[PATCH 1/2] hid-mcp2200 added driver for MCP2200 GPIOs

[Johannes Roith]

Added a gpiochip compatible driver to control the 8 GPIOs of the MCP2200
by using the HID interface.

Using GPIOs with alternative functions (GP0<->SSPND, GP1<->USBCFG,
GP6<->RXLED, GP7<->TXLED) will reset the functions, if set (unset by
default).

The driver was tested while also using the UART of the chip. Setting
and reading the GPIOs has no effect on the UART communication. However,
a reset is triggered after the CONFIGURE command. If the GPIO Direction
is constantly changed, this will affect the communication at low baud
rates. This is a hardware problem of the MCP2200 and is not caused by
the driver.

Signed-off-by: Johannes Roith <johannes@gnu-linux.rocks>

 create mode 100644 drivers/hid/hid-mcp2200.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 4ce012f83253..02115dcc6b0b 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1283,6 +1283,16 @@ config HID_MCP2221
 	To compile this driver as a module, choose M here: the module
 	will be called hid-mcp2221.ko.
 
+config HID_MCP2200
+	tristate "Microchip MCP2200 HID USB-to-GPIO bridge"
+	depends on USB_HID
+	imply GPIOLIB
+	help
+	Provides GPIO functionality over USB-HID through MCP2200 device.
+
+	To compile this driver as a module, choose M here: the module
+	will be called hid-mcp2200.ko.
+
 config HID_KUNIT_TEST
 	tristate "KUnit tests for HID" if !KUNIT_ALL_TESTS
 	depends on KUNIT=y
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index 5d37cacbde33..d593fb982f7d 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -79,6 +79,7 @@ obj-$(CONFIG_HID_MACALLY)	+= hid-macally.o
 obj-$(CONFIG_HID_MAGICMOUSE)	+= hid-magicmouse.o
 obj-$(CONFIG_HID_MALTRON)	+= hid-maltron.o
 obj-$(CONFIG_HID_MCP2221)	+= hid-mcp2221.o
+obj-$(CONFIG_HID_MCP2200)	+= hid-mcp2200.o
 obj-$(CONFIG_HID_MAYFLASH)	+= hid-mf.o
 obj-$(CONFIG_HID_MEGAWORLD_FF)	+= hid-megaworld.o
 obj-$(CONFIG_HID_MICROSOFT)	+= hid-microsoft.o
diff --git a/drivers/hid/hid-mcp2200.c b/drivers/hid/hid-mcp2200.c
new file mode 100644
index 000000000000..600f3f3e073b
--- /dev/null
+++ b/drivers/hid/hid-mcp2200.c
@@ -0,0 +1,421 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MCP2200 - Microchip USB to GPIO bridge
+ *
+ * Copyright (c) 2023, Johannes Roith <johannes@gnu-linux.rocks>
+ *
+ * Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/22228A.pdf
+ * App Note for HID: https://ww1.microchip.com/downloads/en/DeviceDoc/93066A.pdf
+ */
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/bitfield.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/hid.h>
+#include <linux/hidraw.h>
+#include <linux/gpio/driver.h>
+#include "hid-ids.h"
+
+/* Commands codes in a raw output report */
+enum {
+	SET_CLEAR_OUTPUTS = 0x08,
+	CONFIGURE = 0x10,
+	READ_EE = 0x20,
+	WRITE_EE = 0x40,
+	READ_ALL = 0x80
+};
+
+/* MCP GPIO direction encoding */
+enum MCP_IO_DIR {
+	MCP2200_DIR_OUT = 0x00,
+	MCP2200_DIR_IN  = 0x01,
+};
+
+/* Altternative pin assignments */
+enum {
+	TXLED = 2,
+	RXLED = 3,
+	USBCFG = 6,
+	SSPND = 7,
+
+};
+
+#define MCP_NGPIO 8
+
+/* CMD to set or clear a GPIO output */
+struct mcp_set_clear_outputs {
+	u8 cmd;
+	u8 dummys1[10];
+	u8 set_bmap;
+	u8 clear_bmap;
+	u8 dummys2[3];
+} __packed;
+
+/* CMD to configure the IOs */
+struct mcp_configure {
+	u8 cmd;
+	u8 dummys1[3];
+	u8 io_bmap;
+	u8 config_alt_pins;
+	u8 io_default_val_bmap;
+	u8 config_alt_options;
+	u8 baud_h;
+	u8 baud_l;
+	u8 dummys2[6];
+} __packed;
+
+/* CMD to read all parameters */
+struct mcp_read_all {
+	u8 cmd;
+	u8 dummys[15];
+} __packed;
+
+/* Response to the read all cmd */
+struct mcp_read_all_resp {
+	u8 cmd;
+	u8 eep_addr;
+	u8 dummy;
+	u8 eep_val;
+	u8 io_bmap;
+	u8 config_alt_pins;
+	u8 io_default_val_bmap;
+	u8 config_alt_options;
+	u8 baud_h;
+	u8 baud_l;
+	u8 io_port_val_bmap;
+	u8 dummys[5];
+} __packed;
+
+struct mcp2200 {
+	struct hid_device *hdev;
+	struct mutex lock;
+	struct completion wait_in_report;
+	u8 gpio_dir;
+	u8 gpio_val;
+	u8 gpio_inval;
+	u8 baud_h;
+	u8 baud_l;
+	u8 config_alt_pins;
+	u8 gpio_reset_val;
+	u8 config_alt_options;
+	int status;
+	struct gpio_chip gc;
+};
+
+/* this executes the READ_ALL cmd */
+static int mcp_cmd_read_all(struct mcp2200 *mcp)
+{
+	struct mcp_read_all *read_all;
+	int len, t;
+
+	reinit_completion(&mcp->wait_in_report);
+	mutex_lock(&mcp->lock);
+
+	read_all = kzalloc(sizeof(struct mcp_read_all), GFP_KERNEL);
+	if (!read_all)
+		return -ENOMEM;
+
+	read_all->cmd = READ_ALL;
+	len = hid_hw_output_report(mcp->hdev, (u8 *) read_all,
+			sizeof(struct mcp_read_all));
+
+	if (len != sizeof(struct mcp_read_all))
+		return -EINVAL;
+
+	kfree(read_all);
+	mutex_unlock(&mcp->lock);
+	t = wait_for_completion_timeout(&mcp->wait_in_report, msecs_to_jiffies(4000));
+	if (!t)
+		return -ETIMEDOUT;
+
+	/* return status, negative value if wrong response was received */
+	return mcp->status;
+}
+
+static void mcp_set_multiple(struct gpio_chip *gc, unsigned long *mask,
+				  unsigned long *bits)
+{
+	struct mcp2200 *mcp = gpiochip_get_data(gc);
+	u8 value;
+	int status;
+	struct mcp_set_clear_outputs *cmd;
+
+	cmd = kzalloc(sizeof(struct mcp_set_clear_outputs), GFP_KERNEL);
+	if (!cmd)
+		return;
+
+	mutex_lock(&mcp->lock);
+
+	value = mcp->gpio_val & ~*mask;
+	value |= (*mask & *bits);
+
+	cmd->cmd = SET_CLEAR_OUTPUTS;
+	cmd->set_bmap = value;
+	cmd->clear_bmap = ~(value);
+
+	status = hid_hw_output_report(mcp->hdev, (u8 *) cmd,
+		       sizeof(struct mcp_set_clear_outputs));
+	if (status == sizeof(struct mcp_set_clear_outputs))
+		mcp->gpio_val = value;
+
+	kfree(cmd);
+	mutex_unlock(&mcp->lock);
+}
+
+static void mcp_set(struct gpio_chip *gc, unsigned int gpio_nr, int value)
+{
+	unsigned long mask = (1 << gpio_nr);
+	unsigned long bmap_value = (value<<gpio_nr);
+
+	mcp_set_multiple(gc, &mask, &bmap_value);
+}
+
+static int mcp_get_multiple(struct gpio_chip *gc, unsigned long *mask,
+		unsigned long *bits)
+{
+	u32 val;
+	struct mcp2200 *mcp = gpiochip_get_data(gc);
+	int status;
+
+	status = mcp_cmd_read_all(mcp);
+	if (status != 0)
+		return status;
+
+	val = mcp->gpio_inval;
+	*bits = (val & *mask);
+	return 0;
+}
+
+static int mcp_get(struct gpio_chip *gc, unsigned int gpio_nr)
+{
+	unsigned long mask = 0, bits = 0;
+
+	mask = (1 << gpio_nr);
+	mcp_get_multiple(gc, &mask, &bits);
+	return (bits > 0) ? 1 : 0;
+}
+
+static int mcp_get_direction(struct gpio_chip *gc, unsigned int gpio_nr)
+{
+	struct mcp2200 *mcp = gpiochip_get_data(gc);
+
+	return (mcp->gpio_dir & (MCP2200_DIR_IN << gpio_nr))
+		? GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
+}
+
+static int mcp_set_direction(struct gpio_chip *gc, unsigned int gpio_nr,
+		enum MCP_IO_DIR io_direction)
+{
+	struct mcp2200 *mcp = gpiochip_get_data(gc);
+	struct mcp_configure *conf;
+	int status;
+	/* after the configure cmd we will need to set the outputs again */
+	unsigned long mask = ~(mcp->gpio_dir); /* only set outputs */
+	unsigned long bits = mcp->gpio_val;
+	/* Offsets of alternative pins in config_alt_pins, 0 is not used */
+	u8 alt_pin_conf[8] = {SSPND, USBCFG, 0, 0, 0, 0, RXLED, TXLED};
+	u8 config_alt_pins = mcp->config_alt_pins;
+
+	/* Read in the reset baudrate first, we need it later */
+	status = mcp_cmd_read_all(mcp);
+	if (status != 0)
+		return status;
+
+	conf = kzalloc(sizeof(struct mcp_configure), GFP_KERNEL);
+	if (!conf)
+		return -ENOMEM;
+	mutex_lock(&mcp->lock);
+
+	/* configure will reset the chip! */
+	conf->cmd = CONFIGURE;
+	conf->io_bmap = (mcp->gpio_dir & ~(1 << gpio_nr))
+		| (io_direction << gpio_nr);
+	/* Don't overwrite the reset parameters */
+	conf->baud_h = mcp->baud_h;
+	conf->baud_l = mcp->baud_l;
+	conf->config_alt_options = mcp->config_alt_options;
+	conf->io_default_val_bmap = mcp->gpio_reset_val;
+	/* Adjust alt. func if necessary */
+	if (alt_pin_conf[gpio_nr])
+		config_alt_pins &= ~(1 << alt_pin_conf[gpio_nr]);
+	conf->config_alt_pins = config_alt_pins;
+
+	status = hid_hw_output_report(mcp->hdev, (u8 *) conf,
+			sizeof(struct mcp_set_clear_outputs));
+	if (status == sizeof(struct mcp_set_clear_outputs)) {
+		mcp->gpio_dir &= ~(1 << gpio_nr);
+		mcp->config_alt_pins = config_alt_pins;
+	} else {
+		return -EIO;
+	}
+
+	kfree(conf);
+	mutex_unlock(&mcp->lock);
+
+	/* Configure CMD will clear all IOs -> rewrite them */
+	mcp_set_multiple(gc, &mask, &bits);
+	return 0;
+}
+
+static int mcp_direction_input(struct gpio_chip *gc, unsigned int gpio_nr)
+{
+	return mcp_set_direction(gc, gpio_nr, MCP2200_DIR_IN);
+}
+
+static int mcp_direction_output(struct gpio_chip *gc, unsigned int gpio_nr,
+		int value)
+{
+	int ret;
+	unsigned long mask, bmap_value;
+
+	mask = (1 << gpio_nr);
+	bmap_value = (value << gpio_nr);
+
+	ret = mcp_set_direction(gc, gpio_nr, MCP2200_DIR_OUT);
+	if (ret == 0)
+		mcp_set_multiple(gc, &mask, &bmap_value);
+	return ret;
+}
+
+
+static const struct gpio_chip template_chip = {
+	.label			= "mcp2200",
+	.owner			= THIS_MODULE,
+	.get_direction		= mcp_get_direction,
+	.direction_input	= mcp_direction_input,
+	.direction_output	= mcp_direction_output,
+	.set			= mcp_set,
+	.set_multiple		= mcp_set_multiple,
+	.get			= mcp_get,
+	.get_multiple		= mcp_get_multiple,
+	.base			= -1,
+	.ngpio			= MCP_NGPIO,
+	.can_sleep		= true,
+};
+
+/*
+ * MCP2200 uses interrupt endpoint for input reports. This function
+ * is called by HID layer when it receives i/p report from mcp2200,
+ * which is actually a response to the previously sent command.
+ */
+static int mcp2200_raw_event(struct hid_device *hdev, struct hid_report *report,
+		u8 *data, int size)
+{
+	struct mcp2200 *mcp = hid_get_drvdata(hdev);
+	struct mcp_read_all_resp *all_resp;
+
+	switch (data[0]) {
+	case READ_ALL:
+		all_resp = (struct mcp_read_all_resp *) data;
+		mcp->status = 0;
+		mcp->gpio_inval = all_resp->io_port_val_bmap;
+		mcp->baud_h = all_resp->baud_h;
+		mcp->baud_l = all_resp->baud_l;
+		mcp->gpio_reset_val = all_resp->io_default_val_bmap;
+		mcp->config_alt_pins = all_resp->config_alt_pins;
+		mcp->config_alt_options = all_resp->config_alt_options;
+		break;
+	default:
+		mcp->status = -EIO;
+		break;
+	}
+
+	complete(&mcp->wait_in_report);
+	return 1;
+}
+
+static void mcp2200_hid_unregister(void *ptr)
+{
+	struct hid_device *hdev = ptr;
+
+	hid_hw_close(hdev);
+	hid_hw_stop(hdev);
+}
+
+static int mcp2200_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+	struct mcp2200 *mcp;
+
+	mcp = devm_kzalloc(&hdev->dev, sizeof(*mcp), GFP_KERNEL);
+	if (!mcp)
+		return -ENOMEM;
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "can't parse reports\n");
+		return ret;
+	}
+
+	/*
+	 * This driver uses the .raw_event callback and therefore does not need any
+	 * HID_CONNECT_xxx flags.
+	 */
+	ret = hid_hw_start(hdev, 0);
+	if (ret) {
+		hid_err(hdev, "can't start hardware\n");
+		return ret;
+	}
+
+	hid_info(hdev, "USB HID v%x.%02x Device [%s] on %s\n", hdev->version >> 8,
+			hdev->version & 0xff, hdev->name, hdev->phys);
+
+	ret = hid_hw_open(hdev);
+	if (ret) {
+		hid_err(hdev, "can't open device\n");
+		hid_hw_stop(hdev);
+		return ret;
+	}
+
+	mutex_init(&mcp->lock);
+	init_completion(&mcp->wait_in_report);
+	hid_set_drvdata(hdev, mcp);
+	mcp->hdev = hdev;
+
+	ret = devm_add_action_or_reset(&hdev->dev, mcp2200_hid_unregister, hdev);
+	if (ret)
+		return ret;
+
+	mcp->gc = template_chip;
+	mcp->gc.parent = &hdev->dev;
+
+	ret = gpiochip_add_data(&mcp->gc, mcp);
+	if (ret < 0) {
+		dev_err(&hdev->dev, "Unable to register gpiochip\n");
+		hid_hw_stop(hdev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void mcp2200_remove(struct hid_device *hdev)
+{
+	struct mcp2200 *mcp;
+
+	mcp = hid_get_drvdata(hdev);
+	gpiochip_remove(&mcp->gc);
+}
+
+static const struct hid_device_id mcp2200_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MICROCHIP, USB_DEVICE_ID_MCP2200) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, mcp2200_devices);
+
+static struct hid_driver mcp2200_driver = {
+	.name		= "mcp2200",
+	.id_table	= mcp2200_devices,
+	.probe		= mcp2200_probe,
+	.remove		= mcp2200_remove,
+	.raw_event  = mcp2200_raw_event,
+};
+
+/* Register with HID core */
+module_hid_driver(mcp2200_driver);
+
+MODULE_AUTHOR("Johannes Roith <johannes@gnu-linux.rocks>");
+MODULE_DESCRIPTION("MCP2200 Microchip HID USB to GPIO bridge");
+MODULE_LICENSE("GPL");
-- 
2.41.0