Re: accessing files, devices, in kernel modules

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

.

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