Use calibration for preview

src/dcp.c

@@ -1,8 +1,10 @@
 #include "dcp.h"
 
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 unsigned int
 get_int32(const unsigned char *buffer, size_t offset)
@@ -147,3 +149,63 @@ parse_calibration_file(const char *path)
 
         return result;
 }
+
+bool
+find_calibration_by_model(char *conffile, char *model, const char *sensor)
+{
+        // Check config/%model,%sensor.dcp in the current working directory
+        sprintf(conffile, "config/%s,%s.dcp", model, sensor);
+        if (access(conffile, F_OK) != -1) {
+                printf("Found calibration file at %s\n", conffile);
+                return true;
+        }
+
+        // Check user overridden /etc/megapixels/config/%model,%sensor.dcp
+        sprintf(conffile,
+                "%s/megapixels/config/%s,%s.dcp",
+                SYSCONFDIR,
+                model,
+                sensor);
+        if (access(conffile, F_OK) != -1) {
+                printf("Found calibration file at %s\n", conffile);
+                return true;
+        }
+
+        // Check packaged /usr/share/megapixels/config/%model,%sensor.ini
+        sprintf(conffile, "%s/megapixels/config/%s,%s.dcp", DATADIR, model, sensor);
+        if (access(conffile, F_OK) != -1) {
+                printf("Found calibration file at %s\n", conffile);
+                return true;
+        }
+        printf("No calibration found for %s,%s\n", model, sensor);
+        return false;
+}
+
+bool
+find_calibration(char *conffile, const char *sensor)
+{
+        char model[512];
+        FILE *fp;
+
+        if (access("/proc/device-tree/compatible", F_OK) == -1) {
+                return false;
+        }
+        fp = fopen("/proc/device-tree/compatible", "r");
+        char *modelptr = model;
+        while (1) {
+                int c = fgetc(fp);
+                if (c == EOF) {
+                        *(modelptr) = '\0';
+                        return find_calibration_by_model(conffile, model, sensor);
+                }
+                *(modelptr++) = (char)c;
+                if (c == 0) {
+                        bool res =
+                                find_calibration_by_model(conffile, model, sensor);
+                        if (res) {
+                                return true;
+                        }
+                        modelptr = model;
+                }
+        }
+}