hid-mcp2200: added driver for GPIOs of MCP2200

From: Johannes Roith <[email protected]>

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.

Feedback from reviewers Christophe JAILLET <[email protected]> and Andi Shyti <[email protected]> was added.

Changelog:

- v1: added driver
- v2: added ProductID in hid-ids.h
- v3: added feedback from review and make patch compilable
- v4: added more feedback from second review, tested as module and builtin on x86 and arm64
- v5: adopted Kconfig to style guidelines, fixed mcp_set_direction

Signed-off-by Johannes Roith <[email protected]>

---
 drivers/hid/Kconfig       |  10 +
 drivers/hid/Makefile      |   1 +
 drivers/hid/hid-ids.h     |   1 +
 drivers/hid/hid-mcp2200.c | 419 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 431 insertions(+)
 create mode 100644 drivers/hid/hid-mcp2200.c

drivers/hid/Kconfig +0 -0

index e11c1c803676..efe01b473cc2 100644
@@ -1301,6 +1301,16 @@ config HID_MCP2221
 	To compile this driver as a module, choose M here: the module
 	will be called hid-mcp2221.ko.
 

drivers/hid/hid-ids.h +0 -0

 #define USB_VENDOR_ID_MICROSOFT		0x045e
 #define USB_DEVICE_ID_SIDEWINDER_GV	0x003b

drivers/hid/hid-mcp2200.c new file +99 -0

new file mode 100644
index 000000000000..ed4483fa5bdf
@@ -0,0 +1,419 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MCP2200 - Microchip USB to GPIO bridge
+ *
+ * Copyright (c) 2023, Johannes Roith <[email protected]>
+ *
+ * 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/completion.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/hid.h>
+#include <linux/hidraw.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include "hid-ids.h"
+
+/* Commands codes in a raw output report */
+#define SET_CLEAR_OUTPUTS	0x08
+#define CONFIGURE		0x10
+#define READ_EE			0x20
+#define WRITE_EE		0x40
+#define READ_ALL		0x80
+
+/* MCP GPIO direction encoding */
+enum MCP_IO_DIR {
+	MCP2200_DIR_OUT = 0x00,
+	MCP2200_DIR_IN  = 0x01,
+};
+
+/* Altternative pin assignments */
+#define TXLED		2
+#define RXLED		3
+#define USBCFG		6
+#define 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;
+};
+

drivers/hid/hid-mcp2200.c new file +60 -0

+
+	read_all->cmd = READ_ALL;
+
+	mutex_lock(&mcp->lock);
+	len = hid_hw_output_report(mcp->hdev, (u8 *) read_all,
+				   sizeof(struct mcp_read_all));
+
+	mutex_unlock(&mcp->lock);
+	kfree(read_all);
+
+	if (len != sizeof(struct mcp_read_all))
+		return -EINVAL;
+
+	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;
+
+	mutex_unlock(&mcp->lock);
+	kfree(cmd);
+}
+
+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);
+}

drivers/hid/hid-mcp2200.c new file +78 -0

+
+	mask = (1 << gpio_nr);
+	mcp_get_multiple(gc, &mask, &bits);
+	return bits > 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 = conf->io_bmap;
+		mcp->config_alt_pins = config_alt_pins;
+	} else {
+		mutex_unlock(&mcp->lock);
+		kfree(conf);
+		return -EIO;
+	}
+
+	mutex_unlock(&mcp->lock);
+	kfree(conf);
+
+	/* 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,

drivers/hid/hid-mcp2200.c new file +38 -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;

drivers/hid/hid-mcp2200.c new file +30 -0

+}
+
+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);

drivers/hid/hid-mcp2200.c new file +11 -0

+		return ret;
+
+	mcp->gc = template_chip;
+	mcp->gc.parent = &hdev->dev;
+
+	ret = devm_gpiochip_add_data(&hdev->dev, &mcp->gc, mcp);
+	if (ret < 0) {
+		hid_err(hdev, "Unable to register gpiochip\n");
+		return ret;
+	}
+

drivers/hid/hid-mcp2200.c new file +12 -0

+}
+
+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,

My personal recommendation is to just have a single DMA buffer allocated for the mcp2200 instance rather than having to call the allocator and release the memory per command.

The reason you run into this is likely because of the action added to devm conflicting with hid_device_remove....

I recommend not depending on devm for teardown rather than making a stub remove function to work around the issue.