On 3/1/2014 08:53, Antonio Ospite wrote:
Hi Frank,
On Fri, 28 Feb 2014 22:58:55 -0500
Frank Praznik <frank.praznik@xxxxxxxxx> wrote:
This set consists of one bugfix, two mostly cosmetic changes and three larger
patches for the LED subsystem.
Patch #4 adds hardware blink support to the controller LEDs. Values from 0 to
2.5 seconds are supported by the hardware. The Sixaxis can set all of the LEDs
individually, but the DualShock 4 only has one global setting for the entire
light bar so only the value from the most recently set LED is used.
Adding this is OK, as it adds access to something supported by the
hardware.
Patch #5 adds an LED trigger that reports the controller battery status via the
registered LEDs. The LEDs will flash if the controller is charging or if the
battery is low, and remain solid otherwise.
This kind of logic _may_ belong to userspace. More comments in the
actual patch.
Functionally this trigger is no different from the ones registered by
the power supply system when a battery is registered, aside from the
specific conditions under which the LED blinks. I can understand the
reservations about setting it as the default, but at the same time it's
a trigger which can be easily disabled on the controller LEDs or be used
to control other LED devices if the user desires it.
If this is something best kept out of kernel code though, that's fine.
Patch #6 initializes the LEDs to a default value of LED 1 on the Sixaxis and
blue on the DualShock 4 so there is some indication that the controller is
powered on and connected in the case of Bluetooth. The code can be used to set
the LEDs based on the device number, but I'm not sure how to actually retrieve
the controller number from the system. I saw the xpad patches posted a few
weeks ago where the minor number of the joydev device was used, but I'm under
the impression that doing that is not ideal. Any suggestions?
Setting the controller number is done by the bluez sixaxis plugin[1]
(in bluez 5.x) following the X in /dev/input/jsX, this covers the
case of a mixed-joypad scenario, IMHO it makes sense that the
controller number matches the joystick device number.
Imagine js0->Sixaxis1, js1->wiimote, js2->Sixaxis2, I think it make
sense to have the LEDs on Sixaxis2 say "controller 3", not 2.
This has been done in userspace with libudev for 2 reasons:
1. the hid drivers should not have knowledge of the joystick layer;
2. kernel drivers should be as simple as possible, and try to just
exposing hardware functionalities but with as less "business logic"
as possible in them.
The current implementation in the bluez plugin uses hidraw, but support
for the sysfs led class could be added in order to avoid conflicts with
the rumble; IIRC, currently, setting rumble values could override the
LED settings done via hidraw, because the LEDs state is not tracked in
the latter case.
Ciao,
Antonio
[1]
http://git.kernel.org/cgit/bluetooth/bluez.git/tree/plugins/sixaxis.c
This can be done in the driver. See
https://www.mail-archive.com/linux-input@xxxxxxxxxxxxxxx/msg08103.html
It seems that the main problem with that patch is that modern systems
shouldn't be relying on joydev for this functionality. I'd like to know
what David Herrmann and Greg Kroah-Hartman came up with regarding the
solution mentioned in the reply as it would be nice to be able to set
the LEDs to the proper default values in the driver without needing to
rely on an external daemon. Setting the defaults in the driver doesn't
interfere with setting custom values after the device is initialized, so
there are no issues if the user wants to use a custom LED daemon.
As far as the behavior of patch #6 (setting the LEDs to the same number
or color on every connected device just to indicate that the controller
is turned on), the xpad and wiimote drivers both initialize the LEDs to
some default value where at least one is on to indicate that the
controller is powered on and connected to the system. The xpad driver
increments an atomic counter for assigning values as controllers are
connected and the wiimote always sets LED #1 to on. Not ideal, but it
serves it's purpose.
Personally I don't like the idea of relying on a BlueZ plugin to set the
controller LED values as it seems to bring a lot of issues with it:
users may not have BlueZ installed or enabled, some distros still use an
old version, the plugin relies on joydev to get the device number which
is why the patch I linked was NAKed, the current plugin implementation
doesn't set them via sysfs so the setting will be lost if force-feedback
is used and the plugin could conflict with other user-installed daemons
that set the LEDs (unless udev guarantees a notification order?). In
the latter scenario, the user could disable the plugin, but then you
lose the Sixaxis pairing functionality that it provides. I also have to
question as to why BlueZ is considered an appropriate place to set
controller LEDs, particularly on controllers that aren't connected via
Bluetooth.
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