--- /dev/null
+From fc23ea48ba52c24f201fe5ca0132ee1a3de5a70a Mon Sep 17 00:00:00 2001
+From: Mauri Sandberg <maukka@ext.kapsi.fi>
+Date: Thu, 25 Mar 2021 11:48:05 +0200
+Subject: [PATCH 2/2] gpio: gpio-cascade: add generic GPIO cascade
+
+Adds support for building cascades of GPIO lines. That is, it allows
+setups when there is one upstream line and multiple cascaded lines, out
+of which one can be chosen at a time. The status of the upstream line
+can be conveyed to the selected cascaded line or, vice versa, the status
+of the cascaded line can be conveyed to the upstream line.
+
+A multiplexer is being used to select, which cascaded GPIO line is being
+used at any given time.
+
+At the moment only input direction is supported. In future it should be
+possible to add support for output direction, too.
+
+Signed-off-by: Mauri Sandberg <maukka@ext.kapsi.fi>
+Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
+Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
+---
+v7 -> v8:
+ - rearrange members in struct gpio_cascade
+ - cosmetic changes in file header and in one function declaration
+ - added Reviewed-by tags by Linus and Andy
+v6 -> v7:
+ - In Kconfig add info about module name
+ - adhere to new convention that allows lines longer than 80 chars
+ - use dev_probe_err with upstream gpio line too
+ - refactor for cleaner exit of probe function.
+v5 -> v6:
+ - In Kconfig, remove dependency to OF_GPIO and select only MULTIPLEXER
+ - refactor code preferring one-liners
+ - clean up prints, removing them from success-path.
+ - don't explicitly set gpio_chip.of_node as it's done in the GPIO library
+ - use devm_gpiochip_add_data instead of gpiochip_add
+v4 -> v5:
+ - renamed gpio-mux-input -> gpio-cascade. refactored code accordingly
+ here and there and changed to use new bindings and compatible string
+ - ambigious and vague 'pin' was rename to 'upstream_line'
+ - dropped Tested-by and Reviewed-by due to changes in bindings
+ - dropped Reported-by suggested by an automatic bot as it was not really
+ appropriate to begin with
+ - functionally it's the same as v4
+v3 -> v4:
+ - Changed author email
+ - Included Tested-by and Reviewed-by from Drew
+v2 -> v3:
+ - use managed device resources
+ - update Kconfig description
+v1 -> v2:
+ - removed .owner from platform_driver as per test bot's instruction
+ - added MODULE_AUTHOR, MODULE_DESCRIPTION, MODULE_LICENSE
+ - added gpio_mux_input_get_direction as it's recommended for all chips
+ - removed because this is input only chip: gpio_mux_input_set_value
+ - removed because they are not needed for input/output only chips:
+ gpio_mux_input_direction_input
+ gpio_mux_input_direction_output
+ - fixed typo in an error message
+ - added info message about successful registration
+ - removed can_sleep flag as this does not sleep while getting GPIO value
+ like I2C or SPI do
+ - Updated description in Kconfig
+---
+ drivers/gpio/Kconfig | 15 +++++
+ drivers/gpio/Makefile | 1 +
+ drivers/gpio/gpio-cascade.c | 117 ++++++++++++++++++++++++++++++++++++
+ 3 files changed, 133 insertions(+)
+ create mode 100644 drivers/gpio/gpio-cascade.c
+
+diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
+index 37a6f77c86fe..e69457144459 100644
+--- a/drivers/gpio/Kconfig
++++ b/drivers/gpio/Kconfig
+@@ -1694,4 +1694,19 @@ config GPIO_VIRTIO
+
+ endmenu
+
++comment "Other GPIO expanders"
++
++config GPIO_CASCADE
++ tristate "General GPIO cascade"
++ select MULTIPLEXER
++ help
++ Say yes here to enable support for generic GPIO cascade.
++
++ This allows building one-to-many cascades of GPIO lines using
++ different types of multiplexers readily available. At the
++ moment only input lines are supported.
++
++ To build the driver as a module choose 'm' and the resulting module
++ will be called 'gpio-cascade'.
++
+ endif
+diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
+index 71ee9fc2ff83..e8945456e7ea 100644
+--- a/drivers/gpio/Makefile
++++ b/drivers/gpio/Makefile
+@@ -45,6 +45,7 @@ obj-$(CONFIG_GPIO_BD9571MWV) += gpio-bd9571mwv.o
+ obj-$(CONFIG_GPIO_BRCMSTB) += gpio-brcmstb.o
+ obj-$(CONFIG_GPIO_BT8XX) += gpio-bt8xx.o
+ obj-$(CONFIG_GPIO_CADENCE) += gpio-cadence.o
++obj-$(CONFIG_GPIO_CASCADE) += gpio-cascade.o
+ obj-$(CONFIG_GPIO_CLPS711X) += gpio-clps711x.o
+ obj-$(CONFIG_GPIO_SNPS_CREG) += gpio-creg-snps.o
+ obj-$(CONFIG_GPIO_CRYSTAL_COVE) += gpio-crystalcove.o
+diff --git a/drivers/gpio/gpio-cascade.c b/drivers/gpio/gpio-cascade.c
+new file mode 100644
+index 000000000000..5cbda882d79a
+--- /dev/null
++++ b/drivers/gpio/gpio-cascade.c
+@@ -0,0 +1,117 @@
++// SPDX-License-Identifier: GPL-2.0-only
++/*
++ * A generic GPIO cascade driver
++ *
++ * Copyright (C) 2021 Mauri Sandberg <maukka@ext.kapsi.fi>
++ *
++ * This allows building cascades of GPIO lines in a manner illustrated
++ * below:
++ *
++ * /|---- Cascaded GPIO line 0
++ * Upstream | |---- Cascaded GPIO line 1
++ * GPIO line ----+ | .
++ * | | .
++ * \|---- Cascaded GPIO line n
++ *
++ * A multiplexer is being used to select, which cascaded line is being
++ * addressed at any given time.
++ *
++ * At the moment only input mode is supported due to lack of means for
++ * testing output functionality. At least theoretically output should be
++ * possible with open drain constructions.
++ */
++
++#include <linux/module.h>
++#include <linux/slab.h>
++#include <linux/platform_device.h>
++#include <linux/mux/consumer.h>
++
++#include <linux/gpio/consumer.h>
++#include <linux/gpio/driver.h>
++
++struct gpio_cascade {
++ struct gpio_chip gpio_chip;
++ struct device *parent;
++ struct mux_control *mux_control;
++ struct gpio_desc *upstream_line;
++};
++
++static struct gpio_cascade *chip_to_cascade(struct gpio_chip *gc)
++{
++ return container_of(gc, struct gpio_cascade, gpio_chip);
++}
++
++static int gpio_cascade_get_direction(struct gpio_chip *gc, unsigned int offset)
++{
++ return GPIO_LINE_DIRECTION_IN;
++}
++
++static int gpio_cascade_get_value(struct gpio_chip *gc, unsigned int offset)
++{
++ struct gpio_cascade *cas = chip_to_cascade(gc);
++ int ret;
++
++ ret = mux_control_select(cas->mux_control, offset);
++ if (ret)
++ return ret;
++
++ ret = gpiod_get_value(cas->upstream_line);
++ mux_control_deselect(cas->mux_control);
++ return ret;
++}
++
++static int gpio_cascade_probe(struct platform_device *pdev)
++{
++ struct device *dev = &pdev->dev;
++ struct gpio_cascade *cas;
++ struct mux_control *mc;
++ struct gpio_desc *upstream;
++ struct gpio_chip *gc;
++
++ cas = devm_kzalloc(dev, sizeof(*cas), GFP_KERNEL);
++ if (!cas)
++ return -ENOMEM;
++
++ mc = devm_mux_control_get(dev, NULL);
++ if (IS_ERR(mc))
++ return dev_err_probe(dev, PTR_ERR(mc), "unable to get mux-control\n");
++
++ cas->mux_control = mc;
++ upstream = devm_gpiod_get(dev, "upstream", GPIOD_IN);
++ if (IS_ERR(upstream))
++ return dev_err_probe(dev, PTR_ERR(upstream), "unable to claim upstream GPIO line\n");
++
++ cas->upstream_line = upstream;
++ cas->parent = dev;
++
++ gc = &cas->gpio_chip;
++ gc->get = gpio_cascade_get_value;
++ gc->get_direction = gpio_cascade_get_direction;
++ gc->base = -1;
++ gc->ngpio = mux_control_states(mc);
++ gc->label = dev_name(cas->parent);
++ gc->parent = cas->parent;
++ gc->owner = THIS_MODULE;
++
++ platform_set_drvdata(pdev, cas);
++ return devm_gpiochip_add_data(dev, &cas->gpio_chip, NULL);
++}
++
++static const struct of_device_id gpio_cascade_id[] = {
++ { .compatible = "gpio-cascade" },
++ { /* sentinel */ }
++};
++MODULE_DEVICE_TABLE(of, gpio_cascade_id);
++
++static struct platform_driver gpio_cascade_driver = {
++ .driver = {
++ .name = "gpio-cascade",
++ .of_match_table = gpio_cascade_id,
++ },
++ .probe = gpio_cascade_probe,
++};
++module_platform_driver(gpio_cascade_driver);
++
++MODULE_AUTHOR("Mauri Sandberg <maukka@ext.kapsi.fi>");
++MODULE_DESCRIPTION("Generic GPIO cascade");
++MODULE_LICENSE("GPL");
+--
+2.25.1
+
projects / openwrt / openwrt.git / commitdiff