On 5/11/06, Christian Boon <c.boon@xxxxxxxxxxxxxxxxxxxx> wrote:
Hi, i know it is possible with an ioctl to change a value in a kernel module. Is it possible to let a kernel module change a value in user space when some kind of error occurs? so that i dont need to check 'if' an error occured. Christian.
Hi, Checkout the function "call_usermodehelper" in kmod.c. /** * call_usermodehelper - start a usermode application * @path: pathname for the application * @argv: null-terminated argument list * @envp: null-terminated environment list * @wait: wait for the application to finish and return status. * * Runs a user-space application. The application is started * asynchronously if wait is not set, and runs as a child of keventd. * (ie. it runs with full root capabilities). * * Must be called from process context. Returns a negative error code * if program was not execed successfully, or 0. */ int call_usermodehelper(char *path, char **argv, char **envp, int wait) This function can be used to call a user space application from kernel. So kernel won't be actually calling a "call back function" but a "call back application". However, you can write this application to perform whatever you want to do. (This mechanism is actually used to call hot plug agent scripts when a hot-plug event is detected by the kernel). Hope that helps, Rajat -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
