[PATCH v2 1/2] parport: return of attach and parport_register_driver

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

as of now, we are not checking if attach or parport_register_driver
has succeeded or failed. But attach can fail in the places where they
have been used. Lets create an attach_ret where we will check the
return of attach, and if attach fails then parport_register_driver
should also fail. We can have multiple parallel port, like parport0,
parport1 and one driver may decide to only use parport0. so we mark
attach as failed only if it has never returned a 0.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
---
 drivers/parport/share.c | 27 ++++++++++++++++++++++-----
 include/linux/parport.h |  1 +
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index 3fa6624..4aab733 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -143,28 +143,45 @@ static void get_lowlevel_driver (void)
  *	pointer it must call parport_get_port() to do so.  Calling
  *	parport_register_device() on that port will do this for you.
  *
+ *	The attach_ret() function will check for the return value.
+ *
  *	The driver's detach() function may block.  The port that
  *	detach() is given will be valid for the duration of the
  *	callback, but if the driver wants to take a copy of the
  *	pointer it must call parport_get_port() to do so.
  *
- *	Returns 0 on success.  Currently it always succeeds.
+ *	Returns 0 on success.
  **/
 
 int parport_register_driver (struct parport_driver *drv)
 {
 	struct parport *port;
+	bool attached = false;
+	int err, ret = 0;
 
 	if (list_empty(&portlist))
 		get_lowlevel_driver ();
 
 	mutex_lock(&registration_lock);
-	list_for_each_entry(port, &portlist, list)
-		drv->attach(port);
-	list_add(&drv->list, &drivers);
+	list_for_each_entry(port, &portlist, list) {
+		if (drv->attach_ret) {
+			err = drv->attach_ret(port);
+		} else {
+			drv->attach(port);
+			err = 0;
+		}
+		if (err == 0)
+			attached = true;
+		else
+			ret = err;
+	}
+	if (attached) {
+		list_add(&drv->list, &drivers);
+		ret = 0;
+	}
 	mutex_unlock(&registration_lock);
 
-	return 0;
+	return ret;
 }
 
 /**
diff --git a/include/linux/parport.h b/include/linux/parport.h
index c22f125..cc869ec 100644
--- a/include/linux/parport.h
+++ b/include/linux/parport.h
@@ -250,6 +250,7 @@ struct parport {
 struct parport_driver {
 	const char *name;
 	void (*attach) (struct parport *);
+	int (*attach_ret)(struct parport *);
 	void (*detach) (struct parport *);
 	struct list_head list;
 };
-- 
1.8.1.2