linux-kernel - [PATCH 3/5] gpio: cdev: update flags at once when reconfiguring from user-space

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Message-Id: <20241004-gpio-notify-in-kernel-events-v1-3-8ac29e1df4fe@linaro.org>
Date: Fri, 04 Oct 2024 16:43:24 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>, Kent Gibson <warthog618@...il.com>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 3/5] gpio: cdev: update flags at once when reconfiguring
 from user-space

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

Make updating the descriptor flags when reconfiguring from user-space
consistent with the rest of the codebase: read the current state
atomically, update it according to user's instructions and write it back
atomically as well.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/gpiolib-cdev.c | 70 +++++++++++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 31 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 6113a283c34a..b0050250ac3a 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -143,18 +143,22 @@ static int linehandle_validate_flags(u32 flags)
 
 static void linehandle_flags_to_desc_flags(u32 lflags, unsigned long *flagsp)
 {
-	assign_bit(FLAG_ACTIVE_LOW, flagsp,
+	unsigned long flags = READ_ONCE(*flagsp);
+
+	assign_bit(FLAG_ACTIVE_LOW, &flags,
 		   lflags & GPIOHANDLE_REQUEST_ACTIVE_LOW);
-	assign_bit(FLAG_OPEN_DRAIN, flagsp,
+	assign_bit(FLAG_OPEN_DRAIN, &flags,
 		   lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN);
-	assign_bit(FLAG_OPEN_SOURCE, flagsp,
+	assign_bit(FLAG_OPEN_SOURCE, &flags,
 		   lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE);
-	assign_bit(FLAG_PULL_UP, flagsp,
+	assign_bit(FLAG_PULL_UP, &flags,
 		   lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP);
-	assign_bit(FLAG_PULL_DOWN, flagsp,
+	assign_bit(FLAG_PULL_DOWN, &flags,
 		   lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN);
-	assign_bit(FLAG_BIAS_DISABLE, flagsp,
+	assign_bit(FLAG_BIAS_DISABLE, &flags,
 		   lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE);
+
+	WRITE_ONCE(*flagsp, flags);
 }
 
 static long linehandle_set_config(struct linehandle_state *lh,
@@ -1348,38 +1352,42 @@ static int gpio_v2_line_config_validate(struct gpio_v2_line_config *lc,
 	return 0;
 }
 
-static void gpio_v2_line_config_flags_to_desc_flags(u64 flags,
+static void gpio_v2_line_config_flags_to_desc_flags(u64 lflags,
 						    unsigned long *flagsp)
 {
-	assign_bit(FLAG_ACTIVE_LOW, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_ACTIVE_LOW);
+	unsigned long flags = READ_ONCE(*flagsp);
 
-	if (flags & GPIO_V2_LINE_FLAG_OUTPUT)
-		set_bit(FLAG_IS_OUT, flagsp);
-	else if (flags & GPIO_V2_LINE_FLAG_INPUT)
-		clear_bit(FLAG_IS_OUT, flagsp);
+	assign_bit(FLAG_ACTIVE_LOW, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_ACTIVE_LOW);
 
-	assign_bit(FLAG_EDGE_RISING, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_EDGE_RISING);
-	assign_bit(FLAG_EDGE_FALLING, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_EDGE_FALLING);
+	if (lflags & GPIO_V2_LINE_FLAG_OUTPUT)
+		set_bit(FLAG_IS_OUT, &flags);
+	else if (lflags & GPIO_V2_LINE_FLAG_INPUT)
+		clear_bit(FLAG_IS_OUT, &flags);
 
-	assign_bit(FLAG_OPEN_DRAIN, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_OPEN_DRAIN);
-	assign_bit(FLAG_OPEN_SOURCE, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_OPEN_SOURCE);
+	assign_bit(FLAG_EDGE_RISING, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_EDGE_RISING);
+	assign_bit(FLAG_EDGE_FALLING, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_EDGE_FALLING);
 
-	assign_bit(FLAG_PULL_UP, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP);
-	assign_bit(FLAG_PULL_DOWN, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN);
-	assign_bit(FLAG_BIAS_DISABLE, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_BIAS_DISABLED);
+	assign_bit(FLAG_OPEN_DRAIN, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_OPEN_DRAIN);
+	assign_bit(FLAG_OPEN_SOURCE, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_OPEN_SOURCE);
 
-	assign_bit(FLAG_EVENT_CLOCK_REALTIME, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME);
-	assign_bit(FLAG_EVENT_CLOCK_HTE, flagsp,
-		   flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE);
+	assign_bit(FLAG_PULL_UP, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP);
+	assign_bit(FLAG_PULL_DOWN, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN);
+	assign_bit(FLAG_BIAS_DISABLE, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_BIAS_DISABLED);
+
+	assign_bit(FLAG_EVENT_CLOCK_REALTIME, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME);
+	assign_bit(FLAG_EVENT_CLOCK_HTE, &flags,
+		   lflags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE);
+
+	WRITE_ONCE(*flagsp, flags);
 }
 
 static long linereq_get_values(struct linereq *lr, void __user *ip)

-- 
2.43.0