am7xxx: make sure am7xxx_get_device_info() always returns sensible values

am7xxx_get_device_info() was not covering the case of a non-NULL output
parameter on the very first invocation, this case would not usually
happen in normal operation, but the problem was there: in that case the
output device_info structure would have contained garbage, as spotted by
the static analyzer:

.../src/am7xxx.c:1279:21: warning: The right operand of '<=' is a garbage value
            original_width <= device_info.native_width &&
                           ^  ~~~~~~~~~~~~~~~~~~~~~~~~
.../src/am7xxx.c:1288:39: warning: The right operand of '/' is a garbage value
        width_ratio =  (float)original_width / device_info.native_width;
                                             ^ ~~~~~~~~~~~~~~~~~~~~~~~~

While at it also fix the symmetric case of a NULL output parameter on
subsequent invocation: check that the output argument is non-NULL before
memcpy-ing to it.

diff --git a/src/am7xxx.c b/src/am7xxx.c
index 2d7b890..512cf6f 100644 (file)
--- a/src/am7xxx.c
+++ b/src/am7xxx.c
@@ -1213,10 +1213,9 @@ AM7XXX_PUBLIC int am7xxx_get_device_info(am7xxx_device *dev,
        int ret;
        struct am7xxx_header h;
 
-       if (dev->device_info) {
-               memcpy(device_info, dev->device_info, sizeof(*device_info));
-               return 0;
-       }
+       /* if there is a cached copy of the device info, just return that */
+       if (dev->device_info)
+               goto return_value;
 
        ret = send_command(dev, AM7XXX_PACKET_TYPE_DEVINFO);
        if (ret < 0)
@@ -1250,6 +1249,9 @@ AM7XXX_PUBLIC int am7xxx_get_device_info(am7xxx_device *dev,
        dev->device_info->unknown1 = h.header_data.devinfo.unknown1;
 #endif
 
+return_value:
+       if (device_info)
+               memcpy(device_info, dev->device_info, sizeof(*device_info));
        return 0;
 }