULL_QUANTUM;
425                 scull_qset = SCULL_QSET;
426                 break;
427         
428           case SCULL_IOCSQUANTUM: /* Set: arg points to the value */
429                 if (! capable (CAP_SYS_ADMIN))
430                         return -EPERM;
431                 retval = __get_user(scull_quantum, (int __user *)arg);
432                 break;
433 
434           case SCULL_IOCTQUANTUM: /* Tell: arg is the value */
435                 if (! capable (CAP_SYS_ADMIN))
436                         return -EPERM;
437                 scull_quantum = arg;
438                 break;
439 
440           case SCULL_IOCGQUANTUM: /* Get: arg is pointer to result */
441                 retval = __put_user(scull_quantum, (int __user *)arg);
442                 break;
443 
444           case SCULL_IOCQQUANTUM: /* Query: return it (it's positive) */
445                 return scull_quantum;
446 
447           case SCULL_IOCXQUANTUM: /* eXchange: use arg as pointer */
448                 if (! capable (CAP_SYS_ADMIN))
449                         return -EPERM;
450                 tmp = scull_quantum;
451                 retval = __get_user(scull_quantum, (int __user *)arg);
452                 if (retval == 0)
453                         retval = __put_user(tmp, (int __user *)arg);
454                 break;
455 
456           case SCULL_IOCHQUANTUM: /* sHift: like Tell + Query */
457                 if (! capable (CAP_SYS_ADMIN))
458                         return -EPERM;
459                 tmp = scull_quantum;
460                 scull_quantum = arg;
461                 return tmp;
462         
463           case SCULL_IOCSQSET:
464                 if (! capable (CAP_SYS_ADMIN))
465                         return -EPERM;
466                 retval = __get_user(scull_qset, (int __user *)arg);
467                 break;
468 
469           case SCULL_IOCTQSET:
470                 if (! capable (CAP_SYS_ADMIN))
471                         return -EPERM;
472                 scull_qset = arg;
473                 break;
474 
475           case SCULL_IOCGQSET:
476                 retval = __put_user(scull_qset, (int __user *)arg);
477                 break;
478 
479           case SCULL_IOCQQSET:
480                 return scull_qset;
481 
482           case SCULL_IOCXQSET:
483                 if (! capable (CAP_SYS_ADMIN))
484                         return -EPERM;
485                 tmp = scull_qset;
486                 retval = __get_user(scull_qset, (int __user *)arg);
487                 if (retval == 0)
488                         retval = put_user(tmp, (int __user *)arg);
489                 break;
490 
491           case SCULL_IOCHQSET:
492                 if (! capable (CAP_SYS_ADMIN))
493                         return -EPERM;
494                 tmp = scull_qset;
495                 scull_qset = arg;
496                 return tmp;
497 
498         /*
499          * The following two change the buffer size for scullpipe.
500          * The scullpipe device uses this same ioctl method, just to
501          * write less code. Actually, it's the same driver, isn't it?
502          */
503 
504           case SCULL_P_IOCTSIZE:
505                 scull_p_buffer = arg;
506                 break;
507 
508           case SCULL_P_IOCQSIZE:
509                 return scull_p_buffer;
510 
511 
512           default:  /* redundant, as cmd was checked against MAXNR */
513                 return -ENOTTY;
514         }
515         return retval;
516 
517 }
518 
519 
520 
521 /*
522  * The "extended" operations -- only seek
523  */
524 
525 loff_t scull_llseek(struct file *filp, loff_t off, int whence)
526 {
527         struct scull_dev *dev = filp->private_data;
528         loff_t newpos;
529 
530         switch(whence) {
531           case 0: /* SEEK_SET */
532                 newpos = off;
533                 break;
534 
535           case 1: /* SEEK_CUR */
536                 newpos = filp->f_pos + off;
537                 break;
538 
539           case 2: /* SEEK_END */
540                 newpos = dev->size + off;
541                 break;
542 
543           default: /* can't happen */
544                 return -EINVAL;
545         }
546         if (newpos < 0) return -EINVAL;
547         filp->f_pos = newpos;
548         return newpos;
549 }
550 
551 
552 
553 struct file_operations scull_fops = {
554         .owner =    THIS_MODULE,
555         .llseek =   scull_llseek,
556         .read =     scull_read,
557         .write =    scull_write,
558         .ioctl =    scull_ioctl,
559         .open =     scull_open,
560         .release =  scull_release,
561 };
562 
563 /*
564  * Finally, the module stuff
565  */
566 
567 /*
568  * The cleanup function is used to handle initialization failures as well.
569  * Thefore, it must be careful to work correctly even if some of the items
570  * have not been initialized
571  */
572 void scull_cleanup_module(void)
573 {
574         int i;
575         dev_t devno = MKDEV(scull_major, scull_minor);
576 
577         /* Get rid of our char dev entries */
578         if (scull_devices) {
579                 for (i = 0; i < scull_nr_devs; i++) {
580                         scull_trim(scull_devices + i);
581                         cdev_del(&scull_devices[i].cdev);
582                 }
583                 kfree(scull_devices);
584         }
585 
586 #ifdef SCULL_DEBUG /* use proc only if debugging */
587         scull_remove_proc();
588 #endif
589 
590         /* cleanup_module is never called if registering failed */
591         unregister_chrdev_region(devno, scull_nr_devs);
592 
593         /* and call the cleanup functions for friend devices */
594         scull_p_cleanup();
595         scull_access_cleanup();
596 
597 }
598 
599 
600 /*
601  * Set up the char_dev structure for this device.
602  */
603 static void scull_setup_cdev(struct scull_dev *dev, int index)
604 {
605         int err, devno = MKDEV(scull_major, scull_minor + index);
606     
607         cdev_init(&dev->cdev, &scull_fops);
608         dev->cdev.owner = THIS_MODULE;
609         dev->cdev.ops = &scull_fops;
610         err = cdev_add (&dev->cdev, devno, 1);
611         /* Fail gracefully if need be */
612         if (err)
613                 printk(KERN_NOTICE "Error %d adding scull%d", err, index);
614 }
615 
616 
617 int scull_init_module(void)
618 {
619         int result, i;
620         dev_t dev = 0;
621 
622 /*
623  * Get a range of minor numbers to work with, asking for a dynamic
624  * major unless directed otherwise at load time.
625  */
626         if (scull_major) {
627                 dev = MKDEV(scull_major, scull_minor);
628                 result = register_chrdev_region(dev, scull_nr_devs, "scull");
629         } else {
630                 result = alloc_chrdev_region(&dev, scull_minor, scull_nr_devs,
631                                 "scull");
632                 scull_major = MAJOR(dev);
633         }
634         if (result < 0) {
635                 printk(KERN_WARNING "scull: can't get major %d\n", scull_major);
636                 return result;
637         }
638 
639         /* 
640          * allocate the devices -- we can't have them static, as the number
641          * can be specified at load time
642          */
643         scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);
644         if (!scull_devices) {
645                 result = -ENOMEM;
646                 goto fail;  /* Make this more graceful */
647         }
648         memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));
649 
650         /* Initialize each device. */
651         for (i = 0; i < scull_nr_devs; i++) {
652                 scull_devices[i].quantum = scull_quantum;
653                 scull_devices[i].qset = scull_qset;
654                 init_MUTEX(&scull_devices[i].sem);
655                 scull_setup_cdev(&scull_devices[i], i);
656         }
657 
658         /* At this point call the init function for any friend device */
659         dev = MKDEV(scull_major, scull_minor + scull_nr_devs);
660         dev += scull_p_init(dev);
661         dev += scull_access_init(dev);
662 
663 #ifdef SCULL_DEBUG /* only when debugging */
664         scull_create_proc();
665 #endif
666 
667         return 0; /* succeed */
668 
669   fail:
670         scull_cleanup_module();
671         return result;
672 }
673 
674 module_init(scull_init_module);
675 module_exit(scull_cleanup_module);
676