[MTD] slram driver cleanup

Add error checks to read/write functions and add an eraseblock size.
Makes slram a suitable device for JFFS2.

Signed-off-by: Josh Boyer <jdub@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/mtd/devices/slram.c

@@ -1,6 +1,6 @@
 /*======================================================================
 
-  $Id: slram.c,v 1.33 2005/01/05 18:05:13 dwmw2 Exp $
+  $Id: slram.c,v 1.34 2005/01/06 21:16:42 jwboyer Exp $
 
   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
@@ -50,6 +50,7 @@
 #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)
@@ -108,6 +109,9 @@ static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
 {
 	slram_priv_t *priv = mtd->priv;
 
+	if (from + len > mtd->size)
+		return -EINVAL;
+
 	*mtdbuf = priv->start + from;
 	*retlen = len;
 	return(0);
@@ -121,7 +125,13 @@ 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;
-
+
+	if (from > mtd->size)
+		return -EINVAL;
+
+	if (from + len > mtd->size)
+		len = mtd->size - from;
+
 	memcpy(buf, priv->start + from, len);
 
 	*retlen = len;
@@ -133,6 +143,9 @@ static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
 {
 	slram_priv_t *priv = mtd->priv;
 
+	if (to + len > mtd->size)
+		return -EINVAL;
+
 	memcpy(priv->start + to, buf, len);
 
 	*retlen = len;
@@ -188,15 +201,15 @@ static int register_device(char *name, unsigned long start, unsigned long length
 	(*curmtd)->mtdinfo->name = name;
 	(*curmtd)->mtdinfo->size = length;
 	(*curmtd)->mtdinfo->flags = MTD_CLEAR_BITS | MTD_SET_BITS |
-					MTD_WRITEB_WRITEABLE | MTD_VOLATILE;
+					MTD_WRITEB_WRITEABLE | MTD_VOLATILE | 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 = 0x0;
+	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
 
 	if (add_mtd_device((*curmtd)->mtdinfo))	{
 		E("slram: Failed to register new device\n");
@@ -261,7 +274,7 @@ static int parse_cmdline(char *devname, char *szstart, char *szlength)
 	}
 	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
 			devname, devstart, devlength);
-	if ((devstart < 0) || (devlength < 0)) {
+	if ((devstart < 0) || (devlength < 0) || (devlength % SLRAM_BLK_SZ != 0)) {
 		E("slram: Illegal start / length parameter.\n");
 		return(-EINVAL);
 	}