powerpc/spufs: Use simple_write_to_buffer

Simplify several write fileoperations for spufs by using
simple_write_to_buffer().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/cell/spufs/file.c

@@ -219,24 +219,17 @@ spufs_mem_write(struct file *file, const char __user *buffer,
 	loff_t pos = *ppos;
 	int ret;
 
-	if (pos < 0)
-		return -EINVAL;
 	if (pos > LS_SIZE)
 		return -EFBIG;
-	if (size > LS_SIZE - pos)
-		size = LS_SIZE - pos;
 
 	ret = spu_acquire(ctx);
 	if (ret)
 		return ret;
 
 	local_store = ctx->ops->get_ls(ctx);
-	ret = copy_from_user(local_store + pos, buffer, size);
+	size = simple_write_to_buffer(local_store, LS_SIZE, ppos, buffer, size);
 	spu_release(ctx);
 
-	if (ret)
-		return -EFAULT;
-	*ppos = pos + size;
 	return size;
 }
 
@@ -574,18 +567,15 @@ spufs_regs_write(struct file *file, const char __user *buffer,
 	if (*pos >= sizeof(lscsa->gprs))
 		return -EFBIG;
 
-	size = min_t(ssize_t, sizeof(lscsa->gprs) - *pos, size);
-	*pos += size;
-
 	ret = spu_acquire_saved(ctx);
 	if (ret)
 		return ret;
 
-	ret = copy_from_user((char *)lscsa->gprs + *pos - size,
-			     buffer, size) ? -EFAULT : size;
+	size = simple_write_to_buffer(lscsa->gprs, sizeof(lscsa->gprs), pos,
+					buffer, size);
 
 	spu_release_saved(ctx);
-	return ret;
+	return size;
 }
 
 static const struct file_operations spufs_regs_fops = {
@@ -630,18 +620,15 @@ spufs_fpcr_write(struct file *file, const char __user * buffer,
 	if (*pos >= sizeof(lscsa->fpcr))
 		return -EFBIG;
 
-	size = min_t(ssize_t, sizeof(lscsa->fpcr) - *pos, size);
-
 	ret = spu_acquire_saved(ctx);
 	if (ret)
 		return ret;
 
-	*pos += size;
-	ret = copy_from_user((char *)&lscsa->fpcr + *pos - size,
-			     buffer, size) ? -EFAULT : size;
+	size = simple_write_to_buffer(&lscsa->fpcr, sizeof(lscsa->fpcr), pos,
+					buffer, size);
 
 	spu_release_saved(ctx);
-	return ret;
+	return size;
 }
 
 static const struct file_operations spufs_fpcr_fops = {