Yellow wrote:

> now, to my real problem: I must record some sound, and then play it!
> since in LInux everything is a file, I'm able to do it by means of
> /dev/dsp. that's why I asked abou t how to work with regular files. but
> I don't know if this way of accessing devices hold for modules. and I
> can't open that file!

No; that way of accessing files is not used from within the kernel
(though it is possible to access regular files). Why do you think you
ought to do this from within a kernel module?

The usual way of doing such things is to write a driver -- which may or
may not be contained within a loadable kernel module -- that interfaces
to a particular type of device and provides the ability to read from or
write to the device (or both). Then one uses an application
(non-kernel) program to read data from one device and write it to
another (or from a device to a file, or from a file to a device, and so
forth). "Everything is a file" in Linux only because there is a driver
for each device that makes it look that way.

GH

Try using these calls,
filp_open and filp_close
regards,
samir
Yellow wrote:
> hi there!
>
> I have just started studying the linux kernel, version 2.6. i read some
> manuals, howtos, have already made some really simple modules, but when
> I tried to do a little more complex work, I stumbled across some
> dificulties.
> well, what I want to is a kernel module that opens a regular file,
> writes something to it, and closes it. easy, isn't it? I also thought
> that
>
> but then I tried making a simple open over the file, but the module
> complains it can't find the symbols open, close and write. Is there
> anything unusual I must do to work with files in the kernel? none of
> the manuals I read mentioned how to open and do some I/O over it.
>
> now, to my real problem: I must record some sound, and then play it!
> since in LInux everything is a file, I'm able to do it by means of
> /dev/dsp. that's why I asked abou t how to work with regular files. but
> I don't know if this way of accessing devices hold for modules. and I
> can't open that file!
>
> I looked at /proc/kallsyms, and open is there. I don't have a clue why
> the module complains it couldn't find the open.
>
> thanks for any help you could provide, and sorry for such noob question

Yellow wrote:

> hi there!
>
> I have just started studying the linux kernel, version 2.6. i read some
> manuals, howtos, have already made some really simple modules, but when
> I tried to do a little more complex work, I stumbled across some
> dificulties.
> well, what I want to is a kernel module that opens a regular file,
> writes something to it, and closes it. easy, isn't it? I also thought
> that
>
> but then I tried making a simple open over the file, but the module
> complains it can't find the symbols open, close and write. Is there
Are you doing OPEN(filename, flags)?
> anything unusual I must do to work with files in the kernel? none of
> the manuals I read mentioned how to open and do some I/O over it.
>
> now, to my real problem: I must record some sound, and then play it!
> since in LInux everything is a file, I'm able to do it by means of
> /dev/dsp. that's why I asked abou t how to work with regular files. but
> I don't know if this way of accessing devices hold for modules. and I
> can't open that file!
>
> I looked at /proc/kallsyms, and open is there. I don't have a clue why
> the module complains it couldn't find the open.
Kernel opens the files with sys_open, similary sys_close, sys_read,
sys_write and so on.
>
> thanks for any help you could provide, and sorry for such noob question

thanks for all the replies. I tried using sys_open, and "aparently" I
could open the file, but I couldn't write or read it using sys_write or
sys_read. Linux complains it can't find the sys_read and sys_write
symbols.
I also tried using filp_open and filp_open, but got a segmentation
fault .
here's my code, and what I want to do first:

int init_module(void)
{
int fd;
printk(KERN_ALERT "module loaded\n");
fd = open("/home/alisson/texte.txt", 02);
if(fd ==-1)
printk(KERN_ALERT "error opening file");
/* write something here */
close(fd);
return 0;
}

but what I'd like to know is: can I use the sound card the same way I
use it in user space programs? like reading and opening a file? my
final goal is record some sound from the microphone for 3 seconds, and
then play it.

thanks


miline wrote:
> Yellow wrote:
>
> > hi there!
> >
> > I have just started studying the linux kernel, version 2.6. i read some
> > manuals, howtos, have already made some really simple modules, but when
> > I tried to do a little more complex work, I stumbled across some
> > dificulties.
> > well, what I want to is a kernel module that opens a regular file,
> > writes something to it, and closes it. easy, isn't it? I also thought
> > that
> >
> > but then I tried making a simple open over the file, but the module
> > complains it can't find the symbols open, close and write. Is there
> Are you doing OPEN(filename, flags)?
> > anything unusual I must do to work with files in the kernel? none of
> > the manuals I read mentioned how to open and do some I/O over it.
> >
> > now, to my real problem: I must record some sound, and then play it!
> > since in LInux everything is a file, I'm able to do it by means of
> > /dev/dsp. that's why I asked abou t how to work with regular files. but
> > I don't know if this way of accessing devices hold for modules. and I
> > can't open that file!
> >
> > I looked at /proc/kallsyms, and open is there. I don't have a clue why
> > the module complains it couldn't find the open.
> Kernel opens the files with sys_open, similary sys_close, sys_read,
> sys_write and so on.
> >
> > thanks for any help you could provide, and sorry for such noob question

oh, sorry, but maybe I didn't make myself clear last post: what I'd
like to know is how can I use the soundcard in kernel space. if it
doesn't involve any operations with device files, please, don't stick
to the reading/writing to file issue.
regards

Yellow wrote:
> thanks for all the replies. I tried using sys_open, and "aparently" I
> could open the file, but I couldn't write or read it using sys_write or
> sys_read. Linux complains it can't find the sys_read and sys_write
> symbols.
> I also tried using filp_open and filp_open, but got a segmentation
> fault .
> here's my code, and what I want to do first:
>
> int init_module(void)
> {
> int fd;
> printk(KERN_ALERT "module loaded\n");
> fd = open("/home/alisson/texte.txt", 02);
> if(fd ==-1)
> printk(KERN_ALERT "error opening file");
> /* write something here */
> close(fd);
> return 0;
> }
>
> but what I'd like to know is: can I use the sound card the same way I
> use it in user space programs? like reading and opening a file? my
> final goal is record some sound from the microphone for 3 seconds, and
> then play it.
>
> thanks
>
>
> miline wrote:
> > Yellow wrote:
> >
> > > hi there!
> > >
> > > I have just started studying the linux kernel, version 2.6. i read some
> > > manuals, howtos, have already made some really simple modules, but when
> > > I tried to do a little more complex work, I stumbled across some
> > > dificulties.
> > > well, what I want to is a kernel module that opens a regular file,
> > > writes something to it, and closes it. easy, isn't it? I also thought
> > > that
> > >
> > > but then I tried making a simple open over the file, but the module
> > > complains it can't find the symbols open, close and write. Is there
> > Are you doing OPEN(filename, flags)?
> > > anything unusual I must do to work with files in the kernel? none of
> > > the manuals I read mentioned how to open and do some I/O over it.
> > >
> > > now, to my real problem: I must record some sound, and then play it!
> > > since in LInux everything is a file, I'm able to do it by means of
> > > /dev/dsp. that's why I asked abou t how to work with regular files. but
> > > I don't know if this way of accessing devices hold for modules. and I
> > > can't open that file!
> > >
> > > I looked at /proc/kallsyms, and open is there. I don't have a clue why
> > > the module complains it couldn't find the open.
> > Kernel opens the files with sys_open, similary sys_close, sys_read,
> > sys_write and so on.
> > >
> > > thanks for any help you could provide, and sorry for such noob question

There is one link in the reference link at this place, just what you
want:how to read file from kernel:

http://www.rtprogramming.blogspot.com/




Yellow wrote:
> oh, sorry, but maybe I didn't make myself clear last post: what I'd
> like to know is how can I use the soundcard in kernel space. if it
> doesn't involve any operations with device files, please, don't stick
> to the reading/writing to file issue.
> regards
>
> Yellow wrote:
> > thanks for all the replies. I tried using sys_open, and "aparently" I
> > could open the file, but I couldn't write or read it using sys_write or
> > sys_read. Linux complains it can't find the sys_read and sys_write
> > symbols.
> > I also tried using filp_open and filp_open, but got a segmentation
> > fault .
> > here's my code, and what I want to do first:
> >
> > int init_module(void)
> > {
> > int fd;
> > printk(KERN_ALERT "module loaded\n");
> > fd = open("/home/alisson/texte.txt", 02);
> > if(fd ==-1)
> > printk(KERN_ALERT "error opening file");
> > /* write something here */
> > close(fd);
> > return 0;
> > }
> >
> > but what I'd like to know is: can I use the sound card the same way I
> > use it in user space programs? like reading and opening a file? my
> > final goal is record some sound from the microphone for 3 seconds, and
> > then play it.
> >
> > thanks
> >
> >
> > miline wrote:
> > > Yellow wrote:
> > >
> > > > hi there!
> > > >
> > > > I have just started studying the linux kernel, version 2.6. i read some
> > > > manuals, howtos, have already made some really simple modules, but when
> > > > I tried to do a little more complex work, I stumbled across some
> > > > dificulties.
> > > > well, what I want to is a kernel module that opens a regular file,
> > > > writes something to it, and closes it. easy, isn't it? I also thought
> > > > that
> > > >
> > > > but then I tried making a simple open over the file, but the module
> > > > complains it can't find the symbols open, close and write. Is there
> > > Are you doing OPEN(filename, flags)?
> > > > anything unusual I must do to work with files in the kernel? none of
> > > > the manuals I read mentioned how to open and do some I/O over it.
> > > >
> > > > now, to my real problem: I must record some sound, and then play it!
> > > > since in LInux everything is a file, I'm able to do it by means of
> > > > /dev/dsp. that's why I asked abou t how to work with regular files. but
> > > > I don't know if this way of accessing devices hold for modules. and I
> > > > can't open that file!
> > > >
> > > > I looked at /proc/kallsyms, and open is there. I don't have a clue why
> > > > the module complains it couldn't find the open.
> > > Kernel opens the files with sys_open, similary sys_close, sys_read,
> > > sys_write and so on.
> > > >
> > > > thanks for any help you could provide, and sorry for such noob question

thank you. now I understand that I shouldn't read/write files from a
module. even because there's no sense about the kernel dealing with
files, and it's dangerous. well, there's some time I studied operating
systems in college .
and with this, I know I can't use the soudcard as a file(at least this
is not the usual way to do). probably I need to use some kernel
structure?
regards,

ask wrote:
> There is one link in the reference link at this place, just what you
> want:how to read file from kernel:
>
> http://www.rtprogramming.blogspot.com/
>
>
>
>
> Yellow wrote:
> > oh, sorry, but maybe I didn't make myself clear last post: what I'd
> > like to know is how can I use the soundcard in kernel space. if it
> > doesn't involve any operations with device files, please, don't stick
> > to the reading/writing to file issue.
> > regards
> >
> > Yellow wrote:
> > > thanks for all the replies. I tried using sys_open, and "aparently" I
> > > could open the file, but I couldn't write or read it using sys_write or
> > > sys_read. Linux complains it can't find the sys_read and sys_write
> > > symbols.
> > > I also tried using filp_open and filp_open, but got a segmentation
> > > fault .
> > > here's my code, and what I want to do first:
> > >
> > > int init_module(void)
> > > {
> > > int fd;
> > > printk(KERN_ALERT "module loaded\n");
> > > fd = open("/home/alisson/texte.txt", 02);
> > > if(fd ==-1)
> > > printk(KERN_ALERT "error opening file");
> > > /* write something here */
> > > close(fd);
> > > return 0;
> > > }
> > >
> > > but what I'd like to know is: can I use the sound card the same way I
> > > use it in user space programs? like reading and opening a file? my
> > > final goal is record some sound from the microphone for 3 seconds, and
> > > then play it.
> > >
> > > thanks
> > >
> > >
> > > miline wrote:
> > > > Yellow wrote:
> > > >
> > > > > hi there!
> > > > >
> > > > > I have just started studying the linux kernel, version 2.6. i read some
> > > > > manuals, howtos, have already made some really simple modules, but when
> > > > > I tried to do a little more complex work, I stumbled across some
> > > > > dificulties.
> > > > > well, what I want to is a kernel module that opens a regular file,
> > > > > writes something to it, and closes it. easy, isn't it? I also thought
> > > > > that
> > > > >
> > > > > but then I tried making a simple open over the file, but the module
> > > > > complains it can't find the symbols open, close and write. Is there
> > > > Are you doing OPEN(filename, flags)?
> > > > > anything unusual I must do to work with files in the kernel? none of
> > > > > the manuals I read mentioned how to open and do some I/O over it.
> > > > >
> > > > > now, to my real problem: I must record some sound, and then play it!
> > > > > since in LInux everything is a file, I'm able to do it by means of
> > > > > /dev/dsp. that's why I asked abou t how to work with regular files. but
> > > > > I don't know if this way of accessing devices hold for modules. and I
> > > > > can't open that file!
> > > > >
> > > > > I looked at /proc/kallsyms, and open is there. I don't have a clue why
> > > > > the module complains it couldn't find the open.
> > > > Kernel opens the files with sys_open, similary sys_close, sys_read,
> > > > sys_write and so on.
> > > > >
> > > > > thanks for any help you could provide, and sorry for such noob question

Yellow wrote:

>>>> but what I'd like to know is: can I use the sound card the same way I
>>>> use it in user space programs? like reading and opening a file? my
>>>> final goal is record some sound from the microphone for 3 seconds, and
>>>> then play it.

> thank you. now I understand that I shouldn't read/write files from a
> module.

Why do that in the kernel? That sounds like an user level operation.

yes, that's indeed a user level operation. the soundcard thing was just
an abstraction. to the real problem: I need to acquire the signal of an
A/D converter. this operation is analog to acquiring sound from a sound
card. this A/D will be plugged in a sort of device that measures
vibrations from machines that has engine. this device is called
accelerometer. then, I must pass the data to other device. everything
must be real time. probably hard real time. and everything will be done
using an ARM architecture.
I got Rtai (https://www.rtai.org/), which consists of a patch to the
kernel and a library to create real time programs. I compiled it.
They've done quite a good job. I can make some user level programs hard
real time, but they can't make any system call. So it won't work for
me, because I need access to the A/D converter.
If I want to access devices (make system calls), I must make my program
a kernel module. that's what is said in the rtai manuals. this is my
little story

I may also use uclinux, which is just linux without the MMU
implemented. it's not a real time OS, but it's quite fast, because it
won't need any switch of program address space. obviously, it makes
programming a little trickier.
but my doubt with uclinux is if its programming model is user level
programs, instead of kernel module.

sorry for such a long post
regards,


Joe Beanfish wrote:
> Yellow wrote:
>
> >>>> but what I'd like to know is: can I use the sound card the same way I
> >>>> use it in user space programs? like reading and opening a file? my
> >>>> final goal is record some sound from the microphone for 3 seconds, and
> >>>> then play it.
>
> > thank you. now I understand that I shouldn't read/write files from a
> > module.
>
> Why do that in the kernel? That sounds like an user level operation.