issues dealing with kobjects
Hello all,
I am facing a small issue dealing with kobjects.
I am writing a simple i2c driver for which I would like to export a few
sysfs attributes(files).
The files are many, so I've decided to pack them into a directory in
sysfs (inside the i2c device) and so I thought of kobjects.
My private data struture is something like this :
struct my_private {
struct i2c_client *client;
...
struct kobject kobj;
};
In my probe function, I am doing something like this :
int my_probe(struct i2c_client *client, ...)
{
struct my_private *dev;
dev = devm_kzalloc(...);
pr_info(%x, dev);/* The address that I got is
: 0xdbf94210 */
/* Init. and add kboject */
kobject_init(dev-kobj, client-dev.kobj.ktype);
kobject_add(dev-kobj, client-dev.kobj, my_dir);
/* Export sysfs group */
sysfs_create_group(dev-kobj, my_attr_grp);
}
My show function for one of the attribute is something like this :
ssize_t show(struct kobject *kobj, ... )
{
struct my_private *dev = container_of(kobj, struct my_private, kobj);
pr_info(%x, dev);/* The address that I got is
: 0xdbf94208 */
}
I tried to probe and remove the device mutilple times. Every time I am
getting a difference of 2bytes for the 'dev'
pointer between probe and show functions.
Can anyone explain me where am I going wrong or is there any better way
to create directories in sysfs?
I am building this module against 3.13.2 kernel.
Thank you.
Raghavendra.
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Re: issues dealing with kobjects
You have two *different* local pointer with same name.
On Fri, Jun 20, 2014 at 2:01 PM, Raghavendra ar...@cdac.in wrote:
Hello all,
I am facing a small issue dealing with kobjects.
I am writing a simple i2c driver for which I would like to export a few
sysfs attributes(files).
The files are many, so I've decided to pack them into a directory in
sysfs (inside the i2c device) and so I thought of kobjects.
My private data struture is something like this :
struct my_private {
struct i2c_client *client;
...
struct kobject kobj;
};
In my probe function, I am doing something like this :
int my_probe(struct i2c_client *client, ...)
{
struct my_private *dev;
dev = devm_kzalloc(...);
pr_info(%x, dev);/* The address that I got is
: 0xdbf94210 */
/* Init. and add kboject */
kobject_init(dev-kobj, client-dev.kobj.ktype);
kobject_add(dev-kobj, client-dev.kobj, my_dir);
/* Export sysfs group */
sysfs_create_group(dev-kobj, my_attr_grp);
}
My show function for one of the attribute is something like this :
ssize_t show(struct kobject *kobj, ... )
{
struct my_private *dev = container_of(kobj, struct my_private, kobj);
pr_info(%x, dev);/* The address that I got is
: 0xdbf94208 */
}
I tried to probe and remove the device mutilple times. Every time I am
getting a difference of 2bytes for the 'dev'
pointer between probe and show functions.
Can anyone explain me where am I going wrong or is there any better way
to create directories in sysfs?
I am building this module against 3.13.2 kernel.
Thank you.
Raghavendra.
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Re: issues dealing with kobjects
On Friday 20 June 2014 11:31 AM, Raghavendra wrote:
Hello all,
I am facing a small issue dealing with kobjects.
I am writing a simple i2c driver for which I would like to export a few
sysfs attributes(files).
The files are many, so I've decided to pack them into a directory in
sysfs (inside the i2c device) and so I thought of kobjects.
My private data struture is something like this :
struct my_private {
struct i2c_client *client;
...
struct kobject kobj;
};
In my probe function, I am doing something like this :
int my_probe(struct i2c_client *client, ...)
{
struct my_private *dev;
dev = devm_kzalloc(...);
pr_info(%x, dev);/* The address that I got is
: 0xdbf94210 */
/* Init. and add kboject */
kobject_init(dev-kobj, client-dev.kobj.ktype);
kobject_add(dev-kobj, client-dev.kobj, my_dir);
/* Export sysfs group */
sysfs_create_group(dev-kobj, my_attr_grp);
}
My show function for one of the attribute is something like this :
ssize_t show(struct kobject *kobj, ... )
{
struct my_private *dev = container_of(kobj, struct my_private, kobj);
pr_info(%x, dev);/* The address that I got is
: 0xdbf94208 */
}
I tried to probe and remove the device mutilple times. Every time I am
getting a difference of 2bytes for the 'dev'
pointer between probe and show functions.
Can anyone explain me where am I going wrong or is there any better way
to create directories in sysfs?
I am building this module against 3.13.2 kernel.
Thank you.
Raghavendra.
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I guess I've solved the issue. Now the code looks something like this :
struct my_private {
struct i2c_client *client;
...
struct kobject *kobj; /* Converted variable to ptr */
};
int my_probe(struct i2c_client *client, ...)
{
struct my_private *dev;
dev = devm_kzalloc(...);
/* Replaced with kobject_init and kobject_add calls */
dev-kobj = kobject_create_and_add(my_dir, client-dev.kobj);
/* Export sysfs group */
sysfs_create_group(dev-kobj, my_attr_grp);
}
ssize_t show(struct kobject *kobj, ... )
{
struct device *i2cdev = kobj_to_dev(kobj-parent);
struct i2c_client *client = to_i2c_client(i2cdev);
struct my_private *dev = i2c_get_clientdata(client);
}
This approach worked, but there's a lot of redundancy in the show() function,
just to obtain the pointer to the private data.
I would be glad if anyone suggested any better approach to create and manage
sysfs directories and attribute groups.
Thank you,
Raghavendra
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Understanding #ifdef in .h files
Hi,
I try to understand how #ifdef in .h files works.
I read Greg Kroah-Hartman's Coding style paper
http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/mgp00031.html
And as he says, i try to do a simple example but it does not work. I
try with a small piece of C outside the kernel. I have 3 files.
test_ifdef.h:
#ifdef TEST_FUNCTION
void test(int *value);
#else
static inline void test(int *value) { }
#endif
test_ifdef.c:
#include test_ifdef.h
void test(int *value)
{
*value += 1;
}
main.c:
#include stdio.h
#include test_ifdef.h
int main(int argc, char *argv[])
{
int i = 3;
printf(i = %d\n, i);
test(i);
printf(i = %d\n, i);
return 0;
}
And when i compile:
$ gcc -Wall -g main.c test_ifdef.c -o test_ifdef -DTEST_FUNCTION
$ ./test_ifdef
i = 3
i = 4
$ gcc -Wall -g main.c test_ifdef.c -o test_ifdef
test_ifdef.c:14:6: error: redefinition of ‘test’
void test(int *value)
^
In file included from test_ifdef.c:12:0:
test_ifdef.h:17:20: note: previous definition of ‘test’ was here
static inline void test(int *value) { }
^
$
I understand why it does not compile. But:
- How it can work in the kernel code ?
- Is-it possible to do this in code outside the kernel ?
Thank you.
Harold
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Re: Understanding #ifdef in .h files
Hi Harold
On 6/20/14, Harold André harold.an...@gmx.fr wrote:
Hi,
I try to understand how #ifdef in .h files works.
I read Greg Kroah-Hartman's Coding style paper
http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/mgp00031.html
And as he says, i try to do a simple example but it does not work. I
try with a small piece of C outside the kernel. I have 3 files.
test_ifdef.h:
You say here you will define the function else where if TEST_FUNCTION is defined
#ifdef TEST_FUNCTION
void test(int *value);
#else
static inline void test(int *value) { }
#endif
test_ifdef.c:
#include test_ifdef.h
But here you do on and define it any way. You must stick to the rule
you created earlier. If you are defining it here then this must also
be under the test of ifdef TEST_FUNCTION
void test(int *value)
{
*value += 1;
}
main.c:
#include stdio.h
#include test_ifdef.h
int main(int argc, char *argv[])
{
int i = 3;
printf(i = %d\n, i);
test(i);
printf(i = %d\n, i);
return 0;
}
And when i compile:
$ gcc -Wall -g main.c test_ifdef.c -o test_ifdef -DTEST_FUNCTION
$ ./test_ifdef
i = 3
i = 4
$ gcc -Wall -g main.c test_ifdef.c -o test_ifdef
test_ifdef.c:14:6: error: redefinition of ‘test’
void test(int *value)
^
In file included from test_ifdef.c:12:0:
test_ifdef.h:17:20: note: previous definition of ‘test’ was here
static inline void test(int *value) { }
^
$
I understand why it does not compile. But:
- How it can work in the kernel code ?
- Is-it possible to do this in code outside the kernel ?
Thank you.
Harold
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TASK05
Hello, I am stuck on Task05. Can you help me with more pointers for this task ? So I can read and understand and write my own code. I am sorry, I am lazy. I tried following LDD chapter mentioned but I am not able to get it into the code, so as to get it working. Either I am not trying hard enough or I am not understanding it as I am lacking some basics to get right clarity from reading chapter 14 of LDD. Can somebody give a push to my stuck threads so I get it right? Thanks in advance. Sorry if I sound vague. -- cheers Akam ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: TASK05
On Fri, Jun 20, 2014 at 5:32 PM, Akam azurelus...@gmail.com wrote: Hello, I am stuck on Task05. Can you help me with more pointers for this task ? So I can read and understand and write my own code. I am sorry, I am lazy. I tried following LDD chapter mentioned but I am not able to get it into the code, so as to get it working. Either I am not trying hard enough or I am not understanding it as I am lacking some basics to get right clarity from reading chapter 14 of LDD. Can somebody give a push to my stuck threads so I get it right? Thanks in advance. Sorry if I sound vague. Hi Akram, The rule for the Challenge says you really should be doing your own work , so you really should be doing your own work . shouldn't you ? And besides task 5 is very easy ... although I was stuck with it for almost 3 weeks :) , but still its very easy .. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: TASK05
El 20/06/2014 14:02, Akam azurelus...@gmail.com escribió: Hello, I am stuck on Task05. Can you help me with more pointers for this task ? So I can read and understand and write my own code. I am sorry, I am lazy. I tried following LDD chapter mentioned but I am not able to get it into the code, so as to get it working. Either I am not trying hard enough or I am not understanding it as I am lacking some basics to get right clarity from reading chapter 14 of LDD. Can somebody give a push to my stuck threads so I get it right? Thanks in advance. Sorry if I sound vague. Hi Akam, Since this is a challenge, you're supposed to find your own solutions. Little was pretty specific about this. Just relax. Leave the computer untouched for a couple of days and forget the challenge. Then try to tackle it again. Have another read to the ldd and search in the kernel for similar code (that can give you a good hint). If you don't get it right the first time, don't despair, do one step at a time until you are done. Good luck! -- cheers Akam ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: TASK05
Hello, Even i found it difficult at first, read online , search a bit. it's better when you do it yourself :D Regards, Karthik On Fri, Jun 20, 2014 at 5:32 PM, Akam azurelus...@gmail.com wrote: Hello, I am stuck on Task05. Can you help me with more pointers for this task ? So I can read and understand and write my own code. I am sorry, I am lazy. I tried following LDD chapter mentioned but I am not able to get it into the code, so as to get it working. Either I am not trying hard enough or I am not understanding it as I am lacking some basics to get right clarity from reading chapter 14 of LDD. Can somebody give a push to my stuck threads so I get it right? Thanks in advance. Sorry if I sound vague. -- cheers Akam ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: TASK05
On Fri, Jun 20, 2014 at 5:41 PM, Sudip Mukherjee sudipm.mukher...@gmail.com wrote: On Fri, Jun 20, 2014 at 5:32 PM, Akam azurelus...@gmail.com wrote: Hello, I am stuck on Task05. Can you help me with more pointers for this task ? So I can read and understand and write my own code. I am sorry, I am lazy. I tried following LDD chapter mentioned but I am not able to get it into the code, so as to get it working. Either I am not trying hard enough or I am not understanding it as I am lacking some basics to get right clarity from reading chapter 14 of LDD. Can somebody give a push to my stuck threads so I get it right? Thanks in advance. Sorry if I sound vague. Hi Akram, The rule for the Challenge says you really should be doing your own work , so you really should be doing your own work . shouldn't you ? And besides task 5 is very easy ... although I was stuck with it for almost 3 weeks :) , but still its very easy .. And if you think you are lacking the basics, I will advice you to go back to the basics first. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: TASK05
So I can read and understand and write my own code. I think I already mentioned it, write my own code . I take this as, I was vague in the email and will correct myself next time Thanks Fernando, that’s conducive. Thanks all. PS BTW My name is AKAM. On Fri, Jun 20, 2014 at 5:44 PM, Sudip Mukherjee sudipm.mukher...@gmail.com wrote: On Fri, Jun 20, 2014 at 5:41 PM, Sudip Mukherjee sudipm.mukher...@gmail.com wrote: On Fri, Jun 20, 2014 at 5:32 PM, Akam azurelus...@gmail.com wrote: Hello, I am stuck on Task05. Can you help me with more pointers for this task ? So I can read and understand and write my own code. I am sorry, I am lazy. I tried following LDD chapter mentioned but I am not able to get it into the code, so as to get it working. Either I am not trying hard enough or I am not understanding it as I am lacking some basics to get right clarity from reading chapter 14 of LDD. Can somebody give a push to my stuck threads so I get it right? Thanks in advance. Sorry if I sound vague. Hi Akram, The rule for the Challenge says you really should be doing your own work , so you really should be doing your own work . shouldn't you ? And besides task 5 is very easy ... although I was stuck with it for almost 3 weeks :) , but still its very easy .. And if you think you are lacking the basics, I will advice you to go back to the basics first. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- easy is right begin right and you're easy continue easy and you're right the right way to go easy is to forget the right way and forget that the going is easy ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Understanding #ifdef in .h files
On Fri, Jun 20, 2014 at 6:29 PM, Harold André harold.an...@gmx.fr wrote:
Le Fri, 20 Jun 2014 16:36:58 +0530,
Pranay Srivastava pran...@gmail.com a écrit :
You say here you will define the function else where if TEST_FUNCTION
is defined
#ifdef TEST_FUNCTION
void test(int *value);
#else
static inline void test(int *value) { }
#endif
test_ifdef.c:
#include test_ifdef.h
But here you do on and define it any way. You must stick to the rule
you created earlier. If you are defining it here then this must also
be under the test of ifdef TEST_FUNCTION
void test(int *value)
{
*value += 1;
}
Thank you Pranay for your answer. I understand this now.
But when i look at the kernel code, i don't see ifdef test around the
definition of the function. For example, i look for the function
hiddev_hid_event:
In include/linux/hiddev.h:
#ifdef CONFIG_USB_HIDDEV
...
void hiddev_hid_event(struct hid_device *hid, struct hid_field *field,
struct hid_usage *usage, __s32 value);
...
#else
...
static inline void hiddev_hid_event(struct hid_device *hid, struct
hid_field *field, struct hid_usage *usage, __s32 value) { }
...
#endif
In drivers/hid/usbhid/hiddev.c:
/*
* This is where hid.c calls into hiddev to pass an event that occurred
over
That's right but the magic doesn't happen here :-)
if you see usbhid/Makefile you'll understand what I mean :-). If not ,
please do ask.
* the interrupt pipe
*/
void hiddev_hid_event(struct hid_device *hid, struct hid_field *field,
struct hid_usage *usage, __s32 value)
{
unsigned type = field-report_type;
struct hiddev_usage_ref uref;
uref.report_type =
(type == HID_INPUT_REPORT) ? HID_REPORT_TYPE_INPUT :
((type == HID_OUTPUT_REPORT) ? HID_REPORT_TYPE_OUTPUT :
((type == HID_FEATURE_REPORT) ? HID_REPORT_TYPE_FEATURE :
0)); uref.report_id = field-report-id;
uref.field_index = field-index;
uref.usage_index = (usage - field-usage);
uref.usage_code = usage-hid;
uref.value = value;
hiddev_send_event(hid, uref);
}
EXPORT_SYMBOL_GPL(hiddev_hid_event);
And in drivers/hid/hid-core.c:
...
if (hid-claimed HID_CLAIMED_INPUT)
hidinput_hid_event(hid, field, usage, value);
if (hid-claimed HID_CLAIMED_HIDDEV interrupt
hid-hiddev_hid_event)
hid-hiddev_hid_event(hid, field, usage, value);
...
If i'm right. The function hiddev_hid_event is always defined in
hiddev.c whatever CONFIG_USB_HIDDEV is defined or not ?
How is it possible ?
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Re: Understanding #ifdef in .h files
Le Fri, 20 Jun 2014 16:36:58 +0530,
Pranay Srivastava pran...@gmail.com a écrit :
You say here you will define the function else where if TEST_FUNCTION
is defined
#ifdef TEST_FUNCTION
void test(int *value);
#else
static inline void test(int *value) { }
#endif
test_ifdef.c:
#include test_ifdef.h
But here you do on and define it any way. You must stick to the rule
you created earlier. If you are defining it here then this must also
be under the test of ifdef TEST_FUNCTION
void test(int *value)
{
*value += 1;
}
Thank you Pranay for your answer. I understand this now.
But when i look at the kernel code, i don't see ifdef test around the
definition of the function. For example, i look for the function
hiddev_hid_event:
In include/linux/hiddev.h:
#ifdef CONFIG_USB_HIDDEV
...
void hiddev_hid_event(struct hid_device *hid, struct hid_field *field,
struct hid_usage *usage, __s32 value);
...
#else
...
static inline void hiddev_hid_event(struct hid_device *hid, struct
hid_field *field, struct hid_usage *usage, __s32 value) { }
...
#endif
In drivers/hid/usbhid/hiddev.c:
/*
* This is where hid.c calls into hiddev to pass an event that occurred
over
* the interrupt pipe
*/
void hiddev_hid_event(struct hid_device *hid, struct hid_field *field,
struct hid_usage *usage, __s32 value)
{
unsigned type = field-report_type;
struct hiddev_usage_ref uref;
uref.report_type =
(type == HID_INPUT_REPORT) ? HID_REPORT_TYPE_INPUT :
((type == HID_OUTPUT_REPORT) ? HID_REPORT_TYPE_OUTPUT :
((type == HID_FEATURE_REPORT) ? HID_REPORT_TYPE_FEATURE :
0)); uref.report_id = field-report-id;
uref.field_index = field-index;
uref.usage_index = (usage - field-usage);
uref.usage_code = usage-hid;
uref.value = value;
hiddev_send_event(hid, uref);
}
EXPORT_SYMBOL_GPL(hiddev_hid_event);
And in drivers/hid/hid-core.c:
...
if (hid-claimed HID_CLAIMED_INPUT)
hidinput_hid_event(hid, field, usage, value);
if (hid-claimed HID_CLAIMED_HIDDEV interrupt
hid-hiddev_hid_event)
hid-hiddev_hid_event(hid, field, usage, value);
...
If i'm right. The function hiddev_hid_event is always defined in
hiddev.c whatever CONFIG_USB_HIDDEV is defined or not ?
How is it possible ?
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Re: How to get the average/max process scheduling latency
Thanks for the answer. Do you know any tool/software to retrieve the average latency for a specific program on a specific platform. This is to modelize the application rate for data processing. 2014-06-19 22:16 GMT+02:00 valdis.kletni...@vt.edu: On Mon, 16 Jun 2014 18:23:56 +0200, Teto said: I could not find an answer yet. I've found that on latest kernel latency is on average around 3us with a max at 64us (I consider a moderate load). Is that correct ? Depends on your hardware and system load. I'd hardly expect the same numbers from a busy Beaglebone or Raspberry Pi as from a idle high-end Intel i7 system (And things like processors that drop into sleep states when idle, with a latency hit to wake up, just add to the confusion) ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Understanding #ifdef in .h files
Le Fri, 20 Jun 2014 18:44:35 +0530,
Pranay Srivastava pran...@gmail.com a écrit :
On Fri, Jun 20, 2014 at 6:29 PM, Harold André harold.an...@gmx.fr
wrote:
Le Fri, 20 Jun 2014 16:36:58 +0530,
Pranay Srivastava pran...@gmail.com a écrit :
You say here you will define the function else where if
TEST_FUNCTION is defined
#ifdef TEST_FUNCTION
void test(int *value);
#else
static inline void test(int *value) { }
#endif
test_ifdef.c:
#include test_ifdef.h
But here you do on and define it any way. You must stick to the
rule you created earlier. If you are defining it here then this
must also be under the test of ifdef TEST_FUNCTION
void test(int *value)
{
*value += 1;
}
Thank you Pranay for your answer. I understand this now.
But when i look at the kernel code, i don't see ifdef test around
the definition of the function. For example, i look for the function
hiddev_hid_event:
In include/linux/hiddev.h:
#ifdef CONFIG_USB_HIDDEV
...
void hiddev_hid_event(struct hid_device *hid, struct hid_field
*field, struct hid_usage *usage, __s32 value);
...
#else
...
static inline void hiddev_hid_event(struct hid_device *hid, struct
hid_field *field, struct hid_usage *usage, __s32 value) { }
...
#endif
In drivers/hid/usbhid/hiddev.c:
/*
* This is where hid.c calls into hiddev to pass an event that
occurred over
That's right but the magic doesn't happen here :-)
if you see usbhid/Makefile you'll understand what I mean :-). If not ,
please do ask.
Ah yes !! Ok, i understand !! ;-)
Thank Pranay for sharing your knowledge !
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Re: issues dealing with kobjects
On Fri, Jun 20, 2014 at 11:31:03AM +0530, Raghavendra wrote: Hello all, I am facing a small issue dealing with kobjects. I am writing a simple i2c driver for which I would like to export a few sysfs attributes(files). Please don't, unless these attributes are something that all other i2c drivers export and are documented in Documentation/ABI/ The files are many, so I've decided to pack them into a directory in sysfs (inside the i2c device) and so I thought of kobjects. No, please never use raw kobjects in a driver, use the driver core functions instead. You can have an attribute group that is associated with your driver or device, and the driver core will automatically create the files for you (in a subdir if you want it), in a race-free manner. Please use that interface instead. thanks, greg k-h ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: How to get the average/max process scheduling latency
On Fri, 20 Jun 2014 15:36:47 +0200, Teto said: Do you know any tool/software to retrieve the average latency for a specific program on a specific platform. This is to modelize the application rate for data processing. You need to add while running under a specific application load, because latencies can be different if you're under high enough load to keep the CPU running at high clock rate, versus if it's dropping to a low clock rate and then into a sleep state The 'latencytop' utility may help here. pgp92z76I_xzN.pgp Description: PGP signature ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
