crypto: omap-sham - make queue length configurable

Crypto driver queue size can now be configured from userspace. This
allows optimizing the queue usage based on use case. Default queue
size is still 10 entries.
Signed-off-by: NTero Kristo <t-kristo@ti.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/omap-sham.c

@@ -2051,9 +2051,47 @@ static ssize_t fallback_store(struct device *dev, struct device_attribute *attr,
 	return size;
 }
 
+static ssize_t queue_len_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct omap_sham_dev *dd = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dd->queue.max_qlen);
+}
+
+static ssize_t queue_len_store(struct device *dev,
+			       struct device_attribute *attr, const char *buf,
+			       size_t size)
+{
+	struct omap_sham_dev *dd = dev_get_drvdata(dev);
+	ssize_t status;
+	long value;
+	unsigned long flags;
+
+	status = kstrtol(buf, 0, &value);
+	if (status)
+		return status;
+
+	if (value < 1)
+		return -EINVAL;
+
+	/*
+	 * Changing the queue size in fly is safe, if size becomes smaller
+	 * than current size, it will just not accept new entries until
+	 * it has shrank enough.
+	 */
+	spin_lock_irqsave(&dd->lock, flags);
+	dd->queue.max_qlen = value;
+	spin_unlock_irqrestore(&dd->lock, flags);
+
+	return size;
+}
+
+static DEVICE_ATTR_RW(queue_len);
 static DEVICE_ATTR_RW(fallback);
 
 static struct attribute *omap_sham_attrs[] = {
+	&dev_attr_queue_len.attr,
 	&dev_attr_fallback.attr,
 	NULL,
 };