Date:   Wed, 17 Jan 2018 14:58:40 +0100
From:   Marcus Folkesson <marcus.folkesson@...il.com>
To:     Dmitry Torokhov <dmitry.torokhov@...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: [PATCH v3] input: pxrc: new driver for PhoenixRC Flight
 Controller Adapter

Hello Dmitry,

On Tue, Jan 16, 2018 at 03:16:25PM -0800, Dmitry Torokhov wrote:
> Hi Marcus,
> 
> On Sat, Jan 13, 2018 at 09:15:32PM +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>
> > ---
> > v3:
> > 	- Use RUDDER and MISC instead of TILT_X and TILT_Y
> > 	- Drop kref and anchor
> > 	- Rework URB handling
> > 	- Add PM support
> 
> How did you test the PM support? By default the autopm is disabled on
> USB devices; you need to enable it by writing to sysfs (I believe you
> need to 'echo "auto" > /sys/bus/usb/<device>/power/control) and see if
> it gets autosuspended when not in use and resumed after you start
> interacting with it.

The test I've done is simply reading from the input device and then call
`pm-suspend`.
It works, suspend is called and reset_resume() will submit the URB
again. Without the PM code, the application did not read any events upon
resume.

However, I found another tricky part.
If I enable autosuspend (as you suggest) it will suspend when noone is
using the device. Good.

But when someone is opening the device, input_dev->users is counted up
to 1 before resume() is called. 
Is this intended?

This code (from resume()) will therefor allways submit the URB:

if (input_dev->users && usb_submit_urb(pxrc->urb, GFP_NOIO) < 0)


Then open() is called and fails because the urb is allready submitted.

input_dev->users is only incremented in input.c:input_open_device() what
I can tell?

I will move the submitting code to reset_resume() instead.


> 
> > 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        | 320 +++++++++++++++++++++++++++++++++++
> >  4 files changed, 387 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..ca11f646bae8
> > --- /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_RUDDER    |
> > ++---------+----------------+
> > +|     6   |  ABS_THROTTLE  |
> > ++---------+----------------+
> > +|     7   |  ABS_MISC      |
> > ++---------+----------------+
> > +
> > +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..98d9b8184c46
> > --- /dev/null
> > +++ b/drivers/input/joystick/pxrc.c
> > @@ -0,0 +1,320 @@
> > +// 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/uaccess.h>
> > +#include <linux/usb.h>
> > +#include <linux/usb/input.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 pxrc {
> > +	struct input_dev	*input;
> > +	struct usb_device	*udev;
> > +	struct usb_interface	*intf;
> > +	struct urb		*urb;
> > +	__u8			epaddr;
> > +	char			phys[64];
> > +	unsigned char           *data;
> > +	size_t			bsize;
> > +};
> > +
> > +static void pxrc_usb_irq(struct urb *urb)
> > +{
> > +	struct pxrc *pxrc = urb->context;
> > +	int error;
> > +
> > +	switch (urb->status) {
> > +	case 0:
> > +		/* success */
> > +		break;
> > +	case -ETIME:
> > +		/* this urb is timing out */
> > +		dev_dbg(&pxrc->intf->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->intf->dev, "%s - urb shutting down with status: %d\n",
> > +			__func__, urb->status);
> > +		return;
> > +	default:
> > +		dev_dbg(&pxrc->intf->dev, "%s - nonzero urb status received: %d\n",
> > +			__func__, urb->status);
> > +		goto exit;
> > +	}
> > +
> > +	if (urb->actual_length == 8) {
> > +		input_report_abs(pxrc->input, ABS_X, pxrc->data[0]);
> > +		input_report_abs(pxrc->input, ABS_Y, pxrc->data[2]);
> > +		input_report_abs(pxrc->input, ABS_RX, pxrc->data[3]);
> > +		input_report_abs(pxrc->input, ABS_RY, pxrc->data[4]);
> > +		input_report_abs(pxrc->input, ABS_RUDDER, pxrc->data[5]);
> > +		input_report_abs(pxrc->input, ABS_THROTTLE, pxrc->data[6]);
> > +		input_report_abs(pxrc->input, ABS_MISC, pxrc->data[7]);
> > +
> > +		input_report_key(pxrc->input, BTN_A, pxrc->data[1]);
> > +	}
> > +
> > +exit:
> 
> I think you need
> 
> 	usb_mark_last_busy(interface_to_usbdev(pxrc->intf));
> 
> here.
> 

Yes. Thank you.

> > +	/* Resubmit to fetch new fresh URBs */
> > +	error = usb_submit_urb(urb, GFP_ATOMIC);
> > +	if (error && error != -EPERM)
> > +		dev_err(&pxrc->intf->dev,
> > +			"%s - usb_submit_urb failed with result: %d",
> > +			__func__, error);
> > +}
> > +
> > +static int pxrc_open(struct input_dev *input)
> > +{
> > +	struct pxrc *pxrc = input_get_drvdata(input);
> > +	int retval;
> > +
> > +	retval = usb_autopm_get_interface(pxrc->intf);
> > +	if (retval) {
> > +		dev_err(&pxrc->intf->dev,
> > +			"%s - usb_autopm_get_interface failed, error: %d\n",
> > +			__func__, retval);
> > +		return retval;
> > +	}
> > +
> > +	retval = usb_submit_urb(pxrc->urb, GFP_KERNEL);
> > +	if (retval) {
> > +		dev_err(&pxrc->intf->dev,
> > +			"%s - usb_submit_urb failed, error: %d\n",
> > +			__func__, retval);
> > +		retval = -EIO;
> > +		goto out;
> > +	}
> > +
> > +	pxrc->intf->needs_remote_wakeup = 1;
> > +
> > +out:
> > +	usb_autopm_put_interface(pxrc->intf);
> > +	return retval;
> > +}
> > +
> > +static void pxrc_close(struct input_dev *input)
> > +{
> > +	struct pxrc *pxrc = input_get_drvdata(input);
> > +	int autopm_error;
> > +
> > +	autopm_error = usb_autopm_get_interface(pxrc->intf);
> > +
> > +	usb_kill_urb(pxrc->urb);
> > +	pxrc->intf->needs_remote_wakeup = 0;
> > +
> > +	if (!autopm_error)
> > +		usb_autopm_put_interface(pxrc->intf);
> > +}
> > +
> > +static int pxrc_usb_init(struct pxrc *pxrc)
> > +{
> > +	struct usb_endpoint_descriptor *epirq;
> > +	unsigned int pipe;
> > +	int retval;
> > +
> > +	/* Set up the endpoint information */
> > +	/* This device only has an interrupt endpoint */
> > +	retval = usb_find_common_endpoints(pxrc->intf->cur_altsetting,
> > +			NULL, NULL, &epirq, NULL);
> > +	if (retval) {
> > +		dev_err(&pxrc->intf->dev,
> > +			"Could not find endpoint\n");
> > +		goto error;
> > +	}
> > +
> > +	pxrc->bsize = usb_endpoint_maxp(epirq);
> > +	pxrc->epaddr = epirq->bEndpointAddress;
> > +	pxrc->data = devm_kmalloc(&pxrc->intf->dev, pxrc->bsize, GFP_KERNEL);
> > +	if (!pxrc->data) {
> > +		retval = -ENOMEM;
> > +		goto error;
> > +	}
> > +
> > +	usb_set_intfdata(pxrc->intf, pxrc);
> > +	usb_make_path(pxrc->udev, pxrc->phys, sizeof(pxrc->phys));
> > +	strlcat(pxrc->phys, "/input0", sizeof(pxrc->phys));
> > +
> > +	pxrc->urb = usb_alloc_urb(0, GFP_KERNEL);
> > +	if (!pxrc->urb) {
> > +		retval = -ENOMEM;
> > +		goto error;
> > +	}
> > +
> > +	pipe = usb_rcvintpipe(pxrc->udev, pxrc->epaddr),
> > +	usb_fill_int_urb(pxrc->urb, pxrc->udev, pipe, pxrc->data, pxrc->bsize,
> > +						pxrc_usb_irq, pxrc, 1);
> > +
> > +error:
> > +	return retval;
> > +
> > +
> > +}
> > +
> > +
> > +static int pxrc_input_init(struct pxrc *pxrc)
> > +{
> > +	pxrc->input = devm_input_allocate_device(&pxrc->intf->dev);
> > +	if (pxrc->input == NULL) {
> > +		dev_err(&pxrc->intf->dev, "couldn't allocate input device\n");
> > +		return -ENOMEM;
> > +	}
> > +
> > +	pxrc->input->name = "PXRC Flight Controller Adapter";
> > +	pxrc->input->phys = pxrc->phys;
> > +	usb_to_input_id(pxrc->udev, &pxrc->input->id);
> > +
> > +	pxrc->input->open = pxrc_open;
> > +	pxrc->input->close = pxrc_close;
> > +
> > +	input_set_capability(pxrc->input, EV_KEY, BTN_A);
> > +	input_set_abs_params(pxrc->input, ABS_X, 0, 255, 0, 0);
> > +	input_set_abs_params(pxrc->input, ABS_Y, 0, 255, 0, 0);
> > +	input_set_abs_params(pxrc->input, ABS_RX, 0, 255, 0, 0);
> > +	input_set_abs_params(pxrc->input, ABS_RY, 0, 255, 0, 0);
> > +	input_set_abs_params(pxrc->input, ABS_RUDDER, 0, 255, 0, 0);
> > +	input_set_abs_params(pxrc->input, ABS_THROTTLE, 0, 255, 0, 0);
> > +	input_set_abs_params(pxrc->input, ABS_MISC, 0, 255, 0, 0);
> > +
> > +	input_set_drvdata(pxrc->input, pxrc);
> > +
> > +	return input_register_device(pxrc->input);
> > +}
> > +
> > +static int pxrc_probe(struct usb_interface *intf,
> > +		      const struct usb_device_id *id)
> > +{
> > +	struct pxrc *pxrc;
> > +	int retval;
> > +
> > +	pxrc = devm_kzalloc(&intf->dev, sizeof(*pxrc), GFP_KERNEL);
> > +
> > +	if (!pxrc)
> > +		return -ENOMEM;
> > +
> > +	pxrc->udev = usb_get_dev(interface_to_usbdev(intf));
> > +	pxrc->intf = intf;
> > +
> > +	retval = pxrc_usb_init(pxrc);
> > +	if (retval)
> > +		goto error;
> > +
> > +	retval = pxrc_input_init(pxrc);
> > +	if (retval)
> > +		goto err_free_urb;
> > +
> > +	return 0;
> > +
> > +err_free_urb:
> > +	usb_free_urb(pxrc->urb);
> > +
> > +error:
> > +	return retval;
> > +}
> > +
> > +static void pxrc_disconnect(struct usb_interface *intf)
> > +{
> > +	struct pxrc *pxrc = usb_get_intfdata(intf);
> > +
> > +	usb_free_urb(pxrc->urb);
> > +	usb_set_intfdata(intf, NULL);
> > +}
> > +
> > +static int pxrc_suspend(struct usb_interface *intf, pm_message_t message)
> > +{
> > +	struct pxrc *pxrc = usb_get_intfdata(intf);
> > +	struct input_dev *input_dev = pxrc->input;
> > +
> > +	mutex_lock(&input_dev->mutex);
> > +	usb_kill_urb(pxrc->urb);
> > +	mutex_unlock(&input_dev->mutex);
> > +
> > +	return 0;
> > +}
> > +
> > +static int pxrc_resume(struct usb_interface *intf)
> > +{
> > +	struct pxrc *pxrc = usb_get_intfdata(intf);
> > +	struct input_dev *input_dev = pxrc->input;
> > +	int retval = 0;
> > +
> > +	mutex_lock(&input_dev->mutex);
> > +
> > +	if (input_dev->users && usb_submit_urb(pxrc->urb, GFP_NOIO) < 0)
> > +		retval = -EIO;
> > +
> > +	mutex_unlock(&input_dev->mutex);
> > +
> > +	return retval;
> > +}
> > +
> > +static int pxrc_pre_reset(struct usb_interface *intf)
> > +{
> > +	struct pxrc *pxrc = usb_get_intfdata(intf);
> > +	struct input_dev *input_dev = pxrc->input;
> > +
> > +	mutex_lock(&input_dev->mutex);
> > +	usb_kill_urb(pxrc->urb);
> > +
> > +	return 0;
> > +}
> > +
> > +static int pxrc_post_reset(struct usb_interface *intf)
> > +{
> > +	struct pxrc *pxrc = usb_get_intfdata(intf);
> > +	struct input_dev *input_dev = pxrc->input;
> > +	int retval = 0;
> > +
> > +	if (input_dev->users && usb_submit_urb(pxrc->urb, GFP_NOIO) < 0)
> > +		retval = -EIO;
> > +
> > +	mutex_unlock(&input_dev->mutex);
> > +
> > +	return retval;
> > +}
> > +
> > +static int pxrc_reset_resume(struct usb_interface *intf)
> > +{
> > +	return pxrc_resume(intf);
> > +}
> > +
> > +static struct usb_driver pxrc_driver = {
> > +	.name =		"pxrc",
> > +	.probe =	pxrc_probe,
> > +	.disconnect =	pxrc_disconnect,
> > +	.id_table =	pxrc_table,
> > +	.suspend	= pxrc_suspend,
> > +	.resume		= pxrc_resume,
> > +	.pre_reset	= pxrc_pre_reset,
> > +	.post_reset	= pxrc_post_reset,
> > +	.reset_resume	= pxrc_reset_resume,
> > +	.supports_autosuspend = 1,
> > +};
> > +
> > +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
> > 
> 
> Thank you.
> 
> -- 
> Dmitry


Best regards
Marcus Folkesson

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