Only force new entropy once a minute when backgrounded

Make the poll-timeout one minute if the option --daemon is used.
This saves a lot og CPU-time.

software/README

@@ -73,7 +73,9 @@ Options are:
     --raw - do not whiten the output
     --multiplier <value> - write 256 bits * value for each 512 bits written to the Keccak sponge
     --no-output - do not write random output data
-    --daemon - run in the background. Output should be redirected to a file or the options should be used with --dev-random
+    --daemon - run in the background. Output should be redirected to a file or
+    the options should be used with --dev-random. To reduce CPU-usage addition
+    af entropy is only forced after a minute rather than a second.
     --pidfile <filename> - write the process ID to a file. If --daemon is used, it is the ID of the background process.
     --serial <serial> - use Infinite Noise TRNG/FT240 with the given serial number (see --list-devices)
     --list-devices - list available devices

software/infnoise.c

@@ -56,7 +56,7 @@ static void outputBytes(uint8_t *bytes, uint32_t length, uint32_t entropy, struc
             exit(1);
         }
     } else {
-        inmWaitForPoolToHaveRoom();
+        inmWaitForPoolToHaveRoom(opts);
         inmWriteEntropyToPool(bytes, length, entropy);
     }
 }

software/infnoise.h

@@ -54,7 +54,7 @@ void inmClearEntropyLevel(void);
 bool inmEntropyOnTarget(uint32_t entropy, uint32_t bits);
 void inmWriteEntropyStart(uint32_t bufLen, struct opt_struct *opts);
 void inmWriteEntropyToPool(uint8_t *bytes, uint32_t length, uint32_t entropy);
-void inmWaitForPoolToHaveRoom(void);
+void inmWaitForPoolToHaveRoom(struct opt_struct *opts);
 void inmDumpStats(void);
 void startDaemon(struct opt_struct *opts);
 bool isSuperUser(void);

software/writeentropy.c

@@ -61,7 +61,7 @@ void inmWriteEntropyStart(uint32_t bufLen, struct opt_struct* opts) {
 }
 
 // Block until either the entropy pool has room, or 1 second has passed.
-void inmWaitForPoolToHaveRoom(void) {
+void inmWaitForPoolToHaveRoom(struct opt_struct *opts) {
     int ent_count;
     struct pollfd pfd = {
         .fd = inmDevRandomFD,
@@ -72,6 +72,8 @@ void inmWaitForPoolToHaveRoom(void) {
         return;
     }
     timeout_msec = 1000u; // One second
+    if (opts->daemon)
+	timeout_msec *= 60u; // Do not poll aggressively when in the background
     poll(&pfd, 1, timeout_msec);
 }