pwm: Ensure pwm_apply_state() doesn't modify the state argument

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: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
index e8385c1cf342..9145f6160649 100644
--- a/drivers/pwm/pwm-imx-tpm.c
+++ b/drivers/pwm/pwm-imx-tpm.c
@@ -89,7 +89,7 @@ to_imx_tpm_pwm_chip(struct pwm_chip *chip)
 static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
                                    struct imx_tpm_pwm_param *p,
                                    struct pwm_state *real_state,
-                                   struct pwm_state *state)
+                                   const struct pwm_state *state)
 {
         struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
         u32 rate, prescale, period_count, clock_unit;
@@ -289,7 +289,7 @@ static int pwm_imx_tpm_apply_hw(struct pwm_chip *chip,
 
 static int pwm_imx_tpm_apply(struct pwm_chip *chip,
                              struct pwm_device *pwm,
-                             struct pwm_state *state)
+                             const struct pwm_state *state)
 {
         struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
         struct imx_tpm_pwm_param param;