fbdev: hecubafb bugfix

This patch is a bugfix for hecubafb_write which would return an incorrect
error value for the bytecount from framebuffer writes.

Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 25 deletions

diff --git a/drivers/video/hecubafb.c b/drivers/video/hecubafb.c
index 94e0df8a6f60..b77d033665da 100644
--- a/drivers/video/hecubafb.c
+++ b/drivers/video/hecubafb.c
@@ -270,41 +270,43 @@ static void hecubafb_imageblit(struct fb_info *info,
 static ssize_t hecubafb_write(struct fb_info *info, const char __user *buf,
                                 size_t count, loff_t *ppos)
 {
-        unsigned long p;
-        int err=-EINVAL;
-        struct hecubafb_par *par;
-        unsigned int xres;
-        unsigned int fbmemlength;
+        struct hecubafb_par *par = info->par;
+        unsigned long p = *ppos;
+        void *dst;
+        int err = 0;
+        unsigned long total_size;
 
-        p = *ppos;
-        par = info->par;
-        xres = info->var.xres;
-        fbmemlength = (xres * info->var.yres)/8;
+        if (info->state != FBINFO_STATE_RUNNING)
+                return -EPERM;
 
-        if (p > fbmemlength)
-                return -ENOSPC;
+        total_size = info->fix.smem_len;
 
-        err = 0;
-        if ((count + p) > fbmemlength) {
-                count = fbmemlength - p;
-                err = -ENOSPC;
+        if (p > total_size)
+                return -EFBIG;
+
+        if (count > total_size) {
+                err = -EFBIG;
+                count = total_size;
         }
 
-        if (count) {
-                char *base_addr;
+        if (count + p > total_size) {
+                if (!err)
+                        err = -ENOSPC;
 
-                base_addr = (char __force *)info->screen_base;
-                count -= copy_from_user(base_addr + p, buf, count);
-                *ppos += count;
-                err = -EFAULT;
+                count = total_size - p;
         }
 
-        hecubafb_dpy_update(par);
+        dst = (void __force *) (info->screen_base + p);
+
+        if (copy_from_user(dst, buf, count))
+                err = -EFAULT;
 
-        if (count)
-                return count;
+        if  (!err)
+                *ppos += count;
+
+        hecubafb_dpy_update(par);
 
-        return err;
+        return (err) ? err : count;
 }
 
 static struct fb_ops hecubafb_ops = {