---

yaml
---
r: 104768
b: refs/heads/master
c: 328a14e
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 934da4766e5f72797118f7c014efaef567a812fc
+refs/heads/master: 328a14e70e7f46997cb50d4258dd93d5377f98c6

trunk/Documentation/DocBook/uio-howto.tmpl

@@ -29,6 +29,12 @@
 </abstract>
 
 <revhistory>
+	<revision>
+	<revnumber>0.5</revnumber>
+	<date>2008-05-22</date>
+	<authorinitials>hjk</authorinitials>
+	<revremark>Added description of write() function.</revremark>
+	</revision>
 	<revision>
 	<revnumber>0.4</revnumber>
 	<date>2007-11-26</date>
@@ -64,7 +70,7 @@
 <?dbhtml filename="copyright.html"?>
 <title>Copyright and License</title>
 <para>
-      Copyright (c) 2006 by Hans-Jürgen Koch.</para>
+      Copyright (c) 2006-2008 by Hans-Jürgen Koch.</para>
 <para>
 This documentation is Free Software licensed under the terms of the
 GPL version 2.
@@ -189,6 +195,30 @@ interested in translating it, please email me
 	represents the total interrupt count. You can use this number
 	to figure out if you missed some interrupts.
 	</para>
+	<para>
+	For some hardware that has more than one interrupt source internally,
+	but not separate IRQ mask and status registers, there might be
+	situations where userspace cannot determine what the interrupt source
+	was if the kernel handler disables them by writing to the chip's IRQ
+	register. In such a case, the kernel has to disable the IRQ completely
+	to leave the chip's register untouched. Now the userspace part can
+	determine the cause of the interrupt, but it cannot re-enable
+	interrupts. Another cornercase is chips where re-enabling interrupts
+	is a read-modify-write operation to a combined IRQ status/acknowledge
+	register. This would be racy if a new interrupt occurred
+	simultaneously.
+	</para>
+	<para>
+	To address these problems, UIO also implements a write() function. It
+	is normally not used and can be ignored for hardware that has only a
+	single interrupt source or has separate IRQ mask and status registers.
+	If you need it, however, a write to <filename>/dev/uioX</filename>
+	will call the <function>irqcontrol()</function> function implemented
+	by the driver. You have to write a 32-bit value that is usually either
+	0 or 1 to disable or enable interrupts. If a driver does not implement
+	<function>irqcontrol()</function>, <function>write()</function> will
+	return with <varname>-ENOSYS</varname>.
+	</para>
 
 	<para>
 	To handle interrupts properly, your custom kernel module can
@@ -362,6 +392,14 @@ device is actually used.
 <function>open()</function>, you will probably also want a custom
 <function>release()</function> function.
 </para></listitem>
+
+<listitem><para>
+<varname>int (*irqcontrol)(struct uio_info *info, s32 irq_on)
+</varname>: Optional. If you need to be able to enable or disable
+interrupts from userspace by writing to <filename>/dev/uioX</filename>,
+you can implement this function. The parameter <varname>irq_on</varname>
+will be 0 to disable interrupts and 1 to enable them.
+</para></listitem>
 </itemizedlist>
 
 <para>

trunk/drivers/uio/uio.c

@@ -427,6 +427,31 @@ static ssize_t uio_read(struct file *filep, char __user *buf,
 	return retval;
 }
 
+static ssize_t uio_write(struct file *filep, const char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	struct uio_listener *listener = filep->private_data;
+	struct uio_device *idev = listener->dev;
+	ssize_t retval;
+	s32 irq_on;
+
+	if (idev->info->irq == UIO_IRQ_NONE)
+		return -EIO;
+
+	if (count != sizeof(s32))
+		return -EINVAL;
+
+	if (!idev->info->irqcontrol)
+		return -ENOSYS;
+
+	if (copy_from_user(&irq_on, buf, count))
+		return -EFAULT;
+
+	retval = idev->info->irqcontrol(idev->info, irq_on);
+
+	return retval ? retval : sizeof(s32);
+}
+
 static int uio_find_mem_index(struct vm_area_struct *vma)
 {
 	int mi;
@@ -546,6 +571,7 @@ static const struct file_operations uio_fops = {
 	.open		= uio_open,
 	.release	= uio_release,
 	.read		= uio_read,
+	.write		= uio_write,
 	.mmap		= uio_mmap,
 	.poll		= uio_poll,
 	.fasync		= uio_fasync,

trunk/include/linux/uio_driver.h

@@ -53,6 +53,7 @@ struct uio_device;
  * @mmap:		mmap operation for this uio device
  * @open:		open operation for this uio device
  * @release:		release operation for this uio device
+ * @irqcontrol:		disable/enable irqs when 0/1 is written to /dev/uioX
  */
 struct uio_info {
 	struct uio_device	*uio_dev;
@@ -66,6 +67,7 @@ struct uio_info {
 	int (*mmap)(struct uio_info *info, struct vm_area_struct *vma);
 	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);
 };
 
 extern int __must_check