help needed in this part of code regarding FF in hid-sony.c

4th attempt......

Hello to Mr. Roderick or to whom it may concren,

I am fei, a novice self-studied programming enthusiast, I need help
with hid-sony.c, but there is no relevant maintainer found in the
MAINTAINERS list, the closest is you, Mr. Roderick as the maintainer
of hid-playstation.c, so I just try my luck here, hope you don't mind.

The scenario as follow:

I have added a feature to make initial rumble vibrates when devices
are connected, code as follow (sony_play_effect() as reference) :

add delay.h

-----------------------------
#include <linux/delay.h>
-----------------------------





define a global variable "init_rumble"

------------------------------
......#define SONY_FF_SUPPORT (SIXAXIS_CONTROLLER | DUALSHOCK4_CONTROLLER)

bool init_rumble;
#define SONY_BT_DEVICE......
------------------------------




declare "init_rumble = true;" in sony_probe()


actual part

109 more lines

Hi Fei,

I'm not sure why you are trying to make such change kernel side, but
of course nothing is stopping you for personal use.

Kernel development is not easy and it is very easy to crash your
system. I can't say what is wrong here, but among the most common
issues are null pointer dereferences. If lucky the error is caught in
your kernel log, which should give you some clues on where the error
is coming from.

Also in your changes, I see you added some sleeps. Sleeping in the
kernel is taboo in a lot of places and depending on where is done can
also be a thing leading to issues as well. Depending on where you
tried to initiate some of this new code, the driver might not have
completed fully initializing, so some variables might not be set or
buffers might not be fully initialized.

Thanks,
Roderick

On Mon, Aug 30, 2021 at 12:11 AM fei fei [off-list ref] wrote:

4th attempt......

Hello to Mr. Roderick or to whom it may concren,

I am fei, a novice self-studied programming enthusiast, I need help
with hid-sony.c, but there is no relevant maintainer found in the
MAINTAINERS list, the closest is you, Mr. Roderick as the maintainer
of hid-playstation.c, so I just try my luck here, hope you don't mind.

The scenario as follow:

I have added a feature to make initial rumble vibrates when devices
are connected, code as follow (sony_play_effect() as reference) :

add delay.h

-----------------------------
#include <linux/delay.h>
-----------------------------





define a global variable "init_rumble"

------------------------------
......#define SONY_FF_SUPPORT (SIXAXIS_CONTROLLER | DUALSHOCK4_CONTROLLER)

bool init_rumble;
#define SONY_BT_DEVICE......
------------------------------




declare "init_rumble = true;" in sony_probe()

110 more quoted lines

Thanks Mr. Roderick for such quick reply, and sorry for redundant
emails, still not familiar with how linux kenel mailing list worked.

The purpose for doing this is to have an alternative way of
initialization/connection success indicator other than just the LEDs
in case of the leds broken/burnt, it's always better to have
alternative than no, isn't it?

I'll try digging in the kernel log see if I'm lucky enough to find
something useful.

For the sleep part, it's because I need to make adjustment to the
magnitude play duration for the initial rumble, if I take out the
sleep, the vibration will be long/simply no effect at all either
has/not has the sc->left/right = 0 part right after, thus unsuitable
for the initial rumble purpose(kinda weird). Never knew that it's
taboo to use sleep in kernel, as some articles out there suggested
that sleep is common in device driver.

It's actually trouble free if I just set the initial rumble as
independent function, but if I insist to merge it into
sony_play_effect( ), how would you suggest proper way to make it
right? Thanks.

Regards,
fei

On Tue, 31 Aug 2021 at 07:12, Roderick Colenbrander
[off-list ref] wrote:

Hi Fei,

I'm not sure why you are trying to make such change kernel side, but
of course nothing is stopping you for personal use.

Kernel development is not easy and it is very easy to crash your
system. I can't say what is wrong here, but among the most common
issues are null pointer dereferences. If lucky the error is caught in
your kernel log, which should give you some clues on where the error
is coming from.

Also in your changes, I see you added some sleeps. Sleeping in the
kernel is taboo in a lot of places and depending on where is done can
also be a thing leading to issues as well. Depending on where you
tried to initiate some of this new code, the driver might not have
completed fully initializing, so some variables might not be set or
buffers might not be fully initialized.

Thanks,
Roderick

On Mon, Aug 30, 2021 at 12:11 AM fei fei [off-list ref] wrote:

quoted

4th attempt......

Hello to Mr. Roderick or to whom it may concren,

I am fei, a novice self-studied programming enthusiast, I need help
with hid-sony.c, but there is no relevant maintainer found in the
MAINTAINERS list, the closest is you, Mr. Roderick as the maintainer
of hid-playstation.c, so I just try my luck here, hope you don't mind.

The scenario as follow:

I have added a feature to make initial rumble vibrates when devices
are connected, code as follow (sony_play_effect() as reference) :

add delay.h

133 more quoted lines

Hi Fei,

Thanks for your interest in adding this capability. I'm not sure if
this type of feature is desired in the Linux kernel directly. It is
not common practice to make a controller rumble at startup (not even
on game consoles). This driver is used in many devices (e.g. Android)
and such change would be a drastic behavior change.

If this is a behavior you would like to see for yourself, I would
recommend not to do this kernel side. You can easily add a udev rule
on your system to trigger a certain command upon discovery of a Sony
game controller as well as controllers from other vendors.

Thanks,
Roderick

On Mon, Aug 30, 2021 at 10:23 PM fei fei [off-list ref] wrote:

Thanks Mr. Roderick for such quick reply, and sorry for redundant
emails, still not familiar with how linux kenel mailing list worked.

The purpose for doing this is to have an alternative way of
initialization/connection success indicator other than just the LEDs
in case of the leds broken/burnt, it's always better to have
alternative than no, isn't it?

I'll try digging in the kernel log see if I'm lucky enough to find
something useful.

For the sleep part, it's because I need to make adjustment to the
magnitude play duration for the initial rumble, if I take out the
sleep, the vibration will be long/simply no effect at all either
has/not has the sc->left/right = 0 part right after, thus unsuitable
for the initial rumble purpose(kinda weird). Never knew that it's
taboo to use sleep in kernel, as some articles out there suggested
that sleep is common in device driver.

It's actually trouble free if I just set the initial rumble as
independent function, but if I insist to merge it into
sony_play_effect( ), how would you suggest proper way to make it
right? Thanks.

Regards,
fei

On Tue, 31 Aug 2021 at 07:12, Roderick Colenbrander
[off-list ref] wrote:

quoted

Hi Fei,

I'm not sure why you are trying to make such change kernel side, but
of course nothing is stopping you for personal use.

Kernel development is not easy and it is very easy to crash your
system. I can't say what is wrong here, but among the most common
issues are null pointer dereferences. If lucky the error is caught in
your kernel log, which should give you some clues on where the error

163 more quoted lines

Oh, I'm not familiar with linux kernel actually, if what I did is not
suitable for linux kernel space, I'll leave it just for my own use
then. And by the way, the environment I'm working on is Android device
actually, I wonder why something like this would be a drastic change.

udev rules is easy to access in linux but in Android I wonder how this
is to be done.

Anyway, get to know that you're on vacation in other mail, sorry for
occupied your precious personal time and thank you to help in my
inquiries, enjoy your vacation ^_^

On Thu, 2 Sept 2021 at 05:38, Roderick Colenbrander
[off-list ref] wrote:

Hi Fei,

Thanks for your interest in adding this capability. I'm not sure if
this type of feature is desired in the Linux kernel directly. It is
not common practice to make a controller rumble at startup (not even
on game consoles). This driver is used in many devices (e.g. Android)
and such change would be a drastic behavior change.

If this is a behavior you would like to see for yourself, I would
recommend not to do this kernel side. You can easily add a udev rule
on your system to trigger a certain command upon discovery of a Sony
game controller as well as controllers from other vendors.

Thanks,
Roderick

On Mon, Aug 30, 2021 at 10:23 PM fei fei [off-list ref] wrote:

quoted

Thanks Mr. Roderick for such quick reply, and sorry for redundant
emails, still not familiar with how linux kenel mailing list worked.

The purpose for doing this is to have an alternative way of
initialization/connection success indicator other than just the LEDs
in case of the leds broken/burnt, it's always better to have
alternative than no, isn't it?

I'll try digging in the kernel log see if I'm lucky enough to find
something useful.

For the sleep part, it's because I need to make adjustment to the
magnitude play duration for the initial rumble, if I take out the
sleep, the vibration will be long/simply no effect at all either
has/not has the sc->left/right = 0 part right after, thus unsuitable
for the initial rumble purpose(kinda weird). Never knew that it's
taboo to use sleep in kernel, as some articles out there suggested
that sleep is common in device driver.

It's actually trouble free if I just set the initial rumble as
independent function, but if I insist to merge it into

181 more quoted lines