Hi Dave And Sandeep, Hope I can contribute and sorry for the interruption of conversation :-(.
On Tue, Jan 10, 2012 at 2:59 PM, Dave Hylands <[email protected]> wrote: > Hi sandeep, > > On Mon, Jan 9, 2012 at 10:37 PM, sandeep kumar > <[email protected]> wrote: > > Hi All, > > > > I want to know "What is a console? > > A console is where the output from printk goes. > > > and Why it is always associated with > > UART?" > Yes, console is output and UART is the hardware device input port.....it can be implemented hardware wise by many different devices, but all of them will speak the UART protocol: http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter and the hardware devices' source codes are in drivers/tty/serial/8250_xxxxx.c for examples (xxxx for different devices). > > While console's may often be associated with a UART (typical for > embedded systems) there is no need or requirement for them to be > associated with a console. You can regitser a console to send the > output wherever you like. > > > What is a serial console?? > > A serial console is a console driver (registered via register_console) > which sends the output to a serial port, typically also allowing the > serial port to be used as a tty interface. > > > Can there be a USB console?? > > Sure. I don't know if a driver for this exists yet, but if it doesn't > you can always write one. > > According to the diagram of the book "Essential Linux Device Drivers" page 175, both the output of serial_core.c and usb-serial.c (which implements the serial signals coming in from the USB interface) are directed to n_tty.c (which essentially goes to the serial console output). So answer is NO, current architecture has the tty console linked to both UART and USB-Serial interface. (a FTDI software driver drivers/usb/serial/ftdi_sio.c is needed to convert the USB signal back to the serial packets structure). > There is already something called a netconsole (see > Documentation/networking/netconsole.txt). This is an example of a > console which isn't associated with a serial port. > > There is also a framebuffer console (See Documentation/fb/fbcon.txt) > > -- > Dave Hylands > Shuswap, BC, Canada > http://www.davehylands.com > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > Happy Hacking..... -- Regards, Peter Teoh
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