woocommerce_add_to_cart_quantity filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_add_to_cart_quantity', 'filter_function_name_9461', 10, 2 );
function filter_function_name_9461( $quantity, $product_id ){
	// filter...

	return $quantity;
}

$quantity

-

$product_id

-

Where the hook is called

$quantity     = apply_filters( 'woocommerce_add_to_cart_quantity', $quantity, $product_id );

Where in WP core the hook is used WooCommerce