sos-code-article10/sos/chardev.c

/* Copyright (C) 2005      David Decotigny

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
   USA.
*/

#include <sos/assert.h>
#include <sos/types.h>
#include <sos/fs.h>
#include <sos/list.h>
#include <sos/kmalloc.h>

#include "chardev.h"

struct sos_chardev_class
{
  sos_ui32_t                device_class;
  struct sos_chardev_ops   *ops;

  /** This corresponds to the chardev_class_custom_data field passed
      to open/read/etc. and to sos_chardev_register_class() */
  void                     *custom_data;

  sos_count_t               ref_cnt; /**< increased each time a FS
					  node is opened */

  struct sos_chardev_class *next, *prev;
};


struct sos_chardev_opened_file
{
  /** "normal" VFS opened file structure is available in this
      structure */
  struct sos_fs_opened_file  super;

  /** Additional information for this opened file: the device's class
      structure */
  struct sos_chardev_class  *class;
};


/** The list of registered classes, ie the dictionary major number ->
    device class description */
static struct sos_chardev_class *registered_chardev_classes;


/* Forward declarations */
static struct sos_fs_ops_opened_file chardev_ops_opened_file;
static struct sos_fs_ops_opened_chardev chardev_ops_opened_chardev;

static sos_ret_t
chardev_helper_new_opened_file(struct sos_fs_node * this,
			       const struct sos_process * owner,
			       sos_ui32_t open_flags,
			       struct sos_fs_opened_file ** result_of);
static sos_ret_t
chardev_helper_close_opened_file(struct sos_fs_node * this,
				 struct sos_fs_opened_file * of);
static sos_ret_t
duplicate_opened_chardev(struct sos_fs_opened_file *this,
			 const struct sos_process  * for_owner,
			 struct sos_fs_opened_file **result);


/**
 * Return the device descriptionn structure for the corresponding
 * device class, or NULL when none found.
 */
static struct sos_chardev_class * lookup_chardev_class(sos_ui32_t device_class)
{
  struct sos_chardev_class *chardev;
  int nb;

  list_foreach (registered_chardev_classes, chardev, nb)
    {
      if (chardev->device_class == device_class)
	return chardev;
    }

  return NULL;
}


sos_ret_t sos_chardev_register_class (sos_ui32_t device_class,
				      struct sos_chardev_ops *ops,
				      void * chardev_class_custom_data)
{
  struct sos_chardev_class *chardev;

  /* Make sure this device class is not already registered */
  chardev = lookup_chardev_class(device_class);
  if (NULL != chardev)
    return -SOS_EBUSY;

  /* Allocate and initialize a new device description */
  chardev = (struct sos_chardev_class *)
    sos_kmalloc(sizeof(struct sos_chardev_class), 0);
  if (chardev == NULL)
    return -SOS_ENOMEM;

  chardev->device_class = device_class;
  chardev->custom_data  = chardev_class_custom_data;
  chardev->ops          = ops;
  chardev->ref_cnt      = 1;

  /* insert it into the list */
  list_add_tail (registered_chardev_classes, chardev);

  return SOS_OK;
}


sos_ret_t sos_chardev_unregister_class (sos_ui32_t device_class)
{
  struct sos_chardev_class *chardev;

  /* Make sure this device class is already registered */
  chardev = lookup_chardev_class(device_class);
  if (NULL == chardev)
    return -SOS_ENODEV;

  /* Make sure no files are already opened for it */
  if (chardev->ref_cnt != 1)
    return -SOS_EBUSY;

  /* remove it from the list */
  list_delete (registered_chardev_classes, chardev);
  return sos_kfree((sos_vaddr_t)chardev);
}



sos_ret_t sos_chardev_helper_ref_new_fsnode(struct sos_fs_node * this)
{
  this->new_opened_file   = chardev_helper_new_opened_file;
  this->close_opened_file = chardev_helper_close_opened_file;

  return SOS_OK;
}


sos_ret_t sos_chardev_helper_release_fsnode(struct sos_fs_node * this)
{
  return SOS_OK;
}


/** Callback called each time an FS-node is opened by a user process:
    create a new sos_chardev_opened_file object associated to the
    correct major number, and call the device driver's open method */
static sos_ret_t
chardev_helper_new_opened_file(struct sos_fs_node * this,
			       const struct sos_process * owner,
			       sos_ui32_t open_flags,
			       struct sos_fs_opened_file ** result_of)
{
  sos_ret_t retval;
  struct sos_chardev_opened_file *chardev_of;

  /* Lookup the character device description structure */
  struct sos_chardev_class * chardev
    = lookup_chardev_class(this->dev_id.device_class);
  if (NULL == chardev)
    return -SOS_ENODEV;

  /* Alloocate the new "open file" description structure */
  chardev_of = (struct sos_chardev_opened_file*)
    sos_kmalloc(sizeof(struct sos_chardev_opened_file), 0);
  if (NULL == chardev_of)
    return -SOS_ENOMEM;

  memset(chardev_of, 0x0, sizeof(struct sos_chardev_opened_file));
  chardev_of->class = chardev;
  *result_of = & chardev_of->super;

  /* Increase the reference coount for that node */
  SOS_ASSERT_FATAL(chardev->ref_cnt >= 1);
  chardev->ref_cnt ++;

  /* Initialize the read/write/seek callbacks */
  (*result_of)->owner       = owner;
  (*result_of)->open_flags  = open_flags;
  (*result_of)->ops_file    = & chardev_ops_opened_file;
  (*result_of)->ops_chardev = & chardev_ops_opened_chardev;

  /* Call the open callback */
  retval = chardev->ops->open(this, & chardev_of->super, chardev->custom_data);
  if (SOS_OK != retval)
    {
      sos_kfree((sos_vaddr_t) chardev_of);
      chardev->ref_cnt --;
      *result_of = NULL;
      return retval;
    }

  /* Specify the duplicate method */
  (*result_of)->duplicate = duplicate_opened_chardev;

  return retval;
}


/** Callback called each time an opened file is closed. Un-allocate
    the associated sos_chardev_opened_file object */
static sos_ret_t
chardev_helper_close_opened_file(struct sos_fs_node * this,
				 struct sos_fs_opened_file * of)
{
  sos_ret_t retval;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)of);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);

  /* Free the new "open file" description structure */
  if (NULL != chardev->ops->close)
    retval = chardev->ops->close(& chardev_of->super, chardev->custom_data);
  else
    retval = SOS_OK;
  if (SOS_OK != retval)
    return retval;

  /* Decrease the reference coount for that node */
  SOS_ASSERT_FATAL(chardev->ref_cnt > 1);
  chardev->ref_cnt --;
  
  sos_kfree((sos_vaddr_t) chardev_of);
  return retval;
}


/**
 * Callback called each time a process is "forked": create a new
 * sos_chardev_opened_file for the new process.
 *
 * @note Almost identical to the open callback.
 */
static sos_ret_t
duplicate_opened_chardev(struct sos_fs_opened_file *this,
			 const struct sos_process  * for_owner,
			 struct sos_fs_opened_file **result)
{
  sos_ret_t retval;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);
  struct sos_chardev_opened_file *new_chardev_of;
  struct sos_fs_node * fsnode = sos_fs_nscache_get_fs_node(this->direntry);

  *result = NULL;

  /* Lookup the character device description structure */
  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);

  /* Allocate a new duplicate copy of the original opened file */
  new_chardev_of = (struct sos_chardev_opened_file*)
    sos_kmalloc(sizeof(struct sos_chardev_opened_file), 0);
  if (NULL == new_chardev_of)
    return -SOS_ENOMEM;

  memcpy(new_chardev_of, chardev_of, sizeof(*new_chardev_of));
  new_chardev_of->super.owner    = for_owner;
  new_chardev_of->super.direntry = NULL; /* Reset the direntry
					    for the new opened file */
  SOS_ASSERT_FATAL(chardev->ref_cnt > 1);
  chardev->ref_cnt ++;

  retval = chardev->ops->open(fsnode,
			      & new_chardev_of->super, chardev->custom_data);
  if (SOS_OK != retval)
    {
      sos_kfree((sos_vaddr_t) new_chardev_of);
      chardev->ref_cnt --;
      return retval;
    }

  /* Make sure the required methods are overloaded */
  SOS_ASSERT_FATAL(NULL != new_chardev_of->super.ops_file);
  SOS_ASSERT_FATAL(NULL != new_chardev_of->super.ops_file->seek);
  SOS_ASSERT_FATAL(NULL != new_chardev_of->super.ops_file->read);

  *result = & new_chardev_of->super;
  return retval;
}


/*
 * FS generic character device wrapper functions
 */

/**
 * Callback called to change the position in the opened file: call the
 * seek method of the device driver.
 */
static sos_ret_t chardev_wrap_seek(struct sos_fs_opened_file *this,
				   sos_lsoffset_t offset,
				   sos_seek_whence_t whence,
				   /* out */ sos_lsoffset_t * result_position)
{
  sos_ret_t retval = -SOS_ENOSYS;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);
  SOS_ASSERT_FATAL(NULL != chardev->ops);

  if (NULL != chardev->ops->seek)
    retval = chardev->ops->seek(this, offset, whence, result_position);
  
  return retval;
}


/**
 * Callback called to read the contents of the opened file: call the
 * read method of the device driver.
 */
static sos_ret_t chardev_wrap_read(struct sos_fs_opened_file *this,
				   sos_uaddr_t dest_buf,
				   sos_size_t * /* in/out */len)
{
  sos_ret_t retval = -SOS_ENOSYS;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);
  SOS_ASSERT_FATAL(NULL != chardev->ops);

  if (NULL != chardev->ops->read)
    retval = chardev->ops->read(this, dest_buf, len);
  
  return retval;
}


/**
 * Callback called to write bytes to the opened file: call the write
 * method of the device driver.
 */
static sos_ret_t chardev_wrap_write(struct sos_fs_opened_file *this,
				    sos_uaddr_t src_buf,
				    sos_size_t * /* in/out */len)
{
  sos_ret_t retval = -SOS_ENOSYS;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);
  SOS_ASSERT_FATAL(NULL != chardev->ops);

  if (NULL != chardev->ops->write)
    retval = chardev->ops->write(this, src_buf, len);
  
  return retval;
}


/**
 * Callback called to map the contents of the opened file: call the
 * map method of the device driver.
 */
static sos_ret_t chardev_wrap_mmap(struct sos_fs_opened_file *this,
				   sos_uaddr_t *uaddr, sos_size_t size,
				   sos_ui32_t access_rights,
				   sos_ui32_t flags,
				   sos_luoffset_t offset)
{
  sos_ret_t retval = -SOS_ENOSYS;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);
  SOS_ASSERT_FATAL(NULL != chardev->ops);

  if (NULL != chardev->ops->mmap)
    retval = chardev->ops->mmap(this, uaddr, size,
				access_rights, flags, offset);
  
  return retval;
}


/**
 * Callback called to change the state of the opened file: call the
 * fcntl method of the device driver.
 */
static sos_ret_t chardev_wrap_fcntl(struct sos_fs_opened_file *this,
				    int req_id,
				    sos_ui32_t req_arg)
{
  sos_ret_t retval = -SOS_ENOSYS;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);
  SOS_ASSERT_FATAL(NULL != chardev->ops);

  if (NULL != chardev->ops->fcntl)
    retval = chardev->ops->fcntl(this, req_id, req_arg);
  
  return retval;
}


/**
 * Callback called to control the underlying device: call the ioctl
 * method of the device driver.
 */
static sos_ret_t chardev_wrap_ioctl(struct sos_fs_opened_file *this,
				    int req_id,
				    sos_ui32_t req_arg)
{
  sos_ret_t retval = -SOS_ENOSYS;
  struct sos_chardev_opened_file *chardev_of
    = ((struct sos_chardev_opened_file*)this);

  struct sos_chardev_class * chardev = chardev_of->class;
  SOS_ASSERT_FATAL(NULL != chardev);
  SOS_ASSERT_FATAL(NULL != chardev->ops);

  if (NULL != chardev->ops->ioctl)
    retval = chardev->ops->ioctl(this, req_id, req_arg);
  
  return retval;
}


/**
 * Gather the callbacks for a "character device" opened file
 */
static struct sos_fs_ops_opened_file chardev_ops_opened_file
  = (struct sos_fs_ops_opened_file) {
    .seek  = chardev_wrap_seek,
    .read  = chardev_wrap_read,
    .write = chardev_wrap_write,
    .mmap  = chardev_wrap_mmap,
    .fcntl = chardev_wrap_fcntl
  };


static struct sos_fs_ops_opened_chardev chardev_ops_opened_chardev
  = (struct sos_fs_ops_opened_chardev) {
    .ioctl = chardev_wrap_ioctl
  };