[PATCH] uio: add support for ioctl

[Stephen Hemminger <stephen@networkplumber.org>]

Allow UIO device specific driver to provide ioctl interface.
This mechanism is used in DPDK uio_msi driver to allow creating
VFIO like events.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

--- a/drivers/uio/uio.c	2015-05-18 10:29:00.097129278 -0700
+++ b/drivers/uio/uio.c	2015-05-18 10:29:00.097129278 -0700
@@ -576,6 +576,20 @@ static ssize_t uio_write(struct file *fi
 	return retval ? retval : sizeof(s32);
 }
 
+static long uio_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+	struct uio_listener *listener = filep->private_data;
+	struct uio_device *idev = listener->dev;
+
+	if (!idev->info)
+		return -EIO;
+
+	if (!idev->info->ioctl)
+		return -ENOTTY;
+
+	return idev->info->ioctl(idev->info, cmd, arg);
+}
+
 static int uio_find_mem_index(struct vm_area_struct *vma)
 {
 	struct uio_device *idev = vma->vm_private_data;
@@ -712,6 +726,7 @@ static const struct file_operations uio_
 	.write		= uio_write,
 	.mmap		= uio_mmap,
 	.poll		= uio_poll,
+	.unlocked_ioctl	= uio_ioctl,
 	.fasync		= uio_fasync,
 	.llseek		= noop_llseek,
 };
--- a/include/linux/uio_driver.h	2015-05-18 10:29:00.097129278 -0700
+++ b/include/linux/uio_driver.h	2015-05-18 10:29:00.097129278 -0700
@@ -89,6 +89,7 @@ struct uio_device {
  * @mmap:		mmap operation for this uio device
  * @open:		open operation for this uio device
  * @release:		release operation for this uio device
+ * @ioctl:		ioctl handler
  * @irqcontrol:		disable/enable irqs when 0/1 is written to /dev/uioX
  */
 struct uio_info {
@@ -105,6 +106,7 @@ struct uio_info {
 	int (*open)(struct uio_info *info, struct inode *inode);
 	int (*release)(struct uio_info *info, struct inode *inode);
 	int (*irqcontrol)(struct uio_info *info, s32 irq_on);
+	int (*ioctl)(struct uio_info *info, unsigned int cmd, unsigned long arg);
 };
 
 extern int __must_check