tempd: Use uncached data on retry

If data read is retried due to error 85, we must read an uncached
value to prevent pulling the same error back from the cache.

Signed-off-by: Timo Kokkonen <timo.t.kokkonen@iki.fi>

diff --git a/tempd.c b/tempd.c
index 5120b00b6d0de4bc6a5a843efff9168699c546a0..56905e251e6b06be9bae8b4330047f170b0e6f47 100644 (file)
--- a/tempd.c
+++ b/tempd.c
@@ -15,12 +15,24 @@
 #define min(a, b) ((a) < (b) ? (a) : (b))
 #define max(a, b) ((a) > (b) ? (a) : (b))
 
-static int read_1wire_temp(const char *path, double *temp)
+static inline char *_strlcat(char *dst, const char *src, size_t len)
 {
+       strncat(dst, src, len - strnlen(dst, len) - 1);
+       dst[len - 1] = '\0';
+
+       return dst;
+}
+
+static int read_1wire_temp(const char *_path, double *temp)
+{
+       char uncached[512];
        char buf[16];
        int fd;
        int ret;
        int retries = 0;
+       const char *path = _path;
+       char *c;
+       int len;
 
 retry:
        fd = open(path, O_RDONLY);
@@ -44,16 +56,32 @@ retry:
 out_close:
        close(fd);
 
-       if (*temp == 85) {
-               ret = -1;
-               if (retries < 3) {
-                       retries++;
-                       printf("Retrying 1wire read, try %d\n", retries);
-                       goto retry;
-               }
+       if (*temp != 85 || retries >= 3)
+               return ret;
+
+       ret = -1;
+       retries++;
+       printf("Retrying 1wire read, try %d\n", retries);
+
+       if (retries > 1)
+               goto retry;
+
+       /* Make an uncached path first */
+       c = strstr(_path, "/28.");
+       if (!c)
+               c = strstr(_path, "/10.");
+       if (!c) {
+               printf("Unable to make uncached path of \"%s\", will not retry\n", _path);
+               return -1;
        }
 
-       return ret;
+       len = c - _path;
+       strncpy(uncached, _path, len);
+       uncached[len] = '\0';
+       _strlcat(uncached, "/uncached/", sizeof(uncached));
+       _strlcat(uncached, c, sizeof(uncached));
+       path = uncached;
+       goto retry;
 }
 
 struct data_entry {