s390/ap: modularize ap bus

There is no hard requirement to have the ap bus statically in the
kernel, so add an option to compile it as module.

Cc: Tony Krowiak <[e-mail]>
Cc: Halil Pasic <[e-mail]>
Signed-off-by: Holger Dengler <[e-mail]>
Reviewed-by: Harald Freudenberger <[e-mail]>
Reviewed-by: Anthony Krowiak <[e-mail]>
Signed-off-by: Alexander Gordeev <[e-mail]>

Documentation/arch/s390/vfio-ap.rst

···
    following Kconfig elements selected:
    * IOMMU_SUPPORT
    * S390
-   * ZCRYPT
+   * AP
    * VFIO
    * KVM
 

arch/s390/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called eadm_sch.
 
+config AP
+	def_tristate y
+	prompt "Support for Adjunct Processors (ap)"
+	help
+	  This driver allows usage to Adjunct Processor (AP) devices via
+	  the ap bus, cards and queues. Supported Adjunct Processors are
+	  the CryptoExpress Cards (CEX).
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ap.
+
+	  If unsure, say Y (default).
+
 config VFIO_CCW
 	def_tristate n
 	prompt "Support for VFIO-CCW subchannels"
···
 	prompt "VFIO support for AP devices"
 	depends on KVM
 	depends on VFIO
-	depends on ZCRYPT
+	depends on AP
 	select VFIO_MDEV
 	help
 	  This driver grants access to Adjunct Processor (AP) devices

drivers/crypto/Kconfig

···
 config ZCRYPT
 	tristate "Support for s390 cryptographic adapters"
 	depends on S390
+	depends on AP
 	select HW_RANDOM
 	help
 	  Select this option if you want to enable support for

drivers/s390/char/Makefile

···
 
 obj-$(CONFIG_PCI) += sclp_pci.o
 
-obj-$(subst m,y,$(CONFIG_ZCRYPT)) += sclp_ap.o
+obj-$(subst m,y,$(CONFIG_AP)) += sclp_ap.o
 
 obj-$(CONFIG_VMLOGRDR) += vmlogrdr.o
 obj-$(CONFIG_VMCP) += vmcp.o

drivers/s390/crypto/Makefile

···
 #
 
 ap-objs := ap_bus.o ap_card.o ap_queue.o
-obj-$(subst m,y,$(CONFIG_ZCRYPT)) += ap.o
+obj-$(CONFIG_AP) += ap.o
 # zcrypt_api.o and zcrypt_msgtype*.o depend on ap.o
 zcrypt-objs := zcrypt_api.o zcrypt_card.o zcrypt_queue.o
 zcrypt-objs += zcrypt_msgtype6.o zcrypt_msgtype50.o

drivers/s390/crypto/ap_bus.c

···
 #include "ap_bus.h"
 #include "ap_debug.h"
 
-/*
- * Module parameters; note though this file itself isn't modular.
- */
+MODULE_AUTHOR("IBM Corporation");
+MODULE_DESCRIPTION("Adjunct Processor Bus driver");
+MODULE_LICENSE("GPL");
+
 int ap_domain_index = -1;	/* Adjunct Processor Domain Index */
 static DEFINE_SPINLOCK(ap_domain_lock);
 module_param_named(domain, ap_domain_index, int, 0440);
···
 	}
 }
 
+static inline void __exit ap_async_exit(void)
+{
+	if (ap_thread_flag)
+		ap_poll_thread_stop();
+	chsc_notifier_unregister(&ap_bus_nb);
+	cancel_work(&ap_scan_bus_work);
+	hrtimer_cancel(&ap_poll_timer);
+	timer_delete(&ap_scan_bus_timer);
+}
+
 static inline int __init ap_async_init(void)
 {
 	int rc;
···
 	ap_debug_exit();
 	return rc;
 }
-device_initcall(ap_module_init);
+
+static void __exit ap_module_exit(void)
+{
+	ap_async_exit();
+	ap_irq_exit();
+	root_device_unregister(ap_root_device);
+	bus_unregister(&ap_bus_type);
+	ap_debug_exit();
+}
+
+module_init(ap_module_init);
+module_exit(ap_module_exit);