HACK: Use "0xDE" instead of "0xDEC" for the major number

Workaround the issues that the com_on_air_cs.ko kernel module could not be loaded:

insmod com_on_air_cs.ko
-> insmod: ERROR: could not insert module com_on_air_cs.ko: Invalid parameters

dmesg
-> CHRDEV "com_on_air_cs" major requested (3564) is greater than the maximum (511)

CHRDEV_MAJOR_MAX is set to "512" in the kernel
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/include/linux/fs.h
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/fs/char_dev.c

com_on_air_cs uses 0xDEC (int 3564) which is greater than this maximum.
 -> Workaround: Use 0xDE (int  222) instead.

This already conflicts with a reserved (but probably not widely used) allocation:
https://www.kernel.org/doc/Documentation/admin-guide/devices.txt

Real fix:
* Use Dynamic Major Number allocation instead of assigning a static one.

com-on-air_cs-linux/Makefile

@@ -32,7 +32,7 @@ reload:
 
 node: $(NODE)
 $(NODE):
-	mknod $@ --mode 660 c 3564 0  ###  3564 == 0xDEC
+	mknod $@ --mode 660 c 222 0  ###  222 == 0xDE
 #	chgrp dect $(NODE)
 
 read: node coa_read

com-on-air_cs-linux/com_on_air.c

@@ -20,6 +20,7 @@
 #include <linux/crc32.h>
 #include <linux/kfifo.h>
 #include <linux/poll.h>
+#include <linux/version.h>
 
 #include <pcmcia/cistpl.h>
 #include <pcmcia/ciscode.h>
@@ -406,7 +407,11 @@ com_on_air_irq_handler(int irq, void *dev_id)
 
 	uint8_t dip_irq = 0;
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+	jiffies_to_timespec64(jiffies, &dev->irq_timestamp);
+#else
 	jiffies_to_timespec(jiffies, &dev->irq_timestamp);
+#endif
 	dev->irq_count++;
 
 	switch(dev->operation_mode & COA_MODEMASK)
@@ -480,7 +485,7 @@ static int com_on_air_probe (struct pcmcia_device *link)
 
 	dev->links[0]   = link;
         dev->memsize[0] = resource_size(link->resource[2]);
-        dev->membase[0] = ioremap_nocache(link->resource[2]->start, resource_size(link->resource[2]));
+        dev->membase[0] = ioremap(link->resource[2]->start, resource_size(link->resource[2]));
 
 	if (!dev->membase[0])
 	{
@@ -740,7 +745,7 @@ static int __init init_com_on_air_cs(void)
 		goto init_out_3;
 	}
 
-	ret = register_chrdev(0xDEC, COA_DEVICE_NAME, &coa_fops);
+	ret = register_chrdev(0xDE, COA_DEVICE_NAME, &coa_fops);
 	if (ret < 0)
 	{
 		printk("couldn't register_chrdev()\n");
@@ -768,7 +773,7 @@ static int __init init_com_on_air_cs(void)
 init_out_0:
         kfifo_free(&dev->rx_fifo);
 init_out_1:
-	unregister_chrdev(0xDEC, COA_DEVICE_NAME);
+	unregister_chrdev(0xDE, COA_DEVICE_NAME);
 init_out_2:
 	pcmcia_unregister_driver(&coa_driver);
 init_out_3:
@@ -782,7 +787,7 @@ static void __exit exit_com_on_air_cs(void)
 
 	if (!dev) return;
 
-	unregister_chrdev(0xDEC, COA_DEVICE_NAME);
+	unregister_chrdev(0xDE, COA_DEVICE_NAME);
 
 	pcmcia_unregister_driver(&coa_driver);
 

com-on-air_cs-linux/com_on_air.h

@@ -16,6 +16,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/version.h>
 
 struct coa_info
 {
@@ -24,7 +25,11 @@ struct coa_info
 
 	int                     irq;
 	int                     irq_count;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+	struct timespec64       irq_timestamp;
+#else
 	struct timespec         irq_timestamp;
+#endif
 
 	struct pcmcia_device    *links[2];
 

com-on-air_cs-linux/sc14421_sniffer.h

@@ -29,6 +29,8 @@
 #include "dect.h"
 #include "com_on_air.h"
 
+#include <linux/version.h>
+
 struct sniffer_cfg
 {
 	int			snifftype;
@@ -57,7 +59,11 @@ struct sniffed_packet
 	unsigned char     channel;
 	unsigned char     slot;
 	unsigned char     frameflags;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+	struct timespec64 timestamp;
+#else
 	struct timespec   timestamp;
+#endif
 	unsigned char     data[53];
 };
 

com-on-air_cs-linux/tools/coa_syncsniff.c

@@ -136,7 +136,7 @@ int main(int argc, char *argv[])
 	write_global_header(pcap);
 
 	//sniff-loop
-        while (0xDEC + 't')
+        while (0xDE + 't')
 	{
 		struct sniffed_packet buf;
 	        while (sizeof(struct sniffed_packet) == (ret = read(d, &buf, (sizeof(struct sniffed_packet)))))

com-on-air_cs-linux/tools/dect_cli.c

@@ -1001,7 +1001,7 @@ void mainloop(void)
 
 	int ret;
 
-	while (0xDEC + 'T')
+	while (0xDE + 'T')
 	{
 		tv.tv_sec  = 1;
 		tv.tv_usec = 0;

com-on-air_cs-linux/tools/dectshark/Makefile

@@ -1,6 +1,6 @@
 CPPFLAGS=-Wall -O2 -I../..
 dectshark: dectshark.o gui.o foundinfo.o scanmode_gui.o syncmode_gui.o packetparser.o packetsaver.o
-	g++ $(CPPFLAGS) dectshark.o gui.o scanmode_gui.o syncmode_gui.o foundinfo.o packetparser.o packetsaver.o -o dectshark -lcurses -lpthread -lpcap
+	g++ $(CPPFLAGS) dectshark.o gui.o scanmode_gui.o syncmode_gui.o foundinfo.o packetparser.o packetsaver.o -o dectshark -lncursesw -lpthread -lpcap
 
 clean:
 	rm *.o *~ dectshark

com-on-air_cs-linux/tools/dectshark/scanmode_gui.cpp

@@ -259,7 +259,7 @@ void *scanthread(void *threadid)
 	}
 
 
-	while(0xDEC + 'T')		// ;)
+	while(0xDE + 'T')		// ;)
 	{
 		dect_found found;
 		

com-on-air_cs-linux/tools/dectshark/syncmode_gui.cpp

@@ -263,7 +263,7 @@ void *syncthread(void *threadid)
 
 	psaver.openfilerfpi(RFPI);
 
-	while (0xDEC + 'T')
+	while (0xDE + 'T')
 	{
 		tv.tv_sec  = 1;
 		tv.tv_usec = 0;

com-on-air_cs-linux/tools/pcapstein.c

@@ -171,7 +171,7 @@ void play()
 		fprintf(stderr, "pcap error: %s\n", errbuf);
 }
 
-void shutdown()
+void _shutdown()
 {
 	pcap_close(fi.p);
 	close(fi.fpp);
@@ -187,6 +187,6 @@ int main(int argc, char ** argv)
 	}
 	init(argv[1]);
 	play();
-	shutdown();
+	_shutdown();
 	return 0;
 }