I just ran the static analyser cppcheck over the source code of the
linux kernel version 3.6-rc6.

It said

[linux-3.6-rc6/drivers/net/wireless/ath/ath5k/phy.c:1977]: (warning) Redundant assignment of "symbol_width" in switch

The source code is

        case AR5K_BWMODE_10MHZ:
            /* Both sample_freq and chip_freq are 20MHz (?) */
            spur_delta_phase = (spur_offset << 18) / 25;
            spur_freq_sigma_delta = (spur_delta_phase >> 10);
            symbol_width = AR5K_SPUR_SYMBOL_WIDTH_BASE_100Hz / 2;
        case AR5K_BWMODE_5MHZ:
            /* Both sample_freq and chip_freq are 10MHz (?) */
            spur_delta_phase = (spur_offset << 19) / 25;
            spur_freq_sigma_delta = (spur_delta_phase >> 10);
            symbol_width = AR5K_SPUR_SYMBOL_WIDTH_BASE_100Hz / 4;
        default:

I agree with cppcheck, I think there are some missing break statements
in these cases.