[RFC PATCH 3/5] gpio: gpiolib: Add chardev support for maintaining GPIO values on reset

Andrew Jeffery
2017-10-20T03:37:25Z

Similar to devicetree support, add flags and mappings to expose reset
tolerance configuration through the chardev interface.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
drivers/gpio/gpiolib.c | 14 +++++++++++++-
include/uapi/linux/gpio.h | 11 ++++++-----
2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6b4c5df10e84..442ee5ceee08 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -357,7 +357,8 @@ struct linehandle_state {
GPIOHANDLE_REQUEST_OUTPUT | \
GPIOHANDLE_REQUEST_ACTIVE_LOW | \
GPIOHANDLE_REQUEST_OPEN_DRAIN | \
- GPIOHANDLE_REQUEST_OPEN_SOURCE)
+ GPIOHANDLE_REQUEST_OPEN_SOURCE | \
+ GPIOHANDLE_REQUEST_RESET_TOLERANT)

static long linehandle_ioctl(struct file *filep, unsigned int cmd,
unsigned long arg)
@@ -498,6 +499,17 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
set_bit(FLAG_OPEN_SOURCE, &desc->flags);

/*
+ * Unconditionally configure reset tolerance, as it's possible
+ * that the tolerance flag itself becomes tolerant to resets.
+ * Thus it could remain set from a previous environment, but
+ * the current environment may not expect it so.
+ */
+ ret = gpiod_set_reset_tolerant(desc,
+ !!(lflags & GPIOHANDLE_REQUEST_RESET_TOLERANT));
+ if (ret < 0)
+ goto out_free_descs;
+
+ /*
* Lines have to be requested explicitly for input
* or output, else the line will be treated "as is".
*/
diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
index 333d3544c964..1b1ce1af8653 100644
--- a/include/uapi/linux/gpio.h
+++ b/include/uapi/linux/gpio.h
@@ -56,11 +56,12 @@ struct gpioline_info {
#define GPIOHANDLES_MAX 64

/* Linerequest flags */
-#define GPIOHANDLE_REQUEST_INPUT (1UL << 0)
-#define GPIOHANDLE_REQUEST_OUTPUT (1UL << 1)
-#define GPIOHANDLE_REQUEST_ACTIVE_LOW (1UL << 2)
-#define GPIOHANDLE_REQUEST_OPEN_DRAIN (1UL << 3)
-#define GPIOHANDLE_REQUEST_OPEN_SOURCE (1UL << 4)
+#define GPIOHANDLE_REQUEST_INPUT (1UL << 0)
+#define GPIOHANDLE_REQUEST_OUTPUT (1UL << 1)
+#define GPIOHANDLE_REQUEST_ACTIVE_LOW (1UL << 2)
+#define GPIOHANDLE_REQUEST_OPEN_DRAIN (1UL << 3)
+#define GPIOHANDLE_REQUEST_OPEN_SOURCE (1UL << 4)
+#define GPIOHANDLE_REQUEST_RESET_TOLERANT (1UL << 5)

/**
* struct gpiohandle_request - Information about a GPIO handle request
--
2.11.0