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Date:   Wed, 21 Feb 2018 21:21:07 +0100
From:   Rodrigo Rivas Costa <rodrigorivascosta@gmail.com>
To:     "Pierre-Loup A. Griffais" <pgriffais@valvesoftware.com>
Cc:     Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        linux-kernel@vger.kernel.org, linux-input@vger.kernel.org
Subject: Re: [PATCH v2 0/3] new driver for Valve Steam Controller
Message-ID: <20180221202107.GA21140@casa>
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 <20180220232035.GA28798@casa>
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On Tue, Feb 20, 2018 at 04:09:39PM -0800, Pierre-Loup A. Griffais wrote:
> On 02/20/2018 03:20 PM, Rodrigo Rivas Costa wrote:
> > On Tue, Feb 20, 2018 at 02:29:48PM -0800, Pierre-Loup A. Griffais wrote:
> > About the left trackpad/joystick, currently I'm not treating them
> > different. I'm out of ABS axes, and anyway, it is not likely that the
> > left pad and the joystick be used at the same time (I only have one left
> > thumb). Nevertheless, if we really want to make them apart, we can use
> > bits 10.3 (lpad_touch) and 10.7 (lpad_and_joy) together. I described the
> > details in [2], but I'm not currently doing that in this driver.
> 
> I didn't necessarily mean exposing it, but in the event a user is using both
> at the same time (it happens, using claw grip with some games is necessary
> to use the D-pad while deflecting the stick), then you'll most likely run
> into issues unless you demux the inbound data, since we were also out of
> left analog fields and mux them together if used at the same time. Not sure
> if you're already handling that case, but not doing it would result in the
> stick appearing to fully deflect every other input report if the user is
> doing both at the same time.

"Claw grip"? Is that a real thing? Yes, it is! Well, you're totally
right. I think that it will be best to fully separate the left-pad and
the joystick. Maybe the left-pad can be mapped to ABS_HAT1{X,Y]...

> > About the gyroscope/acceleration/quaternion, you know the issue
> > that the wireless gives gyro plus quat but no accel, while the wired
> > gives all three. My general idea is to create an additional input device
> > with INPUT_PROP_ACCELEROMETER to expose what is available. Pity is that
> > the wireless gives no accel, maybe there is some command to enable it?
> 
> It should be three neighboring bits for that setting; does this not work for
> you?
> 
> // Bitmask that define which IMU features to enable.
> typedef enum
> {
> 	SETTING_GYRO_MODE_OFF				= 0x0000,
> 	SETTING_GYRO_MODE_STEERING			= 0x0001,
> 	SETTING_GYRO_MODE_TILT				= 0x0002,
> 	SETTING_GYRO_MODE_SEND_ORIENTATION	= 0x0004,
> 	SETTING_GYRO_MODE_SEND_RAW_ACCEL	= 0x0008,
> 	SETTING_GYRO_MODE_SEND_RAW_GYRO		= 0x0010,
> } SettingGyroMode;

Thanks for that, it will be useful! Those are the values to be written
to what I called "register 0x30" with {0x87 0x03 0x30 X 0x00}. Currently
I am writing 0x14 to enable and 0x00 to disable. I suspected it was a
bit-field...

> In general I'm concerned about sending of the gyro-enable message
> potentially impairing Steam functionality if it's running at the same time
> (eg. if gyro gets disabled over the radio while Steam still needs it), or
> sending any stateful messages to the device. For instance, are you ever
> sending the "blank configuration" setting? I assume you must be or users
> would still get keyboard/mouse input over these USB endpoints while trying
> to interact with the controller. But sending this after Steam programmed a
> setting, or instructed the controller to go back to lizard mode because it
> was requested by a configuration, would be problematic.

Sure, but this patchset should be safe, shouldn't it?
Maube future patches that play with the gyro/force-feedback could be
disabled by default, and could need a module parameter to be enabled.
That way Steam Client will work out-of-the-box anywhere but proficient
users could use the extra functionality easily.

Related to that, Benjamin Tissoires replied to 1/3:
> > --- a/drivers/hid/hid-quirks.c
> > +++ b/drivers/hid/hid-quirks.c
> > @@ -629,6 +629,10 @@ static const struct hid_device_id
> > hid_have_special_driver[] = {
> >  #if IS_ENABLED(CONFIG_HID_SPEEDLINK)
> >         { HID_USB_DEVICE(USB_VENDOR_ID_X_TENSIONS,
> >         USB_DEVICE_ID_SPEEDLINK_VAD_CEZANNE) },
> >  #endif
> > +#if IS_ENABLED(CONFIG_HID_STEAM)
> > +       { HID_USB_DEVICE(USB_VENDOR_ID_VALVE, USB_DEVICE_ID_STEAM_CONTROLLER) },
> > +       { HID_USB_DEVICE(USB_VENDOR_ID_VALVE, USB_DEVICE_ID_STEAM_CONTROLLER_WIRELESS) },
> > +#endif
> 
> In addition to the discussion in 0/3, I wonder if you should not
> remove this hunk. Unless having hid-generic binding the device before
> your hid-steam driver, it would be better not force the Steam boxes to
> use your driver.

I don't really see the point on that. If we do that I'll have to unbind
and bind the device manually, and that is a pain, and impossible without
root (my ultimate goal is to use this controller with my Tizen TV ;-P).

And anyway this driver is mostly harmless, the only visible changes from
userspace are the new input and power devices, and that the virtual
keyboard/mouse are no more. If the virtual devices are really missed we
could use:

	hid_hw_start(hdev, HID_CONNECT_DEFAULT);

on them, maybe with a module parameter? Note that one of the first
things the Steam Client does is to disable the virtual devices (with a
command to the device).
(TBH I always had the impression that those virtual devices are there
to move the Grub menu...)

If Valve people really feel that this driver is not needed for SteamOS,
because the Steam Client is always running, then SteamOS can always do
CONFIG_HID_STEAM=n.

Regards.
Rodrigo