Message-ID: <20180111003714.34kgsbdtaqjwuyis@dtor-ws>
Date:   Wed, 10 Jan 2018 16:37:14 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Tomohiro Yoshidomi <sylph23k@...il.com>,
        David Herrmann <dh.herrmann@...il.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-input@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v2] input: pxrc: new driver for PhoenixRC Flight
 Controller Adapter

Hi Marcus,

On Wed, Jan 10, 2018 at 02:11:39PM +0100, Marcus Folkesson wrote:
> This driver let you plug in your RC controller to the adapter and
> use it as input device in various RC simulators.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
> ---
> v2:
> 	- Change module license to GPLv2 to match SPDX tag
> 
>  Documentation/input/devices/pxrc.rst |  57 ++++++++
>  drivers/input/joystick/Kconfig       |   9 ++
>  drivers/input/joystick/Makefile      |   1 +
>  drivers/input/joystick/pxrc.c        | 254 +++++++++++++++++++++++++++++++++++
>  4 files changed, 321 insertions(+)
>  create mode 100644 Documentation/input/devices/pxrc.rst
>  create mode 100644 drivers/input/joystick/pxrc.c
> 
> diff --git a/Documentation/input/devices/pxrc.rst b/Documentation/input/devices/pxrc.rst
> new file mode 100644
> index 000000000000..0ec466c58958
> --- /dev/null
> +++ b/Documentation/input/devices/pxrc.rst
> @@ -0,0 +1,57 @@
> +=======================================================
> +pxrc - PhoenixRC Flight Controller Adapter
> +=======================================================
> +
> +:Author: Marcus Folkesson <marcus.folkesson@...il.com>
> +
> +This driver let you use your own RC controller plugged into the
> +adapter that comes with PhoenixRC [1]_ or other compatible adapters.
> +
> +The adapter supports 7 analog channels and 1 digital input switch.
> +
> +Notes
> +=====
> +
> +Many RC controllers is able to configure which stick goes to which channel.
> +This is also configurable in most simulators, so a matching is not necessary.
> +
> +The driver is generating the following input event for analog channels:
> +
> ++---------+----------------+
> +| Channel |      Event     |
> ++=========+================+
> +|     1   |  ABS_X         |
> ++---------+----------------+
> +|     2   |  ABS_Y         |
> ++---------+----------------+
> +|     3   |  ABS_RX        |
> ++---------+----------------+
> +|     4   |  ABS_RY        |
> ++---------+----------------+
> +|     5   |  ABS_TILT_X    |
> ++---------+----------------+
> +|     6   |  ABS_TILT_Y    |
> ++---------+----------------+

TILT are normally reserved for stylus/pen. Do we have better event codes
maybe? Is there a picture of the RC so I can make more sense of the
proposed event assignment?

> +|     7   |  ABS_THROTTLE  |
> ++---------+----------------+
> +
> +The digital input switch is generated as an `BTN_A` event.
> +
> +Manual Testing
> +==============
> +
> +To test this driver's functionality you may use `input-event` which is part of
> +the `input layer utilities` suite [2]_.
> +
> +For example::
> +
> +    > modprobe pxrc
> +    > input-events <devnr>
> +
> +To print all input events from input `devnr`.
> +
> +References
> +==========
> +
> +.. [1] http://www.phoenix-sim.com/
> +.. [2] https://www.kraxel.org/cgit/input/
> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
> index f3c2f6ea8b44..18ab6dafff41 100644
> --- a/drivers/input/joystick/Kconfig
> +++ b/drivers/input/joystick/Kconfig
> @@ -351,4 +351,13 @@ config JOYSTICK_PSXPAD_SPI_FF
>  
>  	  To drive rumble motor a dedicated power supply is required.
>  
> +config JOYSTICK_PXRC
> +	tristate "PhoenixRC Flight Controller Adapter"
> +	depends on USB_ARCH_HAS_HCD
> +	select USB
> +	help
> +	  Say Y here if you want to use the PhoenixRC Flight Controller Adapter.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called pxrc.
>  endif
> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
> index 67651efda2e1..dd0492ebbed7 100644
> --- a/drivers/input/joystick/Makefile
> +++ b/drivers/input/joystick/Makefile
> @@ -23,6 +23,7 @@ obj-$(CONFIG_JOYSTICK_JOYDUMP)		+= joydump.o
>  obj-$(CONFIG_JOYSTICK_MAGELLAN)		+= magellan.o
>  obj-$(CONFIG_JOYSTICK_MAPLE)		+= maplecontrol.o
>  obj-$(CONFIG_JOYSTICK_PSXPAD_SPI)	+= psxpad-spi.o
> +obj-$(CONFIG_JOYSTICK_PXRC)			+= pxrc.o
>  obj-$(CONFIG_JOYSTICK_SIDEWINDER)	+= sidewinder.o
>  obj-$(CONFIG_JOYSTICK_SPACEBALL)	+= spaceball.o
>  obj-$(CONFIG_JOYSTICK_SPACEORB)		+= spaceorb.o
> diff --git a/drivers/input/joystick/pxrc.c b/drivers/input/joystick/pxrc.c
> new file mode 100644
> index 000000000000..2bec99df97e2
> --- /dev/null
> +++ b/drivers/input/joystick/pxrc.c
> @@ -0,0 +1,254 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for Phoenix RC Flight Controller Adapter
> + *
> + * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@...il.com>
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/kref.h>
> +#include <linux/uaccess.h>
> +#include <linux/usb.h>
> +#include <linux/mutex.h>
> +#include <linux/input.h>
> +
> +#define PXRC_VENDOR_ID	(0x1781)
> +#define PXRC_PRODUCT_ID	(0x0898)
> +
> +static const struct usb_device_id pxrc_table[] = {
> +	{ USB_DEVICE(PXRC_VENDOR_ID, PXRC_PRODUCT_ID) },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(usb, pxrc_table);
> +
> +struct usb_pxrc {
> +	struct input_dev	*input_dev;
> +	struct usb_device	*udev;
> +	struct usb_interface	*interface;
> +	struct usb_anchor	anchor;
> +	__u8			epaddr;
> +	char			phys[64];
> +	unsigned char           *data;
> +	size_t			bsize;
> +	struct kref		kref;
> +};
> +
> +#define to_pxrc_dev(d) container_of(d, struct usb_pxrc, kref)
> +static void pxrc_delete(struct kref *kref)
> +{
> +	struct usb_pxrc *pxrc = to_pxrc_dev(kref);
> +
> +	usb_put_dev(pxrc->udev);
> +}
> +
> +static void pxrc_usb_irq(struct urb *urb)
> +{
> +	struct usb_pxrc *pxrc = urb->context;
> +
> +	switch (urb->status) {
> +	case 0:
> +		/* success */
> +		break;
> +	case -ETIME:
> +		/* this urb is timing out */
> +		dev_dbg(&pxrc->interface->dev,
> +			"%s - urb timed out - was the device unplugged?\n",
> +			__func__);
> +		return;
> +	case -ECONNRESET:
> +	case -ENOENT:
> +	case -ESHUTDOWN:
> +	case -EPIPE:
> +		/* this urb is terminated, clean up */
> +		dev_dbg(&pxrc->interface->dev, "%s - urb shutting down with status: %d\n",
> +			__func__, urb->status);
> +		return;
> +	default:
> +		dev_dbg(&pxrc->interface->dev, "%s - nonzero urb status received: %d\n",
> +			__func__, urb->status);
> +		goto exit;
> +	}
> +
> +	if (urb->actual_length == 8) {
> +		input_report_abs(pxrc->input_dev, ABS_X, pxrc->data[0]);
> +		input_report_abs(pxrc->input_dev, ABS_Y, pxrc->data[2]);
> +		input_report_abs(pxrc->input_dev, ABS_RX, pxrc->data[3]);
> +		input_report_abs(pxrc->input_dev, ABS_RY, pxrc->data[4]);
> +		input_report_abs(pxrc->input_dev, ABS_TILT_X, pxrc->data[5]);
> +		input_report_abs(pxrc->input_dev, ABS_TILT_Y, pxrc->data[6]);
> +		input_report_abs(pxrc->input_dev, ABS_THROTTLE, pxrc->data[7]);
> +
> +		input_report_key(pxrc->input_dev, BTN_A, pxrc->data[1]);
> +	}
> +
> +exit:
> +	/* Resubmit to fetch new fresh URBs */
> +	usb_anchor_urb(urb, &pxrc->anchor);
> +	if (usb_submit_urb(urb, GFP_ATOMIC) < 0)
> +		usb_unanchor_urb(urb);
> +}
> +
> +static int pxrc_submit_intr_urb(struct usb_pxrc *pxrc)
> +{
> +	struct urb *urb;
> +	unsigned int pipe;
> +	int err;
> +
> +	urb = usb_alloc_urb(0, GFP_KERNEL);
> +	if (!urb)
> +		return -ENOMEM;
> +
> +	pipe = usb_rcvintpipe(pxrc->udev, pxrc->epaddr),
> +	usb_fill_int_urb(urb, pxrc->udev, pipe, pxrc->data, pxrc->bsize,
> +						pxrc_usb_irq, pxrc, 1);
> +	usb_anchor_urb(urb, &pxrc->anchor);
> +	err = usb_submit_urb(urb, GFP_KERNEL);
> +	if (err < 0)
> +		usb_unanchor_urb(urb);
> +
> +	usb_free_urb(urb);
> +	return err;
> +}
> +
> +static int pxrc_open(struct input_dev *input)
> +{
> +	struct usb_pxrc *pxrc = input_get_drvdata(input);
> +	int err;
> +
> +	err = pxrc_submit_intr_urb(pxrc);
> +	if (err < 0)
> +		goto error;
> +
> +	kref_get(&pxrc->kref);
> +	return 0;
> +
> +error:
> +	usb_kill_anchored_urbs(&pxrc->anchor);
> +	return err;
> +}
> +
> +static void pxrc_close(struct input_dev *input)
> +{
> +	struct usb_pxrc *pxrc = input_get_drvdata(input);
> +
> +	usb_kill_anchored_urbs(&pxrc->anchor);
> +	kref_put(&pxrc->kref, pxrc_delete);

This is way to complex and I am not sure why you need to anchor URBs and
have a separate refcounting, etc. I do not think it is even safe with
module unloading as kref might be in flight as you run through module
unload and devm will destroy most of the objects.

Why don't you simply use usb_kill_urb() here and be done.
input_unregister_device() that is called as part of devm unwind on
device unbind will make sure that pxrc_close() is called.

Thanks.

> +}
> +
> +static int pxrc_input_init(struct usb_pxrc *pxrc)
> +{
> +	pxrc->input_dev = devm_input_allocate_device(&pxrc->interface->dev);
> +	if (pxrc->input_dev == NULL) {
> +		dev_err(&pxrc->interface->dev, "couldn't allocate input device\n");
> +		return -ENOMEM;
> +	}
> +
> +	pxrc->input_dev->name = "PXRC Flight Controller Adapter";
> +	pxrc->input_dev->phys = pxrc->phys;
> +	pxrc->input_dev->id.bustype = BUS_USB;
> +	pxrc->input_dev->id.vendor = PXRC_VENDOR_ID;
> +	pxrc->input_dev->id.product = PXRC_PRODUCT_ID;
> +	pxrc->input_dev->id.version = 0x01;

	usb_to_input_id(udev, &pxrc->input_dev->id);

> +
> +	pxrc->input_dev->open = pxrc_open;
> +	pxrc->input_dev->close = pxrc_close;
> +
> +	pxrc->input_dev->evbit[0] =	BIT_MASK(EV_ABS) | BIT_MASK(EV_KEY);
> +	pxrc->input_dev->absbit[0] =	BIT_MASK(ABS_X) |
> +					BIT_MASK(ABS_Y) |
> +					BIT_MASK(ABS_RY) |
> +					BIT_MASK(ABS_RX) |
> +					BIT_MASK(ABS_THROTTLE) |
> +					BIT_MASK(ABS_TILT_X) |
> +					BIT_MASK(ABS_TILT_Y);

Not needed, it will be done as part of input_set_abs_params() below.

> +
> +	pxrc->input_dev->keybit[BIT_WORD(BTN_JOYSTICK)] = BIT_MASK(BTN_A);

input_set_capability(pxrc->input_dev, EV_KEY, BTN_A);

> +
> +	input_set_abs_params(pxrc->input_dev, ABS_X, 0, 255, 0, 0);
> +	input_set_abs_params(pxrc->input_dev, ABS_Y, 0, 255, 0, 0);
> +	input_set_abs_params(pxrc->input_dev, ABS_RX, 0, 255, 0, 0);
> +	input_set_abs_params(pxrc->input_dev, ABS_RY, 0, 255, 0, 0);
> +	input_set_abs_params(pxrc->input_dev, ABS_TILT_X, 0, 255, 0, 0);
> +	input_set_abs_params(pxrc->input_dev, ABS_TILT_Y, 0, 255, 0, 0);
> +	input_set_abs_params(pxrc->input_dev, ABS_THROTTLE, 0, 255, 0, 0);
> +
> +	input_set_drvdata(pxrc->input_dev, pxrc);
> +
> +	return input_register_device(pxrc->input_dev);
> +}
> +
> +static int pxrc_probe(struct usb_interface *interface,
> +		      const struct usb_device_id *id)
> +{
> +	struct usb_pxrc *pxrc;
> +	struct usb_endpoint_descriptor *epirq;
> +	int retval;
> +
> +	pxrc = devm_kzalloc(&interface->dev, sizeof(*pxrc), GFP_KERNEL);
> +
> +	if (!pxrc)
> +		return -ENOMEM;
> +
> +	kref_init(&pxrc->kref);
> +	init_usb_anchor(&pxrc->anchor);
> +
> +	pxrc->udev = usb_get_dev(interface_to_usbdev(interface));
> +	pxrc->interface = interface;
> +
> +	/* Set up the endpoint information */
> +	/* This device only has an interrupt endpoint */
> +	retval = usb_find_common_endpoints(interface->cur_altsetting,
> +			NULL, NULL, &epirq, NULL);
> +	if (retval) {
> +		dev_err(&interface->dev,
> +			"Could not find endpoint\n");
> +		goto error;
> +	}
> +
> +	pxrc->bsize = usb_endpoint_maxp(epirq);
> +	pxrc->epaddr = epirq->bEndpointAddress;
> +	pxrc->data = devm_kmalloc(&interface->dev, pxrc->bsize, GFP_KERNEL);
> +	if (!pxrc->data) {
> +		retval = -ENOMEM;
> +		goto error;
> +	}
> +
> +	usb_set_intfdata(interface, pxrc);
> +	usb_make_path(pxrc->udev, pxrc->phys, sizeof(pxrc->phys));
> +
> +	retval = pxrc_input_init(pxrc);
> +	if (retval)
> +		goto error;
> +
> +	return 0;
> +
> +error:
> +	/* this frees allocated memory */
> +	kref_put(&pxrc->kref, pxrc_delete);
> +
> +	return retval;
> +}
> +
> +static void pxrc_disconnect(struct usb_interface *interface)
> +{
> +	struct usb_pxrc *pxrc = usb_get_intfdata(interface);
> +
> +	kref_put(&pxrc->kref, pxrc_delete);
> +}
> +
> +static struct usb_driver pxrc_driver = {
> +	.name =		"pxrc",
> +	.probe =	pxrc_probe,
> +	.disconnect =	pxrc_disconnect,
> +	.id_table =	pxrc_table,
> +};
> +
> +module_usb_driver(pxrc_driver);
> +
> +MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@...il.com>");
> +MODULE_DESCRIPTION("PhoenixRC Flight Controller Adapter");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.15.1
> 

Thanks.

-- 
Dmitry

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