@@ -103,6 +103,15 @@ config GPIO_REGMAP
select REGMAP
tristate
+config GPIO_SWNODE_UNDEFINED
+ bool
+ help
+ This adds a special place holder for software nodes to contain an
+ undefined GPIO reference, this is primarily used by SPI to allow a
+ list of GPIO chip selects to mark a certain chip select as being
+ controlled the SPI device's internal chip select mechanism and not
+ a GPIO.
+
# put drivers in the right section, in alphabetical order
# This symbol is selected by both I2C and SPI expanders
@@ -4,8 +4,13 @@
*
* Copyright 2022 Google LLC
*/
+
+#define pr_fmt(fmt) "gpiolib: swnode: " fmt
+
#include <linux/err.h>
#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/property.h>
@@ -17,6 +22,8 @@
#include "gpiolib.h"
#include "gpiolib-swnode.h"
+#define GPIOLIB_SWNODE_UNDEFINED_NAME "swnode-gpio-undefined"
+
static void swnode_format_propname(const char *con_id, char *propname,
size_t max_size)
{
@@ -40,6 +47,14 @@ static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode)
if (!gdev_node || !gdev_node->name)
return ERR_PTR(-EINVAL);
+ /*
+ * Check for a special node that identifies undefined GPIOs, this is
+ * primarily used as a key for internal chip selects in SPI bindings.
+ */
+ if (IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED) &&
+ !strcmp(gdev_node->name, GPIOLIB_SWNODE_UNDEFINED_NAME))
+ return ERR_PTR(-ENOENT);
+
gdev = gpio_device_find_by_label(gdev_node->name);
return gdev ?: ERR_PTR(-EPROBE_DEFER);
}
@@ -121,3 +136,32 @@ int swnode_gpio_count(const struct fwnode_handle *fwnode, const char *con_id)
return count ?: -ENOENT;
}
+
+#if IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED)
+/*
+ * A special node that identifies undefined GPIOs, this is primarily used as
+ * a key for internal chip selects in SPI bindings.
+ */
+const struct software_node swnode_gpio_undefined = {
+ .name = GPIOLIB_SWNODE_UNDEFINED_NAME,
+};
+EXPORT_SYMBOL_NS_GPL(swnode_gpio_undefined, GPIO_SWNODE);
+
+static int __init swnode_gpio_init(void)
+{
+ int ret;
+
+ ret = software_node_register(&swnode_gpio_undefined);
+ if (ret < 0)
+ pr_err("failed to register swnode: %d\n", ret);
+
+ return ret;
+}
+subsys_initcall(swnode_gpio_init);
+
+static void __exit swnode_gpio_cleanup(void)
+{
+ software_node_unregister(&swnode_gpio_undefined);
+}
+__exitcall(swnode_gpio_cleanup);
+#endif
@@ -5,7 +5,11 @@
#include <dt-bindings/gpio/gpio.h> /* for GPIO_* flags */
#include <linux/property.h>
+struct software_node;
+
#define PROPERTY_ENTRY_GPIO(_name_, _chip_node_, _idx_, _flags_) \
PROPERTY_ENTRY_REF(_name_, _chip_node_, _idx_, _flags_)
+extern const struct software_node swnode_gpio_undefined;
+
#endif /* __LINUX_GPIO_PROPERTY_H */
SPI devices can specify a cs-gpios property to enumerate their chip selects. Under device tree, a zero entry in this property can be used to specify that a particular chip select is using the SPI controllers native chip select, for example: cs-gpios = <&gpio1 0 0>, <0>; Here, the second chip select is native. However, when using swnodes there is currently no way to specify a native chip select. The proposal here is to register a swnode_gpio_undefined software node, that can be specified to allow the indication of a native chip select. For example: static const struct software_node_ref_args device_cs_refs[] = { { .node = &device_gpiochip_swnode, .nargs = 2, .args = { 0, GPIO_ACTIVE_LOW }, }, { .node = &swnode_gpio_undefined, .nargs = 0, }, }; Register the swnode as the gpiolib is initialised and check in swnode_get_gpio_device() if the returned node matches swnode_gpio_undefined and return -ENOENT, which matches the behaviour of the device tree system when it encounters a 0 phandle. Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Andy Shevchenko <andy@kernel.org> Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> --- No changes since v6. Thanks, Charles drivers/gpio/Kconfig | 9 +++++++ drivers/gpio/gpiolib-swnode.c | 44 +++++++++++++++++++++++++++++++++++ include/linux/gpio/property.h | 4 ++++ 3 files changed, 57 insertions(+)