[Keyboard] Add support for jj4x4 numpad/macropad by Kprepublic (#5016)

* added keyboard jj4x4, a shorter version of the jj40

* removed useless file

* edited jj4x4 readme.md

* optimized array size in jj4x4 config.h, removed reference to jj40 layouts from rules.mk

* removed custom matrix for this ps2avrgb board, refactored column and row pins

2 files changed, 49 insertions, 0 deletions

diff --git a/keyboards/jj4x4/tools/README.md b/keyboards/jj4x4/tools/README.md
new file mode 100644
index 000000000..081984ed4
--- /dev/null
+++ b/keyboards/jj4x4/tools/README.md
@@ -0,0 +1,16 @@
+# JJ40 Tools
+
+## usb_detach.c
+
+When trying to flash on Linux, you may encounter a "Resource Unavailable" error. This means that Linux's HID driver has taken exclusive control of the keyboard, and the program script can't flash it.
+This program can force Linux to give up a device, so that the programming script can reset it.
+
+### To compile:
+```
+gcc usb_detach.c -o usb_detach
+```
+
+### To run:
+1. Use `lsusb` to discover the Bus and Device numbers for your keyboard.
+2. Run the program: `sudo ./usb_detach /dev/bus/usb/<BUS>/<DEVICE>`.
+3. Build and program the firmware as normal.
diff --git a/keyboards/jj4x4/tools/usb_detach.c b/keyboards/jj4x4/tools/usb_detach.c
new file mode 100644
index 000000000..c21e47a7a
--- /dev/null
+++ b/keyboards/jj4x4/tools/usb_detach.c
@@ -0,0 +1,33 @@
+/* Found at https://www.linuxquestions.org/questions/linux-hardware-18/how-to-unclaim-usb-device-558138/#post3406986 */
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <linux/ioctl.h>
+#include <linux/usbdevice_fs.h>
+
+int main(int argc, char**argv)
+{
+        struct usbdevfs_ioctl command;
+        int ret;
+        int fd;
+        int i;
+        if (argc>1) {
+                fd = open(argv[1],O_RDWR);
+                if (fd<1){
+                        perror("unable to open file");
+                        return 1;
+                }
+                for (i=0;i<255;i++){ // hack: should fetch how many interface there is.
+                        command.ifno = i;
+                        command.ioctl_code = USBDEVFS_DISCONNECT;
+                        command.data = NULL;
+                        ret = ioctl(fd, USBDEVFS_IOCTL, &command);
+                        if(ret!=-1)
+                                printf("un claimed interface %d %d\n",i,ret);
+                }
+        } else {
+                printf ("usage: %s /dev/bus/usb/BUS/DEVICE\n",argv[0]);
+                printf("Release all interfaces of this usb device for usage in virtualisation\n");
+        }
+}
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