Jon, Yes!... I have CONFIG_EARLY_PRINTK=y, and I could see early prints during booting the kernel. Afterwards, printk's also work as expected. Only printf's from user space has problem.
- Siva -----Original Message----- From: Jon Smirl [mailto:[EMAIL PROTECTED] Sent: Thursday, December 27, 2007 8:16 PM To: Siva Prasad Cc: Nicholas Mc Guire; linuxppc-dev@ozlabs.org; [EMAIL PROTECTED] Subject: Re: Device node - How does kernel know about it On 12/27/07, Siva Prasad <[EMAIL PROTECTED]> wrote: > Thank you Jon and Nicholas. > > I already have "console=ttyS0" in the kernel command line. That is not > helping me. Do you have CONFIG_EARLY_PRINTK=y in .config? > > I looked at the major/minor numbers with a good working system and it > looks correct for the nodes created in ramdisk. > > What is the kernel routine that is first called when there is, for > example a read() function call from user program? > I would like to start debugging from there and see if any thing at all > happens when there is a call. Appreciate your help with this question. > > Thanks > Siva > > > -----Original Message----- > From: Nicholas Mc Guire [mailto:[EMAIL PROTECTED] > Sent: Friday, December 28, 2007 12:39 AM > To: Siva Prasad > Cc: linuxppc-dev@ozlabs.org; [EMAIL PROTECTED] > Subject: Re: Device node - How does kernel know about it > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > * Ramdisk is also executing fine, just that prints are not coming out > of > > serial. I can see the execution of various user programs with a printk > > in sys_execve() routine. Ramdisk has all the required files like > > /dev/console, /dev/ttyS0, etc. > > * Looking further into tty driver, I noticed that call to tty_write() > or > > do_tty_write() is not happening at all. So, somewhere the interface > > between kernel and user program is lost. > > * Just to check it out, I tried to write a small kernel module and a > > test program. > > - Attached memtest.c module (not really testing memory there. :-)) > > - Attached testmemtest.c user program, that just open's it and reads > > the information > > - Created a device node using "mknod /dev/memtest c 168 0" > > - When I do "insmod memtest.ko" inside the ramdisk bootup scripts, I > > could see all the printk's on the console > > - When I execute "testmemtest" next in the same script, it does not > > display the printk inside of memtest.c module. This only indicates > that > > read call did not really go to the kernel side. > > - Just to check my program's validity, I checked on a similar machine > > and all the code works fine. > > - "uname -r" also matches with what I built. So, chances of exiting > > from open call because of mismatch is remote. Since userland cannot > > print, I have no idea what exactly is happening there. > > > The kernel will simply look at the major:minor numbers - so maybe you > simply have a wrong major/minor for /dev/ttyS0 ? in that case you will > see nothing but other than that most things will go on working. > > hofrat > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.2.4 (GNU/Linux) > > iD8DBQFHdLY2nU7rXZKfY2oRApFpAKCKfGanKHGuFFJmUFy3aQtjmWNjEACfU7uK > hrfpn2RMn5l23ZqCOXV5rd8= > =GfsF > -----END PGP SIGNATURE----- > -- Jon Smirl [EMAIL PROTECTED] _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
