first attempt i2c driver

6 files changed, 35 insertions, 155 deletions

diff --git a/driver/main.c b/driver/main.c
index 92ff9aa..2097edd 100644
--- a/driver/main.c
+++ b/driver/main.c
@@ -1,13 +1,9 @@
-// #include <linux/cdev.h>
 #include <linux/init.h>
-#include <linux/io.h>
-#include <linux/module.h>
-#include <linux/platform_device.h>
+#include <linux/i2c.h>
 
 #include "main.h"
 #include "platform.h"
 
-// struct cdev *cdev;
 struct device *dev;
 struct class *class;
 dev_t node = 0; // do not register /dev/lork
@@ -30,30 +26,14 @@ static int mod_init(void) {
 	}
 
 	// create platform driver
-	err = platform_driver_register(&lork_driver);
+	err = i2c_add_driver(&lork_driver);
 	if (err) goto free_platform_driver;
 
-	// create driver attribute under /sys/bus/platform/drivers/gpio-extern
-	err = driver_create_file(&lork_driver.driver, &drv_attr_int);
-	if (err) goto free_drv_attr_int;
-
-	// create device attributes under /sys/class
-	err = device_create_file(dev, &dev_attr_int);
-	if (err) goto free_dev_attr_int;
-	err = device_create_file(dev, &dev_attr_str);
-	if (err) goto free_dev_attr_str;
-
 	printk("%s() OK\n", __PRETTY_FUNCTION__);
 	return 0;
 
-free_dev_attr_str:
-	device_remove_file(dev, &dev_attr_str);
-free_dev_attr_int:
-	device_remove_file(dev, &dev_attr_int);
-free_drv_attr_int:
-	driver_remove_file(&lork_driver.driver, &drv_attr_int);
 free_platform_driver:
-	platform_driver_unregister(&lork_driver);
+	i2c_del_driver(&lork_driver);
 free_device:
 	device_destroy(class, node);
 free_class:
@@ -63,10 +43,7 @@ free_class:
 }
 
 static void mod_exit(void) {
-	device_remove_file(dev, &dev_attr_str);
-	device_remove_file(dev, &dev_attr_int);
-	driver_remove_file(&lork_driver.driver, &drv_attr_int);
-	platform_driver_unregister(&lork_driver);
+	i2c_del_driver(&lork_driver);
 	device_destroy(class, node);
 	class_destroy(class);
 	printk("%s()\n", __PRETTY_FUNCTION__);
diff --git a/driver/main.h b/driver/main.h
index a0ef924..666bcc1 100644
--- a/driver/main.h
+++ b/driver/main.h
@@ -5,18 +5,26 @@
 
 #include "platform.h"
 
-static const struct of_device_id lork_ids[] = {
-	{ .compatible = "gpio-extern" },
+static const struct of_device_id lork_match[] = {
+	{ .compatible = "lork-i2c" },
 	{},
 };
 
-struct platform_driver lork_driver = {
+static const struct i2c_device_id lork_ids[] = {
+	{ "foo", 0 },
+	{},
+};
+
+MODULE_DEVICE_TABLE(i2c, lork_ids);
+
+struct i2c_driver lork_driver = {
 	.probe = lork_probe,
 	.remove = lork_remove,
 	.driver = {
-		.name = "gpio-extern",
+		.name = "lork",
 		.owner = THIS_MODULE,
-		.of_match_table = of_match_ptr(lork_ids),
-	}
+		.of_match_table = of_match_ptr(lork_match),
+	},
+	.id_table = lork_ids,
 };
 
diff --git a/driver/platform.c b/driver/platform.c
index b177474..db82d14 100644
--- a/driver/platform.c
+++ b/driver/platform.c
@@ -1,85 +1,14 @@
 #include "platform.h"
 
+#include <linux/platform_device.h>
 #include <linux/types.h>
-#include <linux/of.h>
-#include <linux/of_address.h>
 
-// TODO: shouldn't these be used??
-// #include <linux/pinctrl/pinctrl.h>
-// #include <linux/gpio/driver.h>
-
-#include <dt-bindings/gpio/gpio.h>
-
-// NOTE: i believe any nonzero return value for the probe function is
-// recognized as an error because of
-// <https://github.com/torvalds/linux/blob/a5131c3fdf2608f1c15f3809e201cf540eb28489/drivers/base/platform.c#L1004>
-int lork_probe(struct platform_device* dev) {
-	// read gpios field from device tree
-	uint32_t dt_gpios[3];
-	of_property_read_u32_array(dev->dev.of_node, "gpios", dt_gpios, 3);
-
-	struct device_node* gpio1 = of_find_node_by_phandle(dt_gpios[0]);
-	uint32_t pin = dt_gpios[1];
-	uint32_t gpio_mode = dt_gpios[2];
-	printk("lork: configure pin %u w/ mode 0x%02x\n", pin, gpio_mode);
-
-	// find the multiplexer that controls pin
-	size_t len = of_property_count_u32_elems(gpio1, "gpio-ranges");
-	struct device_node* am33xx_pinmux = NULL;
-	for (size_t i = 0; i < len; i += 4) {
-		uint32_t phandle, pin_start, pin_offset, pin_size;
-		of_property_read_u32_index(gpio1, "gpio-ranges", i+0, &phandle);
-		of_property_read_u32_index(gpio1, "gpio-ranges", i+1, &pin_start);
-		of_property_read_u32_index(gpio1, "gpio-ranges", i+2, &pin_offset);
-		of_property_read_u32_index(gpio1, "gpio-ranges", i+3, &pin_size);
-
-		// get phandle for multiplexer corresponding to configured pin number
-		if (pin_start > pin || pin >= pin_start + pin_size) continue;
-
-		am33xx_pinmux = of_find_node_by_phandle(phandle);
-		printk("0x%02x, %u -> %u + %u\n", phandle, pin_start, pin_offset, pin_size);
-		break;
-	}
-	if (am33xx_pinmux == NULL) return EINVAL;
-
-	printk("%s(%s)\n", __PRETTY_FUNCTION__, dev->name);
+int lork_probe(struct i2c_client * client) {
+	printk(KERN_INFO "%s()\n", __PRETTY_FUNCTION__);
 	return 0;
 }
 
-int lork_remove(struct platform_device* dev) {
-	printk("%s(%s)\n", __PRETTY_FUNCTION__, dev->name);
-	return 0;
-}
-
-unsigned int val = 0;
-ssize_t drv_attr_int_show(struct device_driver* drv, char* buf) {
-	return sprintf(buf, "%u\n", val);
-}
-ssize_t drv_attr_int_store(struct device_driver* drv, const char* buf, size_t count) {
-	sscanf(buf, "%u", &val);
-	return count;
-}
-
-ssize_t dev_attr_int_show(struct device* dev, struct device_attribute* _attr, char* buf) {
-	return sprintf(buf, "%u\n", val);
-}
-ssize_t dev_attr_int_store(struct device* dev, struct device_attribute* _attr, const char* buf, size_t count) {
-	sscanf(buf, "%u", &val);
-	return count;
-}
-
-char* str = NULL;
-size_t str_len = 0;
-ssize_t dev_attr_str_show(struct device* dev, struct device_attribute* _attr, char* buf) {
-	if (str == NULL) return 0;
-	strncpy(buf, str, str_len);
-	return str_len;
-}
-ssize_t dev_attr_str_store(struct device* dev, struct device_attribute* _attr, const char* buf, size_t count) {
-	if (str != NULL) kfree(str);
-	str = kmalloc(count, 0);
-	str_len = count;
-	strncpy(str, buf, str_len);
-	return count;
+void lork_remove(struct i2c_client * client) {
+	return;
 }
 
diff --git a/driver/platform.h b/driver/platform.h
index ecac681..1173c3a 100644
--- a/driver/platform.h
+++ b/driver/platform.h
@@ -1,43 +1,8 @@
 #pragma once
 
-#include <linux/types.h>
 #include <linux/platform_device.h>
-#include <linux/slab.h>
+#include <linux/i2c.h>
 
-int lork_probe(struct platform_device*);
-int lork_remove(struct platform_device*);
-
-
-ssize_t drv_attr_int_show(struct device_driver*, char*);
-ssize_t drv_attr_int_store(struct device_driver*, const char*, size_t);
-static const struct driver_attribute drv_attr_int = {
-	.attr = {
-		.name = "int",
-		.mode = 0644,
-	},
-	.show = drv_attr_int_show,
-	.store = drv_attr_int_store,
-};
-
-ssize_t dev_attr_int_show(struct device*, struct device_attribute*, char*);
-ssize_t dev_attr_int_store(struct device*, struct device_attribute*, const char*, size_t);
-static const struct device_attribute dev_attr_int = {
-	.attr = {
-		.name = "int",
-		.mode = 0644,
-	},
-	.show = dev_attr_int_show,
-	.store = dev_attr_int_store,
-};
-
-ssize_t dev_attr_str_show(struct device*, struct device_attribute*, char*);
-ssize_t dev_attr_str_store(struct device*, struct device_attribute*, const char*, size_t);
-static const struct device_attribute dev_attr_str = {
-	.attr = {
-		.name = "str",
-		.mode = 0644,
-	},
-	.show = dev_attr_str_show,
-	.store = dev_attr_str_store,
-};
+int lork_probe(struct i2c_client *);
+void lork_remove(struct i2c_client *);
 
diff --git a/dts/am335x-boneblack-uboot.dts b/dts/am335x-boneblack-uboot.dts
index 43c1cfe..9cdeada 100644
--- a/dts/am335x-boneblack-uboot.dts
+++ b/dts/am335x-boneblack-uboot.dts
@@ -2177,7 +2177,7 @@
 					#size-cells = <0x01>;
 					ranges = <0x00 0x9c000 0x1000>;
 
-					i2c@0 {
+					i2c2: i2c@0 {
 						compatible = "ti,omap4-i2c";
 						#address-cells = <0x01>;
 						#size-cells = <0x00>;
@@ -2241,6 +2241,12 @@
 								phandle = <0xbb>;
 							};
 						};
+
+						// NOTE: this is in i2c2, so I2C2_SCL = P9.19 and I2C2_SDA = P9.20
+						lork {
+							compatible = "lork-i2c"; // load my driver
+							addr = <0x22>; // i2c slave address (see ../arduino/main.cpp)
+						};
 					};
 				};
 
@@ -3892,11 +3898,4 @@
 		not_available = "/not_available";
 		vmmcsd_fixed = "/fixedregulator0";
 	};
-
-	// this section is visible at runtime under
-	// /sys/firmware/devicetree/base/lork
-	lork {
-		compatible = "gpio-extern";
-		gpios = <&gpio1 18 GPIO_ACTIVE_HIGH>;
-	};
 };
diff --git a/readme.md b/readme.md
index ca989da..1db60b5 100644
--- a/readme.md
+++ b/readme.md
@@ -15,6 +15,7 @@
 - [Driver API][driver-api]
 - [AM335x Technical reference manual][ti-am335x-rm]
 - [BeagleBone Black system reference manual][bbb-srm]
+- [I2C device driver guide][linux-i2c]
 
 [kbuild-obj-var]: https://docs.kernel.org/kbuild/makefiles.html#loadable-module-goals-obj-m
 [kbuild-module-makefile]: https://www.kernel.org/doc/html/latest/kbuild/modules.html#creating-a-kbuild-file-for-an-external-module
@@ -25,6 +26,7 @@
 [driver-api]: https://www.kernel.org/doc/html/latest/driver-api/infrastructure.html
 [ti-am335x-rm]: https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf
 [bbb-srm]: https://cdn-shop.adafruit.com/datasheets/BBB_SRM.pdf
+[linux-i2c]: https://www.kernel.org/doc/html/latest/i2c/writing-clients.html
 
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