• Uwe Kleine-König's avatar
    pwm: Ensure pwm_apply_state() doesn't modify the state argument · 71523d18
    Uwe Kleine-König authored
    It is surprising for a PWM consumer when the variable holding the
    requested state is modified by pwm_apply_state(). Consider for example a
    driver doing:
    
            #define PERIOD 5000000
            #define DUTY_LITTLE 10
            ...
            struct pwm_state state = {
                    .period = PERIOD,
                    .duty_cycle = DUTY_LITTLE,
                    .polarity = PWM_POLARITY_NORMAL,
                    .enabled = true,
            };
    
            pwm_apply_state(mypwm, &state);
            ...
            state.duty_cycle = PERIOD / 2;
            pwm_apply_state(mypwm, &state);
    
    For sure the second call to pwm_apply_state() should still have
    state.period = PERIOD and not something the hardware driver chose for a
    reason that doesn't necessarily apply to the second call.
    
    So declare the state argument as a pointer to a const type and adapt all
    drivers' .apply callbacks.
    Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
    Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
    71523d18
pwm-zx.c 6.46 KB