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From: "Uwe Kleine-König" <u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
To: Thierry Reding
	<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
Cc: linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org,
	linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: [PATCH 2/2] pwm: ensure pwm_apply_state() doesn't modify the state argument
Date: Tue, 12 Mar 2019 09:35:37 +0100	[thread overview]
Message-ID: <20190312083537.23748-3-u.kleine-koenig@pengutronix.de> (raw)
In-Reply-To: <20190312083537.23748-1-u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>

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>
---
 drivers/pwm/core.c            |  2 +-
 drivers/pwm/pwm-atmel-hlcdc.c |  2 +-
 drivers/pwm/pwm-atmel.c       |  2 +-
 drivers/pwm/pwm-bcm-iproc.c   |  2 +-
 drivers/pwm/pwm-cros-ec.c     |  2 +-
 drivers/pwm/pwm-hibvt.c       |  2 +-
 drivers/pwm/pwm-imx27.c       |  2 +-
 drivers/pwm/pwm-lpss.c        |  2 +-
 drivers/pwm/pwm-meson.c       |  2 +-
 drivers/pwm/pwm-rcar.c        |  2 +-
 drivers/pwm/pwm-rockchip.c    |  4 ++--
 drivers/pwm/pwm-stm32-lp.c    |  2 +-
 drivers/pwm/pwm-sun4i.c       | 10 ++--------
 drivers/pwm/pwm-zx.c          |  2 +-
 include/linux/pwm.h           |  4 ++--
 15 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 3149204567f3..e547c3217fca 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -464,7 +464,7 @@ EXPORT_SYMBOL_GPL(pwm_free);
  *	   if the requested config is not achievable, for example,
  *	   ->duty_cycle and ->period might be approximated.
  */
-int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
+int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
 {
 	int err;
 
diff --git a/drivers/pwm/pwm-atmel-hlcdc.c b/drivers/pwm/pwm-atmel-hlcdc.c
index 54c6633d9b5d..20f3feb6ce4a 100644
--- a/drivers/pwm/pwm-atmel-hlcdc.c
+++ b/drivers/pwm/pwm-atmel-hlcdc.c
@@ -50,7 +50,7 @@ static inline struct atmel_hlcdc_pwm *to_atmel_hlcdc_pwm(struct pwm_chip *chip)
 }
 
 static int atmel_hlcdc_pwm_apply(struct pwm_chip *c, struct pwm_device *pwm,
-				 struct pwm_state *state)
+				 const struct pwm_state *state)
 {
 	struct atmel_hlcdc_pwm *chip = to_atmel_hlcdc_pwm(c);
 	struct atmel_hlcdc *hlcdc = chip->hlcdc;
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index a9fd6f0d408c..c185d3d73d4e 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -210,7 +210,7 @@ static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
 }
 
 static int atmel_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			   struct pwm_state *state)
+			   const struct pwm_state *state)
 {
 	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 	struct pwm_state cstate;
diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
index d961a8207b1c..56c38cfae92c 100644
--- a/drivers/pwm/pwm-bcm-iproc.c
+++ b/drivers/pwm/pwm-bcm-iproc.c
@@ -115,7 +115,7 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 }
 
 static int iproc_pwmc_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			    struct pwm_state *state)
+			    const struct pwm_state *state)
 {
 	unsigned long prescale = IPROC_PWM_PRESCALE_MIN;
 	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c
index 98f6ac6cf6ab..db5faa79c33f 100644
--- a/drivers/pwm/pwm-cros-ec.c
+++ b/drivers/pwm/pwm-cros-ec.c
@@ -93,7 +93,7 @@ static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
 }
 
 static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			     struct pwm_state *state)
+			     const struct pwm_state *state)
 {
 	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
 	int duty_cycle;
diff --git a/drivers/pwm/pwm-hibvt.c b/drivers/pwm/pwm-hibvt.c
index a0b09603d13d..086dfd3850e8 100644
--- a/drivers/pwm/pwm-hibvt.c
+++ b/drivers/pwm/pwm-hibvt.c
@@ -161,7 +161,7 @@ static void hibvt_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 }
 
 static int hibvt_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-				struct pwm_state *state)
+			   const struct pwm_state *state)
 {
 	struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
 
diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index 806130654211..eefc69133fa4 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -205,7 +205,7 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
 }
 
 static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			   struct pwm_state *state)
+			   const struct pwm_state *state)
 {
 	unsigned long period_cycles, duty_cycles, prescale;
 	struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 2ac3a2aa9e53..3b7e7ee0da8c 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -125,7 +125,7 @@ static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
 }
 
 static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			  struct pwm_state *state)
+			  const struct pwm_state *state)
 {
 	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
 	int ret;
diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
index c1ed641b3e26..72def8772593 100644
--- a/drivers/pwm/pwm-meson.c
+++ b/drivers/pwm/pwm-meson.c
@@ -292,7 +292,7 @@ static void meson_pwm_disable(struct meson_pwm *meson, unsigned int id)
 }
 
 static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			   struct pwm_state *state)
+			   const struct pwm_state *state)
 {
 	struct meson_pwm_channel *channel = pwm_get_chip_data(pwm);
 	struct meson_pwm *meson = to_meson_pwm(chip);
diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index cfe7dd1b448e..91ab1889eb66 100644
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -158,7 +158,7 @@ static void rcar_pwm_disable(struct rcar_pwm_chip *rp)
 }
 
 static int rcar_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			  struct pwm_state *state)
+			  const struct pwm_state *state)
 {
 	struct rcar_pwm_chip *rp = to_rcar_pwm_chip(chip);
 	struct pwm_state cur_state;
diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 16186bcd99e0..1501541d801e 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -102,7 +102,7 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 }
 
 static void rockchip_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			       struct pwm_state *state)
+			       const struct pwm_state *state)
 {
 	struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
 	unsigned long period, duty;
@@ -186,7 +186,7 @@ static int rockchip_pwm_enable(struct pwm_chip *chip,
 }
 
 static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			      struct pwm_state *state)
+			      const struct pwm_state *state)
 {
 	struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
 	struct pwm_state curstate;
diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c
index 0059b24cfdc3..11c5295c6a86 100644
--- a/drivers/pwm/pwm-stm32-lp.c
+++ b/drivers/pwm/pwm-stm32-lp.c
@@ -31,7 +31,7 @@ static inline struct stm32_pwm_lp *to_stm32_pwm_lp(struct pwm_chip *chip)
 #define STM32_LPTIM_MAX_PRESCALER	128
 
 static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			      struct pwm_state *state)
+			      const struct pwm_state *state)
 {
 	struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip);
 	unsigned long long prd, div, dty;
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 470d4f71e7eb..52dace9f739e 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -146,7 +146,7 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,
 }
 
 static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
-			       struct pwm_state *state,
+			       const struct pwm_state *state,
 			       u32 *dty, u32 *prd, unsigned int *prsclr)
 {
 	u64 clk_rate, div = 0;
@@ -193,17 +193,11 @@ static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
 	*dty = div;
 	*prsclr = prescaler;
 
-	div = (u64)pval * NSEC_PER_SEC * *prd;
-	state->period = DIV_ROUND_CLOSEST_ULL(div, clk_rate);
-
-	div = (u64)pval * NSEC_PER_SEC * *dty;
-	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(div, clk_rate);
-
 	return 0;
 }
 
 static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			   struct pwm_state *state)
+			   const struct pwm_state *state)
 {
 	struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
 	struct pwm_state cstate;
diff --git a/drivers/pwm/pwm-zx.c b/drivers/pwm/pwm-zx.c
index 5d27c16edfb1..d6da939a2e57 100644
--- a/drivers/pwm/pwm-zx.c
+++ b/drivers/pwm/pwm-zx.c
@@ -151,7 +151,7 @@ static int zx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 }
 
 static int zx_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			struct pwm_state *state)
+			const struct pwm_state *state)
 {
 	struct zx_pwm_chip *zpc = to_zx_pwm_chip(chip);
 	struct pwm_state cstate;
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index b628abfffacc..7525787985bb 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -262,7 +262,7 @@ struct pwm_ops {
 	int (*capture)(struct pwm_chip *chip, struct pwm_device *pwm,
 		       struct pwm_capture *result, unsigned long timeout);
 	int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
-		     struct pwm_state *state);
+		     const struct pwm_state *state);
 	void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
 			  struct pwm_state *state);
 	struct module *owner;
@@ -316,7 +316,7 @@ struct pwm_capture {
 /* PWM user APIs */
 struct pwm_device *pwm_request(int pwm_id, const char *label);
 void pwm_free(struct pwm_device *pwm);
-int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
+int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state);
 int pwm_adjust_config(struct pwm_device *pwm);
 
 /**
-- 
2.20.1


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  parent reply	other threads:[~2019-03-12  8:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-12  8:35 [PATCH 0/2] pwm: ensure pwm_apply_state() doesn't modify the state argument Uwe Kleine-König
     [not found] ` <20190312083537.23748-1-u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2019-03-12  8:35   ` [PATCH 1/2] pwm: rockchip: Don't update the state for the caller of pwm_apply_state() Uwe Kleine-König
2019-03-12  8:35   ` Uwe Kleine-König [this message]
     [not found]     ` <20190312083537.23748-3-u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2019-03-12 11:42       ` [PATCH 2/2] pwm: ensure pwm_apply_state() doesn't modify the state argument Thierry Reding
2019-03-12 12:59         ` Uwe Kleine-König

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