[PATCH 14/14] pwm: Soften potential loss of precision in compat code

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

The legacy callback .config() only uses int for period and duty_cycle
while the corresponding values in struct pwm_state are u64. To prevent
that a value bigger than INT_MAX is discarded to a very small value,
explicitly check for big values and pass INT_MAX instead of discarding.

Acked-by: Guru Das Srinagesh <gurus@codeaurora.org>
Link: https://lore.kernel.org/r/20210315080050.2337075-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/pwm/core.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 4b3779d58c5a..b1adf3bb8508 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -605,9 +605,18 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
 
 		if (state->period != pwm->state.period ||
 		    state->duty_cycle != pwm->state.duty_cycle) {
+			int duty_cycle, period;
+
+			/*
+			 * The legacy callbacks use only (signed!) int for
+			 * period and duty_cycle compared to u64 in struct
+			 * pwm_state. So clamp the values to INT_MAX.
+			 */
+			period = min(state->period, (u64)INT_MAX);
+			duty_cycle = min(state->duty_cycle, (u64)INT_MAX);
+
 			err = chip->ops->config(pwm->chip, pwm,
-						state->duty_cycle,
-						state->period);
+						duty_cycle, period);
 			if (err)
 				return err;
 
-- 
2.30.1