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Today's Topics:
1. Openmoko Bug #2366: Missing accelerometer events
(Openmoko Public Trac)
2. Re: Openmoko Bug #2366: Missing accelerometer events
(Openmoko Public Trac)
3. Re: Openmoko Bug #2366: Missing accelerometer events
(Openmoko Public Trac)
4. Re: Openmoko Bug #2366: Missing accelerometer events
(Openmoko Public Trac)
--- Begin Message ---
#2366: Missing accelerometer events
---------------------+------------------------------------------------------
Reporter: mkburza | Owner: openmoko-kernel
Type: defect | Status: new
Priority: highest | Milestone: stable-kernel-2009.1
Component: kernel | Version: unspecified
Severity: normal | Keywords:
Haspatch: 0 | Blockedby:
Estimated: | Patchreview:
Blocking: | Reproducible:
---------------------+------------------------------------------------------
I am using following version of the software:
http://build.shr-project.org/shr-unstable/images/om-gta02/shr-full-eglibc-
ipk--20100828-om-gta02.rootfs.jffs2
http://build.shr-project.org/shr-unstable/images/om-
gta02/uImage-2.6.32.21-oe3.3+gitr6+a9254be10ac2294ea20165a87c09ea6afcf66d94-r0
-om-gta02.bin
I read accelerometer events with following C program:
#include <stdio.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>
#include <linux/input.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <sys/times.h>
int read_all(int fd, char *buffer, int count){
int got = 0;
while(got != count) {
int result = read(fd, buffer + got, count - got);
if(result > 0){
got += result;
}
}
return got;
}
int grab = 2;
int main(int argc, char *argv[]){
int fd, i;
struct input_event ev[128];
if((fd = open("/dev/input/event3", O_RDONLY)) == -1){
perror("Open");
return 1;
}
int ioret = ioctl(fd, EVIOCGRAB, &grab); // Without this I also get
missing events
if(-1 == ioret){ // but I was hoping it would help
perror("ioctl()"); //
} //
int got = read_all(fd, (char*)ev, 128 * sizeof(struct input_event));
close(fd);
for(i = 0; i < 128; i++){
printf("type:%u code:%u value:%d\n", ev[i].type, ev[i].code,
ev[i].value);
}
return 0;
}
As you can see I first collect all the events and then I print them out to
avoid any waiting time which would result in missing events.
In principle if everything is fine I would expect such pattern on the
output:
type:3 code:0 value:[whateverX]
type:3 code:1 value:[whateverY]
type:3 code:2 value:[whateverZ]
type:0 code:0 value:0
Here is a fragment of real output:
type:3 code:0 value:-284
type:3 code:1 value:355
type:3 code:2 value:497
type:0 code:0 value:0
type:3 code:0 value:71
type:3 code:1 value:0
type:3 code:2 value:923
type:0 code:0 value:0
type:3 code:0 value:0
type:0 code:0 value:0
type:3 code:0 value:71
type:0 code:0 value:0
type:3 code:0 value:0
type:0 code:0 value:0
type:3 code:0 value:71
type:3 code:2 value:994
type:0 code:0 value:0
type:3 code:2 value:923
type:0 code:0 value:0
type:3 code:2 value:994
type:0 code:0 value:0
type:3 code:2 value:923
type:0 code:0 value:0
type:3 code:0 value:0
type:3 code:2 value:994
type:0 code:0 value:0
type:3 code:2 value:923
type:0 code:0 value:0
type:3 code:0 value:71
type:0 code:0 value:0
type:3 code:0 value:0
type:3 code:2 value:994
type:0 code:0 value:0
type:3 code:0 value:71
type:3 code:2 value:923
type:0 code:0 value:0
type:3 code:2 value:994
type:0 code:0 value:0
type:3 code:2 value:923
type:0 code:0 value:0
type:3 code:0 value:0
type:0 code:0 value:0
type:3 code:0 value:71
type:0 code:0 value:0
As you can see the pattern of having three consecutive events reporting
each of the axis followed by sync event is broken and often events for
some x, y or z are missing.
I checked how the program behaves if I collect the events for several
minutes (it is the same with randomly missing events). I tried to increase
the priority with nice to see if that helps (thinking that maybe the
processor is too busy) - it didn't help. I checked the CPU usage - it does
not go over 20% overall (15% for the process which reads the events).
Here is the configuration of the accelerometer:
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/sample_rate:
100
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/full_scale:
9.2
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/threshold:
0
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/duration:
0
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/dump:
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 3b
a8 95 01 13 13 01 06 82 01 e3 0e 58 00 00 00 00
20 00 a4 00 00 00 00 00 00 01 00 00 00 0d 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/wakeup_threshold:
off
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/wakeup_duration:
0
/sys/devices/platform/s3c2440-i2c/i2c-0/0-0073/spi_s3c24xx_gpio.0/spi3.0/overruns:
1
This was checked on several Freerunners and all of them behave the same.
Please let me know if you need further data/config info/etc.
Best regards,
Mark
PS: I reported this at first on SHR's trac but after they looked into it
they asked me to post it here as it concerns the kernel.
--
Ticket URL: <https://docs.openmoko.org/trac/ticket/2366>
docs.openmoko.org <http://docs.openmoko.org/trac/>
openmoko trac
--- End Message ---
--- Begin Message ---
#2366: Missing accelerometer events
---------------------+------------------------------------------------------
Reporter: mkburza | Owner: openmoko-kernel
Type: defect | Status: new
Priority: highest | Milestone: stable-kernel-2009.1
Component: kernel | Version: unspecified
Severity: normal | Keywords:
Haspatch: 0 | Blockedby:
Estimated: | Patchreview:
Blocking: | Reproducible:
---------------------+------------------------------------------------------
Comment(by neilbrown):
This is expected behaviour.
These are events that report when something changes.
If nothing changes, you don't get an event.
In particular, if the X and Y acceleration changes but the Z acceleration
doesn't, you get
X and Y events but not Z events. You need to think of then as 3 separate
accelerometers which report separately.
If you want to find the current value of any of the three, you can either
remember the last time it reported, or use the EVIOCGABS ioctl (See
/usr/include/linux/input.h for details)
--
Ticket URL: <https://docs.openmoko.org/trac/ticket/2366#comment:1>
docs.openmoko.org <http://docs.openmoko.org/trac/>
openmoko trac
--- End Message ---
--- Begin Message ---
#2366: Missing accelerometer events
---------------------+------------------------------------------------------
Reporter: mkburza | Owner: openmoko-kernel
Type: defect | Status: new
Priority: highest | Milestone: stable-kernel-2009.1
Component: kernel | Version: unspecified
Severity: normal | Keywords:
Haspatch: 0 | Blockedby:
Estimated: | Patchreview:
Blocking: | Reproducible:
---------------------+------------------------------------------------------
Comment(by mkburza):
Thanks for such a quick reply!!!
> This is expected behaviour.
> These are events that report when something changes.
I see, if that is the expected behavior then that's something I can live
with. And thanks for the suggestion about the EVIOCGABS - I might use that
one!
One more question though before I let go of that matter - I do observe
that when the phone lies flat on a table X is updated the least, Y about
twice as often and Z at least three times as often as X.
Even if I would assume that the measurement gets noisier due to the
gravity force acting along the Z axis (which I do not know if I can
assume) this still does not explain why is Y updated more frequently than
X (and it is a behavior I consistently observe on multiple Freerunners).
Do you have any (possible) explanation for that?
--
Ticket URL: <https://docs.openmoko.org/trac/ticket/2366#comment:2>
docs.openmoko.org <http://docs.openmoko.org/trac/>
openmoko trac
--- End Message ---
--- Begin Message ---
#2366: Missing accelerometer events
---------------------+------------------------------------------------------
Reporter: mkburza | Owner: openmoko-kernel
Type: defect | Status: new
Priority: highest | Milestone: stable-kernel-2009.1
Component: kernel | Version: unspecified
Severity: normal | Keywords:
Haspatch: 0 | Blockedby:
Estimated: | Patchreview:
Blocking: | Reproducible:
---------------------+------------------------------------------------------
Comment(by neilbrown):
No, I cannot explain that.
Every time the accelerometers report a sample - which is 100 times per
second I think - those
samples are passed to the 'input' layer in Linux. This input layer
removes the duplicates.
So it might be somehow related to noise, whether physical or electrical.
I have no idea why
X is most noisy and Z is least noisy.
--
Ticket URL: <https://docs.openmoko.org/trac/ticket/2366#comment:3>
docs.openmoko.org <http://docs.openmoko.org/trac/>
openmoko trac
--- End Message ---
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