[PATCH v2] iwd: Use same signal strength calculation as wpa_supplicant

[Jonathan Liu <net147@gmail.com>]

Fixes the signal strength reported by connman being lower when using iwd
compared to wpa_supplicant.

In the wifi plugin for wpa_supplicant, the signal strength is calculated
as follows:
strength = 120 + g_supplicant_network_get_signal(supplicant_network);
if (strength > 100)
    strength = 100;

The g_supplicant_network_get_signal() function returns the signal
strength in dBm. This means the signal strength calculation in connman
for wpa_supplicant treats -20 dBm or higher as 100% signal strength.

The iwd plugin is changed to use the same calculation but as iwd returns
returns the signal strength as 100 * dBm, it needs to be divided by 100
to get the same dBm value as wpa_supplicant.
---
 plugins/iwd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/plugins/iwd.c b/plugins/iwd.c
index ac3d1e17..2a245fe2 100644
--- a/plugins/iwd.c
+++ b/plugins/iwd.c
@@ -1128,7 +1128,9 @@ static unsigned char calculate_strength(int strength)
 	 * ConnMan expects it in the range from 100 (strongest) to 0
 	 * (weakest).
 	 */
-	res = (unsigned char)((strength + 10000) / 100);
+	res = (unsigned char)(120 + strength / 100);
+	if (res > 100)
+		res = 100;
 
 	return res;
 }
-- 
2.35.1