linux-kernel - [PATCH v3 1/3] gpio: gpio-regmap: add flags to control some behaviour

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250821101902.626329-2-marcos@orca.pet>
Date: Thu, 21 Aug 2025 12:18:57 +0200
From: Marcos Del Sol Vives <marcos@...a.pet>
To: linux-kernel@...r.kernel.org
Cc: Marcos Del Sol Vives <marcos@...a.pet>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Michael Walle <mwalle@...nel.org>,
	Lee Jones <lee@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-gpio@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: [PATCH v3 1/3] gpio: gpio-regmap: add flags to control some behaviour

The Vortex86 family of SoCs need the direction set before the value, else
writes to the DATA ports are ignored.

This commit adds a new "flags" field plus a flag to change the default
behaviour, which is to set first the direction and then the value.

Signed-off-by: Marcos Del Sol Vives <marcos@...a.pet>
---
 drivers/gpio/gpio-regmap.c  | 17 ++++++++++++++++-
 include/linux/gpio/regmap.h | 17 +++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index e8a32dfebdcb..24cefbd57637 100644
--- a/drivers/gpio/gpio-regmap.c
+++ b/drivers/gpio/gpio-regmap.c
@@ -31,6 +31,7 @@ struct gpio_regmap {
 	unsigned int reg_clr_base;
 	unsigned int reg_dir_in_base;
 	unsigned int reg_dir_out_base;
+	unsigned int flags;
 
 	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
 			      unsigned int offset, unsigned int *reg,
@@ -196,7 +197,20 @@ static int gpio_regmap_direction_input(struct gpio_chip *chip,
 static int gpio_regmap_direction_output(struct gpio_chip *chip,
 					unsigned int offset, int value)
 {
-	gpio_regmap_set(chip, offset, value);
+	struct gpio_regmap *gpio = gpiochip_get_data(chip);
+	int ret;
+
+	if (gpio->flags & GPIO_REGMAP_DIR_BEFORE_SET) {
+		ret = gpio_regmap_set_direction(chip, offset, true);
+		if (ret)
+			return ret;
+
+		return gpio_regmap_set(chip, offset, value);
+	}
+
+	ret = gpio_regmap_set(chip, offset, value);
+	if (ret)
+		return ret;
 
 	return gpio_regmap_set_direction(chip, offset, true);
 }
@@ -247,6 +261,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 	gpio->reg_clr_base = config->reg_clr_base;
 	gpio->reg_dir_in_base = config->reg_dir_in_base;
 	gpio->reg_dir_out_base = config->reg_dir_out_base;
+	gpio->flags = config->flags;
 
 	chip = &gpio->gpio_chip;
 	chip->parent = config->parent;
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index c722c67668c6..aea107e71fec 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -12,6 +12,20 @@ struct regmap;
 #define GPIO_REGMAP_ADDR_ZERO ((unsigned int)(-1))
 #define GPIO_REGMAP_ADDR(addr) ((addr) ? : GPIO_REGMAP_ADDR_ZERO)
 
+
+/**
+ * enum gpio_regmap_flags - flags to control GPIO operation
+ */
+enum gpio_regmap_flags {
+	/**
+	 * @GPIO_REGMAP_DIR_BEFORE_SET: when setting a pin as an output, set
+	 * its direction before the value. The output value will be undefined
+	 * for a short time which may have unwanted side effects, but some
+	 * hardware requires this.
+	 */
+	GPIO_REGMAP_DIR_BEFORE_SET	= BIT(0),
+};
+
 /**
  * struct gpio_regmap_config - Description of a generic regmap gpio_chip.
  * @parent:		The parent device
@@ -23,6 +37,8 @@ struct regmap;
  *			If not given, the name of the device is used.
  * @ngpio:		(Optional) Number of GPIOs
  * @names:		(Optional) Array of names for gpios
+ * @flags:		(Optional) A bitmask of flags from
+ * 			&enum gpio_regmap_flags
  * @reg_dat_base:	(Optional) (in) register base address
  * @reg_set_base:	(Optional) set register base address
  * @reg_clr_base:	(Optional) clear register base address
@@ -68,6 +84,7 @@ struct gpio_regmap_config {
 	const char *label;
 	int ngpio;
 	const char *const *names;
+	unsigned int flags;
 
 	unsigned int reg_dat_base;
 	unsigned int reg_set_base;
-- 
2.34.1