Add mono invert and cutoff as parameters

Makefile

@@ -1,4 +1,5 @@
 obj-m += sharp.o
+sharp-objs += main.o params_iface.o
 
 export KROOT=/lib/modules/$(shell uname -r)/build
 

main.c

@@ -29,6 +29,8 @@
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_simple_kms_helper.h>
 
+#include "params_iface.h"
+
 #define GPIO_DISP 22
 #define GPIO_SCS 8
 #define GPIO_VCOM 23
@@ -148,11 +150,16 @@ static size_t sharp_memory_gray8_to_mono_tagged(u8 *buf, int width, int height,
 			for (b1 = 0; b1 < 8; b1++) {
 
 				// Change at what gray level the mono pixel is active here
-				if (buf[(line * width) + b8 + b1] >= 32) {
+				if (buf[(line * width) + b8 + b1] >= g_param_mono_cutoff) {
 					d |= 0b10000000 >> b1;
 				}
 			}
 
+			// Apply inversion
+			if (g_param_mono_invert) {
+				d = ~d;
+			}
+
 			// Without the line number and trailer tags, each destination
 			// mono line would have a length `width / 8`. However, we are
 			// inserting the line number at the beginning of the line and

params_iface.c

@@ -0,0 +1,32 @@
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+#include "params_iface.h"
+
+int g_param_mono_cutoff = 32;
+int g_param_mono_invert = 0;
+
+static int set_param_u8(const char *val, const struct kernel_param *kp)
+{
+	int rc, result;
+
+	// Parse string value
+	if ((rc = kstrtoint(val, 10, &result)) || (result < 0) || (result > 0xff)) {
+		return -EINVAL;
+	}
+
+	return param_set_int(val, kp);
+}
+
+static const struct kernel_param_ops u8_param_ops = {
+	.set = set_param_u8,
+	.get = param_get_int,
+};
+
+module_param_cb(mono_cutoff, &u8_param_ops, &g_param_mono_cutoff, 0660);
+MODULE_PARM_DESC(mono_cutoff,
+	"Greyscale value from 0-255 after which a mono pixel will be activated");
+
+module_param_cb(mono_invert, &u8_param_ops, &g_param_mono_invert, 0660);
+MODULE_PARM_DESC(mono_invert, "0 for no inversion, 1 for inversion");

params_iface.h

@@ -0,0 +1,7 @@
+#ifndef PARAMS_IFACE_H_
+#define PARAMS_IFACE_H_
+
+extern int g_param_mono_cutoff;
+extern int g_param_mono_invert;
+
+#endif