Re: [PATCH 1/2] staging: comedi: fix auto-unconfig kernel error

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On 27/12/13 23:49, Bernd Porr wrote:
Signed-off-by: Bernd Porr <mail@xxxxxxxxxxxxxxx>

"Signed-off-by" should be after the description. :)


Merging un-registering of both the subdevices and the
main comedi device into one function and the module which
actually associated with it. The kernel oops observed before
was because the main device was un-registered first and
then the subdevices which were then no longer valid.
This has been also tested with 'comedi_config -r'.

It might work with 'comedi_config -r' for auto-configured devices, but I don't think it will work for manually configured "legacy" devices (e.g. a "comedi_test" device configured by 'comedi_config /dev/comedi0 comedi_test' when the 'comedi_num_legacy_minors' module parameter is greater than 0). comedi_free_board_dev() wouldn't be called in that case when the device is unconfigured later, because the legacy comedi devices persist until the comedi module is unloaded, whereas the auto-configured comedi devices only persist while the low-level device remains attached (more or less - they now also persist while referenced by an unreleased file object).

---
  drivers/staging/comedi/comedi_fops.c | 19 +++++++++++++++++++
  drivers/staging/comedi/drivers.c     | 18 ------------------
  2 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index f3d59e2..2680b72 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -141,7 +141,26 @@ static struct comedi_device *comedi_clear_board_minor(unsigned minor)

  static void comedi_free_board_dev(struct comedi_device *dev)
  {
+	int i;
+	struct comedi_subdevice *s;
+
  	if (dev) {
+		if (dev->subdevices) {
+			for (i = 0; i < dev->n_subdevices; i++) {
+				s = &dev->subdevices[i];
+				if (s->runflags & SRF_FREE_SPRIV)
+					kfree(s->private);
+				comedi_free_subdevice_minor(s);
+				if (s->async) {
+					comedi_buf_alloc(dev, s, 0);
+					kfree(s->async);
+				}
+			}
+			kfree(dev->subdevices);
+			dev->subdevices = NULL;
+			dev->n_subdevices = 0;
+		}
+
  		if (dev->class_dev) {
  			device_destroy(comedi_class,
  				       MKDEV(COMEDI_MAJOR, dev->minor));
diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 4964d2a..d6dc58a 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -97,24 +97,6 @@ EXPORT_SYMBOL_GPL(comedi_alloc_subdevices);

  static void cleanup_device(struct comedi_device *dev)
  {
-	int i;
-	struct comedi_subdevice *s;
-
-	if (dev->subdevices) {
-		for (i = 0; i < dev->n_subdevices; i++) {
-			s = &dev->subdevices[i];
-			if (s->runflags & SRF_FREE_SPRIV)
-				kfree(s->private);
-			comedi_free_subdevice_minor(s);
-			if (s->async) {
-				comedi_buf_alloc(dev, s, 0);
-				kfree(s->async);
-			}
-		}
-		kfree(dev->subdevices);
-		dev->subdevices = NULL;
-		dev->n_subdevices = 0;
-	}
  	kfree(dev->private);
  	dev->private = NULL;
  	dev->driver = NULL;



--
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@xxxxxxxxx>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
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