MAP_SHARED, buf->bus_address);
        dev_priv->mmap_buffer = NULL;
        filp->f_op = old_fops;
-       if ((unsigned long)buf_priv->virtual > -1024UL) {
+       if (IS_ERR(buf_priv->virtual)) {
                /* Real error */
                DRM_ERROR("mmap error\n");
-               retcode = (signed int)buf_priv->virtual;
+               retcode = PTR_ERR(buf_priv->virtual);
                buf_priv->virtual = NULL;
        }
        up_write(¤t->mm->mmap_sem);
                    ((GFX_OP_PRIMITIVE | prim | ((used / 4) - 2)));
 
                if (used & 4) {
-                       *(u32 *) ((u32) buf_priv->kernel_virtual + used) = 0;
+                       *(u32 *) ((char *) buf_priv->kernel_virtual + used) = 0;
                        used += 4;
                }
 
 
        if (buf_priv->currently_mapped == I810_BUF_MAPPED) {
                if (used & 4) {
-                       *(u32 *) ((u32) buf_priv->virtual + used) = 0;
+                       *(u32 *) ((char *) buf_priv->virtual + used) = 0;
                        used += 4;
                }
 
 
        if (IS_ERR((void *)virtual)) {  /* ugh */
                /* Real error */
                DRM_ERROR("mmap error\n");
-               retcode = virtual;
+               retcode = PTR_ERR((void *)virtual);
                buf_priv->virtual = NULL;
        } else {
                buf_priv->virtual = (void __user *)virtual;