| Message ID | 20240409132126.1117916-2-ckeepax@opensource.cirrus.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add bridged amplifiers to cs42l43 | expand |
On Tue, Apr 9, 2024 at 3:21 PM Charles Keepax <ckeepax@opensource.cirrus.com> wrote: > 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. > > Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> I love it. Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Yours, Linus Walleij
On Tue, Apr 09, 2024 at 02:21:24PM +0100, Charles Keepax wrote: > 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_get_gpio_device() > swnode_gpio_undefined and return -ENOENT, which matches the behaviour > of the device tree system when it encounters a 0 phandle. ... > +config GPIO_SWNODE_UNDEFINED > + bool "Undefined swnode GPIOs" Why is this user visible? > + 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. How are drivers supposed to work in case this is not selected? ... > +EXPORT_SYMBOL_NS_GPL(swnode_gpio_undefined, GPIO_SWNODE); + export.h > +static int __init swnode_gpio_init(void) + init.h > + pr_err("gpiolib: failed to register swnode: %d\n", ret); + printk.h
On Tue, Apr 09, 2024 at 09:03:30PM +0300, Andy Shevchenko wrote: > On Tue, Apr 09, 2024 at 02:21:24PM +0100, Charles Keepax wrote: > > 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_get_gpio_device() > sorry yeah will fix that up. > > swnode_gpio_undefined and return -ENOENT, which matches the behaviour > > of the device tree system when it encounters a 0 phandle. > > ... > > > +config GPIO_SWNODE_UNDEFINED > > + bool "Undefined swnode GPIOs" > > Why is this user visible? > Yeah a good shout no reason for it to be. > > + 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. > > How are drivers supposed to work in case this is not selected? > > ... Well they don't :-) Thanks, Charles
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index b50d0b470849..e9b977139674 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -103,6 +103,15 @@ config GPIO_REGMAP select REGMAP tristate +config GPIO_SWNODE_UNDEFINED + bool "Undefined swnode GPIOs" + 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 diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c index fa52bdb1a29a..57722d829c61 100644 --- a/drivers/gpio/gpiolib-swnode.c +++ b/drivers/gpio/gpiolib-swnode.c @@ -17,6 +17,8 @@ #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 +42,13 @@ static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode) if (!gdev_node || !gdev_node->name) return ERR_PTR(-EINVAL); + /* + * Check for special node that identifies undefined GPIOs, this is + * primarily used as a key for internal chip selects in SPI bindings. + */ + if (!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 +130,32 @@ 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("gpiolib: 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 diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index db2dfbae8edb..e685fac43398 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -12,6 +12,8 @@ struct fwnode_handle; struct gpio_array; struct gpio_desc; +struct software_node; + /** * struct gpio_descs - Struct containing an array of descriptors that can be * obtained using gpiod_get_array() @@ -54,6 +56,8 @@ enum gpiod_flags { GPIOD_OUT_HIGH_OPEN_DRAIN = GPIOD_OUT_HIGH | GPIOD_FLAGS_BIT_OPEN_DRAIN, }; +extern const struct software_node swnode_gpio_undefined; + #ifdef CONFIG_GPIOLIB /* Return the number of GPIOs associated with a device / function */
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. Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> --- Changes since v3: - Add Kconfig to make swnode conditionally built - Add define for swnode name - Add custom init and exit calls - Use export namespaces Thanks, Charles drivers/gpio/Kconfig | 9 +++++++++ drivers/gpio/gpiolib-swnode.c | 38 +++++++++++++++++++++++++++++++++++ include/linux/gpio/consumer.h | 4 ++++ 3 files changed, 51 insertions(+)