Q:

restrict some quantity for adding to cart

we needed "pre-order/Back order" feature [ user can buy out-of-stock Products ]
so we wrote custom module.  how it works is , if we set value
"yes" to pre order attribute, it will  allow for pre-order,
for "NO", it will not show "Pre order" button in view page. 
but problem is user can enter any number of quantity & add to cart items. 
what we need is what quantity we enter in backend, only it should allow that much quantity to add-to-cart. 
<? php $_collectionSize = $_productCollection->count() ? >
    <? php $_columnCount = $this->getColumnCount(); ? >
    <? php $i=0; foreach ($_productCollection as $_product): ? >
        <? php if ($i++%$_columnCount==0): ? >
        <ul class="products-grid">
        <? php endif ? >
            <li class="item<?php if(($i-1)%$_columnCount==0): ? > first<?php elseif($i%$_columnCount==0): ? > last<?php endif; ? >">

                <h2 class="product-name"><a href="<?php echo $_product->getProductUrl() ? >" title="<?php echo $this->stripTags($_product->getName(), null, true) ? >"><? php echo $_helper->productAttribute($_product, $_product->getName(), 'name') ? ></a></h2>

                <? php echo $this->getPriceHtml($_product, true) ? >
                <div class="actions">
                    <? php if($_product->isSaleable()): ? >
                        <? php if($_product->getPreOrder()): ? >
                        <button type="button" title="<?php echo $this->__('Pre-Order') ? >" class="button btn-cart" onclick="setLocation('<?php echo $this->getAddToCartUrl($_product) ? >')"><span><span><?php echo $this->__('Pre-Order') ? ></span></span></button>

                        <? php endif; ? >
                    <? php else: ? >
                        <p class="availability out-of-stock"><span><?php echo $this->__('') ? ></span></p>
                    <? php endif; ? >

                </div>
            </li>
        <? php if ($i%$_columnCount==0 || $i==$_collectionSize): ? >
        </ul>
        <? php endif ? >
        <? php endforeach ? >
        <script type="text/javascript">decorateGeneric($$('ul.products-grid'), ['odd','even','first','last'])</script>
    <? php endif; ? >

complete code : http://pasted.co/8c8e0763

A:

You need to set maximum qty allowed in shopping cart in inventory section when adding products as shown in screen shot. 
link

