[PATCH v4 4/6] platform/x86/amd/hsmp: Clear mdev.this_device on deregister

[Muralidhara M K]

misc_deregister() destroys the device but leaves miscdevice.this_device
pointing at the freed struct device. Clear it so any later check of
this_device, and a subsequent re-register, does not observe a stale
pointer. An upcoming change uses this_device to track whether /dev/hsmp is
registered across the shared ACPI sockets and relies on it being NULL after
deregister.

Signed-off-by: Muralidhara M K <muralidhara.mk@xxxxxxx>
---
 drivers/platform/x86/amd/hsmp/hsmp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/platform/x86/amd/hsmp/hsmp.c b/drivers/platform/x86/amd/hsmp/hsmp.c
index 10fc21887308..ccd19c7bf115 100644
--- a/drivers/platform/x86/amd/hsmp/hsmp.c
+++ b/drivers/platform/x86/amd/hsmp/hsmp.c
@@ -531,6 +531,12 @@ EXPORT_SYMBOL_NS_GPL(hsmp_misc_register, "AMD_HSMP");
 void hsmp_misc_deregister(void)
 {
 	misc_deregister(&hsmp_pdev.mdev);
+	/*
+	 * misc_deregister() leaves mdev.this_device pointing at the freed
+	 * device. Clear it so a later re-register is not skipped on a stale
+	 * pointer.
+	 */
+	hsmp_pdev.mdev.this_device = NULL;
 }
 EXPORT_SYMBOL_NS_GPL(hsmp_misc_deregister, "AMD_HSMP");
 
-- 
2.34.1