How to update driver's .conf file?

Question

After write my device node, I changed some status of the module, and I want to save the change to the driver's .conf file. How can I do ?

Answer 1

Hello.
Is far as I understood you want to change the file "/kernel/drv/xxx.conf" to store your driver's new status there.
I think there are no commands that are explicitely made for modifying the driver's .conf file. The only chance you have is to modify the file directly (by doing fopen(), fwrite() etc.).
There are two ways to do it:
1) From the driver itself:
You may use the vn_xxx commands defined in <sys/vnode.h>. These commands provide the the functionality of open(), write() etc. for kernel drivers but they are not documented. You may have problems if your driver wants to change the .conf file in an early state of booting (before the file systems are mounted).
2) Using a helper daemon:
You may write an additional program which runs as seperate process in the background and checks the driver's state every second or every minute. If the state has changed the driver's .conf file is updated. This variant has some advantages:
- You can use the entire C library (fopen(), ...)
- You do not use undocumented commands
- You can create the new .conf file the following way:
fopen("mydriver.new.conf"...)
unlink("mydriver.conf")
rename("mydriver.new.conf","mydriver.conf")
(The advantage doing so is that a system crash while writing to "mydriver.conf" does not result in a bad file!)
I hope this helps.
Martin