rocker: fix Wmaybe-uninitialized false-positive

gcc-7 reports a warning that earlier versions did not have:

drivers/net/ethernet/rocker/rocker_ofdpa.c: In function 'ofdpa_port_stp_update':
arch/x86/include/asm/string_32.h:79:22: error: '*((void *)&prev_ctrls+4)' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   *((short *)to + 2) = *((short *)from + 2);
   ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/rocker/rocker_ofdpa.c:2218:7: note: '*((void *)&prev_ctrls+4)' was declared here

This is clearly a variation of the warning about 'prev_state' that
was shut up using uninitialized_var().

We can slightly simplify the code and get rid of the warning by unconditionally
saving the prev_state and prev_ctrls variables. The inlined memcpy is not
particularly expensive here, as it just has to read five bytes from one or
two cache lines.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/rocker/rocker_ofdpa.c b/drivers/net/ethernet/rocker/rocker_ofdpa.c
index 7cd76b6..2ae8524 100644 (file)
--- a/drivers/net/ethernet/rocker/rocker_ofdpa.c
+++ b/drivers/net/ethernet/rocker/rocker_ofdpa.c
@@ -2216,18 +2216,15 @@ static int ofdpa_port_stp_update(struct ofdpa_port *ofdpa_port,
 {
        bool want[OFDPA_CTRL_MAX] = { 0, };
        bool prev_ctrls[OFDPA_CTRL_MAX];
-       u8 uninitialized_var(prev_state);
+       u8 prev_state;
        int err;
        int i;
 
-       if (switchdev_trans_ph_prepare(trans)) {
-               memcpy(prev_ctrls, ofdpa_port->ctrls, sizeof(prev_ctrls));
-               prev_state = ofdpa_port->stp_state;
-       }
-
-       if (ofdpa_port->stp_state == state)
+       prev_state = ofdpa_port->stp_state;
+       if (prev_state == state)
                return 0;
 
+       memcpy(prev_ctrls, ofdpa_port->ctrls, sizeof(prev_ctrls));
        ofdpa_port->stp_state = state;
 
        switch (state) {