coresight: removing bind/unbind options from sysfs

The coresight drivers have absolutely no control over bind and unbind
operations triggered from sysfs. The operations simply can't be
cancelled or denied event when one or several tracing sessions are
under way.  Since the memory associated to individual device is
invariably freed, the end result is a kernel crash when the path from
source to sink is travelled again as demonstrated here[1].

One solution could be to keep track of all the path (i.e tracing
session) that get created and iterate through the elements of those path
looking for the coresight device that is being removed.  This proposition
doesn't scale well since there is no upper bound on the amount of
concurrent trace session that can be created.

With the above in mind, this patch prevent devices from being unbounded
from their driver by using the driver->suppress_bind_attr option.  That way
trace sessions can be managed without fearing to loose devices.

Since device can't be removed anymore the xyz_remove() functions found in
each driver is also removed.

[1]. http://www.spinics.net/lists/arm-kernel/msg474952.html

Reported-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 14 deletions

diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index a57c7ec1661f..570d96815f78 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -770,19 +770,6 @@ err_devm_kzalloc:
 	return ret;
 }
 
-static int tmc_remove(struct amba_device *adev)
-{
-	struct tmc_drvdata *drvdata = amba_get_drvdata(adev);
-
-	misc_deregister(&drvdata->miscdev);
-	coresight_unregister(drvdata->csdev);
-	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
-		dma_free_coherent(drvdata->dev, drvdata->size,
-				  &drvdata->paddr, GFP_KERNEL);
-
-	return 0;
-}
-
 static struct amba_id tmc_ids[] = {
 	{
 		.id     = 0x0003b961,
@@ -795,9 +782,9 @@ static struct amba_driver tmc_driver = {
 	.drv = {
 		.name   = "coresight-tmc",
 		.owner  = THIS_MODULE,
+		.suppress_bind_attrs = true,
 	},
 	.probe		= tmc_probe,
-	.remove		= tmc_remove,
 	.id_table	= tmc_ids,
 };