From bda1469e1138569325fa8768b50cffbca3454639 Mon Sep 17 00:00:00 2001
From: David Schleef <ds@schleef.org>
Date: Thu, 5 Jul 2001 05:33:16 +0000
Subject: [PATCH] Rewrote checking in comedi_fop_open(), fixed spinlock init
 problem.

---
 comedi/comedi_fops.c      | 24 ++++++++++++++++++++----
 comedi/drivers.c          |  1 +
 include/linux/comedidev.h |  1 +
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/comedi/comedi_fops.c b/comedi/comedi_fops.c
index 57b5d18c..bf395800 100644
--- a/comedi/comedi_fops.c
+++ b/comedi/comedi_fops.c
@@ -1621,25 +1621,40 @@ static int comedi_fop_open(struct inode *inode,struct file *file)
 {
 	kdev_t minor=MINOR(inode->i_rdev);
 	comedi_device *dev;
-	static int in_comedi_open=0;
 	char mod[32];
 
 	if(minor>=COMEDI_NDEVICES)return -ENODEV;
 
 	dev=comedi_get_device_by_minor(minor);
+
+	/* This is slightly hacky, but we want module autoloading
+	 * to work for root. 
+	 * case: user opens device, attached -> ok
+	 * case: user opens device, unattached, in_request_module=0 -> autoload
+	 * case: user opens device, unattached, in_request_module=1 -> fail
+	 * case: root opens device, attached -> ok
+	 * case: root opens device, unattached, in_request_module=1 -> ok
+	 *   (typically called from modprobe)
+	 * case: root opens device, unattached, in_request_module=0 -> autoload
+	 *
+	 * The last could be changed to "-> ok", which would deny root
+	 * autoloading.
+	 */
 	if(dev->attached)
 		goto ok;
-	if(in_comedi_open && suser())
+	if(!suser() && dev->in_request_module)
+		return -ENODEV;
+	if(suser() && dev->in_request_module)
 		goto ok;
 
-	in_comedi_open=1;
+	dev->in_request_module=1;
 
 	sprintf(mod,"char-major-%i-%i",COMEDI_MAJOR,minor);
 #ifdef CONFIG_KMOD
 	request_module(mod);
 #endif
 
-	in_comedi_open=0;
+	dev->in_request_module=0;
 
 	if(dev->attached || suser())
 		goto ok;
@@ -1775,6 +1790,7 @@ int comedi_init(void)
 	memset(comedi_devices,0,sizeof(comedi_device)*COMEDI_NDEVICES);
 	for(i=0;i<COMEDI_NDEVICES;i++){
 		comedi_devices[i].minor=i;
+		spin_lock_init(&(comedi_devices[i].spinlock));
 	}
 #if 0
 	init_polling();
diff --git a/comedi/drivers.c b/comedi/drivers.c
index 6967bd35..01b9707f 100644
--- a/comedi/drivers.c
+++ b/comedi/drivers.c
@@ -107,6 +107,7 @@ int comedi_device_attach(comedi_device *dev,comedi_devconfig *it)
 	minor = dev->minor;
 	use_count = dev->use_count;
 	memset(dev,0,sizeof(comedi_device));
+	spin_lock_init(&dev->spinlock);
 	dev->minor=minor;
 	dev->use_count = use_count;
 
diff --git a/include/linux/comedidev.h b/include/linux/comedidev.h
index 5df9e908..df5fd928 100644
--- a/include/linux/comedidev.h
+++ b/include/linux/comedidev.h
@@ -162,6 +162,7 @@ struct comedi_device_struct{
 	int attached;
 	int rt;
 	spinlock_t spinlock;
+	int in_request_module;
 
 	int n_subdevices;
 	comedi_subdevice *subdevices;
-- 
2.26.2