drivers/mux/gpio.c

   1 /*
   2  * GPIO-controlled multiplexer driver
   3  *
   4  * Copyright (C) 2017 Axentia Technologies AB
   5  *
   6  * Author: Peter Rosin <peda@axentia.se>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/err.h>
  14 #include <linux/gpio/consumer.h>
  15 #include <linux/module.h>
  16 #include <linux/mux/driver.h>
  17 #include <linux/of_platform.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/property.h>
  20
  21 struct mux_gpio {
  22         struct gpio_descs *gpios;
  23         int *val;
  24 };
  25
  26 static int mux_gpio_set(struct mux_control *mux, int state)
  27 {
  28         struct mux_gpio *mux_gpio = mux_chip_priv(mux->chip);
  29         int i;
  30
  31         for (i = 0; i < mux_gpio->gpios->ndescs; i++)
  32                 mux_gpio->val[i] = (state >> i) & 1;
  33
  34         gpiod_set_array_value_cansleep(mux_gpio->gpios->ndescs,
  35                                        mux_gpio->gpios->desc,
  36                                        mux_gpio->val);
  37
  38         return 0;
  39 }
  40
  41 static const struct mux_control_ops mux_gpio_ops = {
  42         .set = mux_gpio_set,
  43 };
  44
  45 static const struct of_device_id mux_gpio_dt_ids[] = {
  46         { .compatible = "gpio-mux", },
  47         { /* sentinel */ }
  48 };
  49 MODULE_DEVICE_TABLE(of, mux_gpio_dt_ids);
  50
  51 static int mux_gpio_probe(struct platform_device *pdev)
  52 {
  53         struct device *dev = &pdev->dev;
  54         struct mux_chip *mux_chip;
  55         struct mux_gpio *mux_gpio;
  56         int pins;
  57         s32 idle_state;
  58         int ret;
  59
  60         pins = gpiod_count(dev, "mux");
  61         if (pins < 0)
  62                 return pins;
  63
  64         mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*mux_gpio) +
  65                                        pins * sizeof(*mux_gpio->val));
  66         if (IS_ERR(mux_chip))
  67                 return PTR_ERR(mux_chip);
  68
  69         mux_gpio = mux_chip_priv(mux_chip);
  70         mux_gpio->val = (int *)(mux_gpio + 1);
  71         mux_chip->ops = &mux_gpio_ops;
  72
  73         mux_gpio->gpios = devm_gpiod_get_array(dev, "mux", GPIOD_OUT_LOW);
  74         if (IS_ERR(mux_gpio->gpios)) {
  75                 ret = PTR_ERR(mux_gpio->gpios);
  76                 if (ret != -EPROBE_DEFER)
  77                         dev_err(dev, "failed to get gpios\n");
  78                 return ret;
  79         }
  80         WARN_ON(pins != mux_gpio->gpios->ndescs);
  81         mux_chip->mux->states = 1 << pins;
  82
  83         ret = device_property_read_u32(dev, "idle-state", (u32 *)&idle_state);
  84         if (ret >= 0 && idle_state != MUX_IDLE_AS_IS) {
  85                 if (idle_state < 0 || idle_state >= mux_chip->mux->states) {
  86                         dev_err(dev, "invalid idle-state %u\n", idle_state);
  87                         return -EINVAL;
  88                 }
  89
  90                 mux_chip->mux->idle_state = idle_state;
  91         }
  92
  93         ret = devm_mux_chip_register(dev, mux_chip);
  94         if (ret < 0)
  95                 return ret;
  96
  97         dev_info(dev, "%u-way mux-controller registered\n",
  98                  mux_chip->mux->states);
  99
 100         return 0;
 101 }
 102
 103 static struct platform_driver mux_gpio_driver = {
 104         .driver = {
 105                 .name = "gpio-mux",
 106                 .of_match_table = of_match_ptr(mux_gpio_dt_ids),
 107         },
 108         .probe = mux_gpio_probe,
 109 };
 110 module_platform_driver(mux_gpio_driver);
 111
 112 MODULE_DESCRIPTION("GPIO-controlled multiplexer driver");
 113 MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
 114 MODULE_LICENSE("GPL v2");