Date:   Sun, 11 Jun 2023 21:02:11 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Johannes Roith <johannes@...-linux.rocks>, jikos@...nel.org
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] hid-mcp2200 added driver for MCP2200 GPIOs

Le 11/06/2023 à 18:48, Johannes Roith a écrit :
> 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@...-linux.rocks>

Hi,

a few nits below, should it help the review.

[...]

> --- /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@...-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>

Is this include needed?

> +#include <linux/completion.h>
> +#include <linux/delay.h>
> +#include <linux/hid.h>
> +#include <linux/hidraw.h>
> +#include <linux/gpio/driver.h>

Many maintainers prefer alphabetic order for includes.


> +#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
> +};

Does some
	#define xxx BIT(n)
would make more sense than this enum?

> +
> +/* 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,
> +

Uneeded new line.

> +};
> +
> +#define MCP_NGPIO 8
> +

[...]

> +/* 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;

Allocation could be deone before the lock.

> +
> +	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))

kfree(read_all); ?
(or move the call just below before the test)

> +		return -EINVAL;
> +
> +	kfree(read_all);
> +	mutex_unlock(&mcp->lock);

Mutex unlock could be done before kfree() or even before the "if 
(len..." a few lines above.

> +	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);

Mutex unlock could be done before kfree().

> +}
> +
> +static void mcp_set(struct gpio_chip *gc, unsigned int gpio_nr, int value)
> +{
> +	unsigned long mask = (1 << gpio_nr);

Uneeded ()
Does using BIT makes sense here?

> +	unsigned long bmap_value = (value<<gpio_nr);

Uneeded () and missing spaces aoud <<

> +
> +	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;

No need to init long (and maybe bits)

> +
> +	mask = (1 << gpio_nr);

Uneeded ()
Does using BIT makes sense here?

> +	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);

Mutex unlock could be done before kfree().

> +
> +	/* 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);

Uneeded ()
Does using BIT makes sense here?

> +	bmap_value = (value << gpio_nr);

Uneeded ()

> +
> +	ret = mcp_set_direction(gc, gpio_nr, MCP2200_DIR_OUT);
> +	if (ret == 0)
> +		mcp_set_multiple(gc, &mask, &bmap_value);
> +	return ret;
> +}
> +
> +

No need for 2 new lines.

[...]

> +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);

devm_gpiochip_add_data() and no .remove function?

> +	if (ret < 0) {
> +		dev_err(&hdev->dev, "Unable to register gpiochip\n");

hid_err() to be consistent?

> +		hid_hw_stop(hdev);

hid_hw_stop() would be called twice. Once here and once because of the 
devm_add_action_or_reset() above.


Just my 2c,

CJ

> +		return ret;
> +	}
> +
> +	return 0;
> +}

[...]

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