User space <==> kernel space for device wakeups.
Hi, I want a user process to be notified on device wakeup so that I can print some related information. Which framework to use for this?(events, .. ??) One idea I get is to log the info into <debugfs> and poll(implement my poll) on it for data. This is my last option. Are there any better ways? Best Regards, Manty
On Wed, Oct 08, 2014 at 04:39:17PM +0900, manty kuma wrote:
Hi, I want a user process to be notified on device wakeup so that I can print some related information.
Really? My device can "wakeup" thousands of times a second, what are you going to do with that type of information?
Which framework to use for this?(events, .. ??)
One idea I get is to log the info into <debugfs> and poll(implement my poll) on it for data. This is my last option.
Are there any better ways?
What problem are you trying to solve here? thanks, greg k-h
Wayback when I was working on some project to wake up userspace program for every rising edge in GPIO pin (hall sensor), I use to send signal to the PID from kernel, before that userspace has to register its PID with kernel module. Max interrupts I have tested is some 100 times per second I.e. 100 times wakes up userspace application per second. It was working quite well.. But today also I don't know what other thing can be used for this case, as it is asynchronous. Sent from my Android phone with Gmail. Please excuse my brevity. On 08-Oct-2014 7:03 pm, "Greg KH" <greg@kroah.com> wrote:
On Wed, Oct 08, 2014 at 04:39:17PM +0900, manty kuma wrote:
Hi, I want a user process to be notified on device wakeup so that I can print some related information.
Really? My device can "wakeup" thousands of times a second, what are you going to do with that type of information?
Which framework to use for this?(events, .. ??)
One idea I get is to log the info into <debugfs> and poll(implement my poll) on it for data. This is my last option.
Are there any better ways?
What problem are you trying to solve here?
thanks,
greg k-h
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
On 2014-10-08 21:14:43 (+0530), Jeshwanth Kumar N K <jeshkumar555@gmail.com> wrote:
Wayback when I was working on some project to wake up userspace program for every rising edge in GPIO pin (hall sensor), I use to send signal to the PID from kernel, before that userspace has to register its PID with kernel module.
I've seen a certain vendor[1] do something similar. They saved the task pointer for whichever process made the magical ioctl() call and used it to send signals from the interrupt handler. It worked, right up to the point where the process went away and then the kernel panicked. Regards, Kristof [1] Who shall remain nameless here. Naming them would only give people the impression that other vendors might be better.
On Wed, Oct 08, 2014 at 05:57:50PM +0200, Kristof Provost wrote:
On 2014-10-08 21:14:43 (+0530), Jeshwanth Kumar N K <jeshkumar555@gmail.com> wrote:
Wayback when I was working on some project to wake up userspace program for every rising edge in GPIO pin (hall sensor), I use to send signal to the PID from kernel, before that userspace has to register its PID with kernel module.
I've seen a certain vendor[1] do something similar. They saved the task pointer for whichever process made the magical ioctl() call and used it to send signals from the interrupt handler. It worked, right up to the point where the process went away and then the kernel panicked.
Exactly, don't do that :) Finding out the real problem that is attempting to be solved would be good... greg k-h
Greg, then what will you suggest for my case? I mean any alternative ? Thanks On Wed, Oct 8, 2014 at 9:55 PM, Greg Kroah-Hartman <greg@kroah.com> wrote:
On Wed, Oct 08, 2014 at 05:57:50PM +0200, Kristof Provost wrote:
On 2014-10-08 21:14:43 (+0530), Jeshwanth Kumar N K < jeshkumar555@gmail.com> wrote:
Wayback when I was working on some project to wake up userspace program for every rising edge in GPIO pin (hall sensor), I use to send signal to the PID from kernel, before that userspace has to register its PID with kernel module.
I've seen a certain vendor[1] do something similar. They saved the task pointer for whichever process made the magical ioctl() call and used it to send signals from the interrupt handler. It worked, right up to the point where the process went away and then the kernel panicked.
Exactly, don't do that :)
Finding out the real problem that is attempting to be solved would be good...
greg k-h
-- Regards Jeshwanth Kumar N K Bangalore, India
A: No. Q: Should I include quotations after my reply? http://daringfireball.net/2007/07/on_top On Wed, Oct 08, 2014 at 10:01:43PM +0530, Jeshwanth Kumar N K wrote:
Greg, then what will you suggest for my case? I mean any alternative ?
What "case"? What problem are you trying to solve? greg k-h
On Wed, Oct 8, 2014 at 10:08 PM, Greg Kroah-Hartman <greg@kroah.com> wrote:
A: No. Q: Should I include quotations after my reply?
http://daringfireball.net/2007/07/on_top
On Wed, Oct 08, 2014 at 10:01:43PM +0530, Jeshwanth Kumar N K wrote:
Greg, then what will you suggest for my case? I mean any alternative ?
What "case"? What problem are you trying to solve?
greg k-h
Oh, correct. 2nd time I am warned on this (may be practise by using outlook). Will reply bottom now onwards - sorry. My case was: I have a hall sensor connected to Beaglebone black, And Userspace needed a wakeup once the interrupt occur (example: every rising edge of GPIO). Before that, the program will register (ioctl) the User space task pointer with my kernel module, then my kernel module start sending signal for every interrupt occur. We can consider roughly around 100 to 200 interrupts per second maximum. ( I have not done this, but may be we can consider kernel will get notified when userspace program stops. so that it will not send any signal). So for this case, any other alternative implementation ? Thanks -- Regards Jeshwanth Kumar N K Bangalore, India
On Wed, Oct 08, 2014 at 10:23:32PM +0530, Jeshwanth Kumar N K wrote:
My case was: I have a hall sensor connected to Beaglebone black, And Userspace needed a wakeup once the interrupt occur (example: every rising edge of GPIO). Before that, the program will register (ioctl) the User space task pointer with my kernel module, then my kernel module start sending signal for every interrupt occur. We can consider roughly around 100 to 200 interrupts per second maximum. ( I have not done this, but may be we can consider kernel will get notified when userspace program stops. so that it will not send any signal). So for this case, any other alternative implementation ?
select() on the GPIO sysfs file instead of a custom ioctl? And what do you do in userspace with that information? greg k-h
On Wed, Oct 8, 2014 at 11:02 PM, Greg Kroah-Hartman <greg@kroah.com> wrote:
On Wed, Oct 08, 2014 at 10:23:32PM +0530, Jeshwanth Kumar N K wrote:
My case was: I have a hall sensor connected to Beaglebone black, And Userspace needed a wakeup once the interrupt occur (example: every rising edge of GPIO). Before that, the program will register (ioctl) the User space task pointer with my kernel module, then my kernel module start sending signal for every interrupt occur. We can consider roughly around 100 to 200 interrupts per second maximum. ( I have not done this, but may be we can consider kernel will get notified when userspace program stops. so that it will not send any signal). So for this case, any other alternative implementation ?
select() on the GPIO sysfs file instead of a custom ioctl?
And what do you do in userspace with that information?
greg k-h
With hall sensor input I can get the position of motor, and in userspace I drive the motor (brushless) for next position by passing the values to sysfs attribute of PWM driver. It's a closed loop, until I drive the PWM I will not get an interrupt. But what solution I had was, anyway PWM driver is available, my sensor driver sends the current position to the PWM driver (altered), then it will send to the motor directly (no need to user space intervention in driving PWM), But controlling through application in userspace like start/stop/speed etc. But I have not implemented and tested this. -- Regards Jeshwanth Kumar N K Bangalore, India
My case was: I have a hall sensor connected to Beaglebone black, And Userspace needed a wakeup once the interrupt occur (example: every rising edge of GPIO). Before that, the program will register (ioctl) the User space task pointer with my kernel module, then my kernel module start sending signal for every interrupt occur. We can consider roughly around 100 to 200 interrupts per second maximum. ( I have not done this, but may be we can consider kernel will get notified when userspace program stops. so that it will not send any signal). So for this case, any other alternative
Once kernel gets interrupt, it can use netlink to notify user space, if you are using Android, it is using UEVENT.
2014-10-08 0:39 GMT-07:00 manty kuma <mantykuma@gmail.com>:
Hi, I want a user process to be notified on device wakeup so that I can print some related information.
Which framework to use for this?(events, .. ??)
You can use netlink and uevent to do this job. But just as Greg has pointed out, if your device notify frequently, your system will get slow down obviously.
One idea I get is to log the info into <debugfs> and poll(implement my poll) on it for data. This is my last option.
Are there any better ways?
Best Regards, Manty
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Hi All, Thank you for the replies. I understand that I can use netlink sockets. Also, i have gone through various other possible ways : http://people.ee.ethz.ch/~arkeller/linux/kernel_user_space_howto.html I am looking for a simpler solution which uses existing information of sys entries. That is, I am looking for a sys entry which is incremented for every device wakeup or some other sys entry that I can use to get notified on wakeup. Greg,
Really? My device can "wakeup" thousands of times a second, what are you going to do with that type of information?
I am talking of device as a whole not individual devices in the device. In kernel log, we can see a print stating "PM: suspend of devices complete after xxx msecs" --> *Prints from kernel/kernel/power/main.c* Similarly I get a print for resume stating "PM: resume of devices complete after xxx msecs" --> *Prints from kernel/kernel/power/main.c* Ideally after the above print of resume i want my stats to be printed.. Programatically after dpm_resume_end(). Best Regards, Manty On Thu, Oct 9, 2014 at 3:30 AM, Jinqiang Zeng <jinqiangzeng@gmail.com> wrote:
2014-10-08 0:39 GMT-07:00 manty kuma <mantykuma@gmail.com>:
Hi, I want a user process to be notified on device wakeup so that I can print some related information.
Which framework to use for this?(events, .. ??)
You can use netlink and uevent to do this job.
But just as Greg has pointed out, if your device notify frequently, your system will get slow down obviously.
One idea I get is to log the info into <debugfs> and poll(implement my
poll)
on it for data. This is my last option.
Are there any better ways?
Best Regards, Manty
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
participants (7)
-
buyitian -
Greg KH -
Greg Kroah-Hartman
-
Jeshwanth Kumar N K -
Jinqiang Zeng -
Kristof Provost -
manty kuma