[PATCH 17/37] staging: comedi: replace __comedi_device_detach()

[Ian Abbott]

`comedi_device_detach()` does nothing if the `struct comedi_device`'s
`attached` member is false, otherwise it calls
`__comedi_device_detach()` to do the real work.
`__comedi_device_detach()` is called from various other functions in
"drivers.c" (`comedi_device_postconfig()`, `comedi_device_attach()`, and
`comedi_auto_config()`) to bypass the check for the `attached` member
being false.

If we make `__comedi_device_detach()` safe to call when the `attached`
member is already false, we can remove the check in
`comedi_device_detach()`, subsume `__comedi_device_detach()` within
`comedi_device_detach()`, and replace all the calls to
`__comedi_device_detach()` with calls to `comedi_device_detach()`.

In fact, it is already safe to call `__comedi_device_detach()` when the
`attached` member is false.  We just need to remove the warning message
it outputs when the `driver` member is NULL.  Then the function becomes
idempotent without outputting spurious warnings.  (It is idempotent
because `dev->driver->detach()` will only be called once at most and the
call to `cleanup_device()` is idempotent itself.)

Combine `comedi_device_detach()` with `__comedi_device_detach()`,
removing the check for the `attached` member being false and removing
the warning about the `driver` member being NULL, and replace all calls
to `__comedi_device_detach()` with calls to the combined
`comedi_device_detach()`.

A beneficial side-effect of the above change is that a call to
`comedi_device_detach()` will always result in a call to
`cleanup_device()` and so always result in a call to
`comedi_clear_hw_dev()`.  We will make use of this beneficial
side-effect in a later patch.

Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
---
 drivers/staging/comedi/drivers.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 6f232b8..cf1ca82 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -119,24 +119,14 @@ static void cleanup_device(struct comedi_device *dev)
 	comedi_clear_hw_dev(dev);
 }
 
-static void __comedi_device_detach(struct comedi_device *dev)
+void comedi_device_detach(struct comedi_device *dev)
 {
 	dev->attached = false;
 	if (dev->driver)
 		dev->driver->detach(dev);
-	else
-		dev_warn(dev->class_dev,
-			 "BUG: dev->driver=NULL in comedi_device_detach()\n");
 	cleanup_device(dev);
 }
 
-void comedi_device_detach(struct comedi_device *dev)
-{
-	if (!dev->attached)
-		return;
-	__comedi_device_detach(dev);
-}
-
 static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s)
 {
 	return -EINVAL;
@@ -283,7 +273,7 @@ static int comedi_device_postconfig(struct comedi_device *dev)
 
 	ret = __comedi_device_postconfig(dev);
 	if (ret < 0) {
-		__comedi_device_detach(dev);
+		comedi_device_detach(dev);
 		return ret;
 	}
 	if (!dev->board_name) {
@@ -396,7 +386,7 @@ int comedi_device_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	dev->driver = driv;
 	ret = driv->attach(dev, it);
 	if (ret < 0) {
-		__comedi_device_detach(dev);
+		comedi_device_detach(dev);
 		module_put(dev->driver->module);
 		return ret;
 	}
@@ -439,7 +429,7 @@ int comedi_auto_config(struct device *hardware_device,
 	comedi_dev->driver = driver;
 	ret = driver->auto_attach(comedi_dev, context);
 	if (ret < 0)
-		__comedi_device_detach(comedi_dev);
+		comedi_device_detach(comedi_dev);
 	else
 		ret = comedi_device_postconfig(comedi_dev);
 	mutex_unlock(&comedi_dev->mutex);
-- 
1.8.1.5