/*======================================================================
  
    This driver provides a method to access memory not used by the kernel
    itself (i.e. if the kernel commandline mem=xxx is used). To actually
    use slram at least mtdblock or mtdchar is required (for block or
    character device access).
  
    Usage:
  
    if compiled as loadable module:
      modprobe slram map=<name>,<start>,<end/offset>
    if statically linked into the kernel use the following kernel cmd.line
      slram=<name>,<start>,<end/offset>
  
    <name>: name of the device that will be listed in /proc/mtd
    <start>: start of the memory region, decimal or hex (0xabcdef)
    <end/offset>: end of the memory region. It's possible to use +0x1234
                  to specify the offset instead of the absolute address
  
    NOTE:
    With slram it's only possible to map a contiguous memory region. Therefore
    if there's a device mapped somewhere in the region specified slram will
    fail to load (see kernel log if modprobe fails).
  
    -
  
    Jochen Schaeuble <psionic@psionic.de>
  
  ======================================================================*/
  
  
  #include <linux/module.h>
  #include <asm/uaccess.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/ptrace.h>
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/timer.h>
  #include <linux/major.h>
  #include <linux/fs.h>
  #include <linux/ioctl.h>
  #include <linux/init.h>
  #include <linux/io.h>
  
  #include <linux/mtd/mtd.h>
  
  #define SLRAM_MAX_DEVICES_PARAMS 6		/* 3 parameters / device */
  #define SLRAM_BLK_SZ 0x4000
  
  #define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)
  #define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)
  
  typedef struct slram_priv {
  	u_char *start;
  	u_char *end;
  } slram_priv_t;
  
  typedef struct slram_mtd_list {
  	struct mtd_info *mtdinfo;
  	struct slram_mtd_list *next;
  } slram_mtd_list_t;
  
  #ifdef MODULE
  static char *map[SLRAM_MAX_DEVICES_PARAMS];
  
  module_param_array(map, charp, NULL, 0);
  MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
  #else
  static char *map;
  #endif
  
  static slram_mtd_list_t *slram_mtdlist = NULL;
  
  static int slram_erase(struct mtd_info *, struct erase_info *);
  static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
  		resource_size_t *);
  static int slram_unpoint(struct mtd_info *, loff_t, size_t);
  static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
  static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
  
  static int slram_erase(struct mtd_info *mtd, struct erase_info *instr)
  {
  	slram_priv_t *priv = mtd->priv;
  
  	memset(priv->start + instr->addr, 0xff, instr->len);
  	/* This'll catch a few races. Free the thing before returning :)
  	 * I don't feel at all ashamed. This kind of thing is possible anyway
  	 * with flash, but unlikely.
  	 */
  	instr->state = MTD_ERASE_DONE;
  	mtd_erase_callback(instr);
  	return(0);
  }
  
  static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
  		size_t *retlen, void **virt, resource_size_t *phys)
  {
  	slram_priv_t *priv = mtd->priv;
  
  	*virt = priv->start + from;
  	*retlen = len;
  	return(0);
  }
  
  static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
  {
  	return 0;
  }
  
  static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
  		size_t *retlen, u_char *buf)
  {
  	slram_priv_t *priv = mtd->priv;
  
  	memcpy(buf, priv->start + from, len);
  	*retlen = len;
  	return(0);
  }
  
  static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
  		size_t *retlen, const u_char *buf)
  {
  	slram_priv_t *priv = mtd->priv;
  
  	memcpy(priv->start + to, buf, len);
  	*retlen = len;
  	return(0);
  }
  
  /*====================================================================*/
  
  static int register_device(char *name, unsigned long start, unsigned long length)
  {
  	slram_mtd_list_t **curmtd;
  
  	curmtd = &slram_mtdlist;
  	while (*curmtd) {
  		curmtd = &(*curmtd)->next;
  	}
  
  	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
  	if (!(*curmtd)) {
  		E("slram: Cannot allocate new MTD device.
  ");
  		return(-ENOMEM);
  	}
  	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
  	(*curmtd)->next = NULL;
  
  	if ((*curmtd)->mtdinfo)	{
  		(*curmtd)->mtdinfo->priv =
  			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
  
  		if (!(*curmtd)->mtdinfo->priv) {
  			kfree((*curmtd)->mtdinfo);
  			(*curmtd)->mtdinfo = NULL;
  		}
  	}
  
  	if (!(*curmtd)->mtdinfo) {
  		E("slram: Cannot allocate new MTD device.
  ");
  		return(-ENOMEM);
  	}
  
  	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
  				ioremap(start, length))) {
  		E("slram: ioremap failed
  ");
  		return -EIO;
  	}
  	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
  		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
  
  
  	(*curmtd)->mtdinfo->name = name;
  	(*curmtd)->mtdinfo->size = length;
  	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
  	(*curmtd)->mtdinfo->_erase = slram_erase;
  	(*curmtd)->mtdinfo->_point = slram_point;
  	(*curmtd)->mtdinfo->_unpoint = slram_unpoint;
  	(*curmtd)->mtdinfo->_read = slram_read;
  	(*curmtd)->mtdinfo->_write = slram_write;
  	(*curmtd)->mtdinfo->owner = THIS_MODULE;
  	(*curmtd)->mtdinfo->type = MTD_RAM;
  	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
  	(*curmtd)->mtdinfo->writesize = 1;
  
  	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
  		E("slram: Failed to register new device
  ");
  		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
  		kfree((*curmtd)->mtdinfo->priv);
  		kfree((*curmtd)->mtdinfo);
  		return(-EAGAIN);
  	}
  	T("slram: Registered device %s from %luKiB to %luKiB
  ", name,
  			(start / 1024), ((start + length) / 1024));
  	T("slram: Mapped from 0x%p to 0x%p
  ",
  			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
  			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
  	return(0);
  }
  
  static void unregister_devices(void)
  {
  	slram_mtd_list_t *nextitem;
  
  	while (slram_mtdlist) {
  		nextitem = slram_mtdlist->next;
  		mtd_device_unregister(slram_mtdlist->mtdinfo);
  		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
  		kfree(slram_mtdlist->mtdinfo->priv);
  		kfree(slram_mtdlist->mtdinfo);
  		kfree(slram_mtdlist);
  		slram_mtdlist = nextitem;
  	}
  }
  
  static unsigned long handle_unit(unsigned long value, char *unit)
  {
  	if ((*unit == 'M') || (*unit == 'm')) {
  		return(value * 1024 * 1024);
  	} else if ((*unit == 'K') || (*unit == 'k')) {
  		return(value * 1024);
  	}
  	return(value);
  }
  
  static int parse_cmdline(char *devname, char *szstart, char *szlength)
  {
  	char *buffer;
  	unsigned long devstart;
  	unsigned long devlength;
  
  	if ((!devname) || (!szstart) || (!szlength)) {
  		unregister_devices();
  		return(-EINVAL);
  	}
  
  	devstart = simple_strtoul(szstart, &buffer, 0);
  	devstart = handle_unit(devstart, buffer);
  
  	if (*(szlength) != '+') {
  		devlength = simple_strtoul(szlength, &buffer, 0);
  		devlength = handle_unit(devlength, buffer);
  		if (devlength < devstart)
  			goto err_out;
  
  		devlength -= devstart;
  	} else {
  		devlength = simple_strtoul(szlength + 1, &buffer, 0);
  		devlength = handle_unit(devlength, buffer);
  	}
  	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx
  ",
  			devname, devstart, devlength);
  	if (devlength % SLRAM_BLK_SZ != 0)
  		goto err_out;
  
  	if ((devstart = register_device(devname, devstart, devlength))){
  		unregister_devices();
  		return((int)devstart);
  	}
  	return(0);
  
  err_out:
  	E("slram: Illegal length parameter.
  ");
  	return(-EINVAL);
  }
  
  #ifndef MODULE
  
  static int __init mtd_slram_setup(char *str)
  {
  	map = str;
  	return(1);
  }
  
  __setup("slram=", mtd_slram_setup);
  
  #endif
  
  static int __init init_slram(void)
  {
  	char *devname;
  
  #ifndef MODULE
  	char *devstart;
  	char *devlength;
  
  	if (!map) {
  		E("slram: not enough parameters.
  ");
  		return(-EINVAL);
  	}
  	while (map) {
  		devname = devstart = devlength = NULL;
  
  		if (!(devname = strsep(&map, ","))) {
  			E("slram: No devicename specified.
  ");
  			break;
  		}
  		T("slram: devname = %s
  ", devname);
  		if ((!map) || (!(devstart = strsep(&map, ",")))) {
  			E("slram: No devicestart specified.
  ");
  		}
  		T("slram: devstart = %s
  ", devstart);
  		if ((!map) || (!(devlength = strsep(&map, ",")))) {
  			E("slram: No devicelength / -end specified.
  ");
  		}
  		T("slram: devlength = %s
  ", devlength);
  		if (parse_cmdline(devname, devstart, devlength) != 0) {
  			return(-EINVAL);
  		}
  	}
  #else
  	int count;
  	int i;
  
  	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
  			count++) {
  	}
  
  	if ((count % 3 != 0) || (count == 0)) {
  		E("slram: not enough parameters.
  ");
  		return(-EINVAL);
  	}
  	for (i = 0; i < (count / 3); i++) {
  		devname = map[i * 3];
  
  		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
  			return(-EINVAL);
  		}
  
  	}
  #endif /* !MODULE */
  
  	return(0);
  }
  
  static void __exit cleanup_slram(void)
  {
  	unregister_devices();
  }
  
  module_init(init_slram);
  module_exit(cleanup_slram);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
  MODULE_DESCRIPTION("MTD driver for uncached system RAM");