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Commit 56b85f32 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6 

* 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6: (36 commits)
  serial: apbuart: Fixup apbuart_console_init()
  TTY: Add tty ioctl to figure device node of the system console.
  tty: add 'active' sysfs attribute to tty0 and console device
  drivers: serial: apbuart: Handle OF failures gracefully
  Serial: Avoid unbalanced IRQ wake disable during resume
  tty: fix typos/errors in tty_driver.h comments
  pch_uart : fix warnings for 64bit compile
  8250: fix uninitialized FIFOs
  ip2: fix compiler warning on ip2main_pci_tbl
  specialix: fix compiler warning on specialix_pci_tbl
  rocket: fix compiler warning on rocket_pci_ids
  8250: add a UPIO_DWAPB32 for 32 bit accesses
  8250: use container_of() instead of casting
  serial: omap-serial: Add support for kernel debugger
  serial: fix pch_uart kconfig & build
  drivers: char: hvc: add arm JTAG DCC console support
  RS485 documentation: add 16C950 UART description
  serial: ifx6x60: fix memory leak
  serial: ifx6x60: free IRQ on error
  Serial: EG20T: add PCH_UART driver
  ...

Fixed up conflicts in drivers/serial/apbuart.c with evil merge that
makes the code look fairly sane (unlike either side).
parents 3e5b08cb 568389c2

Documentation/ABI/testing/sysfs-tty

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+19 −0
Original line number Diff line number Diff line 
What:		/sys/class/tty/console/active

Date:		Nov 2010

Contact:	Kay Sievers <kay.sievers@vrfy.org>

Description:

		 Shows the list of currently configured

		 console devices, like 'tty1 ttyS0'.

		 The last entry in the file is the active

		 device connected to /dev/console.

		 The file supports poll() to detect virtual

		 console switches.



What:		/sys/class/tty/tty0/active

Date:		Nov 2010

Contact:	Kay Sievers <kay.sievers@vrfy.org>

Description:

		 Shows the currently active virtual console

		 device, like 'tty1'.

		 The file supports poll() to detect virtual

		 console switches.

Documentation/filesystems/proc.txt

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@@ -1181,6 +1181,30 @@ Table 1-12: Files in /proc/fs/ext4/<devname> 
 mb_groups       details of multiblock allocator buddy cache of free blocks

..............................................................................



2.0 /proc/consoles

------------------

Shows registered system console lines.



To see which character device lines are currently used for the system console

/dev/console, you may simply look into the file /proc/consoles:



  > cat /proc/consoles

  tty0                 -WU (ECp)       4:7

  ttyS0                -W- (Ep)        4:64



The columns are:



  device               name of the device

  operations           R = can do read operations

                       W = can do write operations

                       U = can do unblank

  flags                E = it is enabled

                       C = it is prefered console

                       B = it is primary boot console

                       p = it is used for printk buffer

                       b = it is not a TTY but a Braille device

                       a = it is safe to use when cpu is offline

  major:minor          major and minor number of the device separated by a colon



------------------------------------------------------------------------------

Summary

Documentation/serial/00-INDEX

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@@ -14,6 +14,8 @@ riscom8.txt 
	- notes on using the RISCom/8 multi-port serial driver.

rocket.txt

	- info on the Comtrol RocketPort multiport serial driver.

serial-rs485.txt

	- info about RS485 structures and support in the kernel.

specialix.txt

	- info on hardware/driver for specialix IO8+ multiport serial card.

stallion.txt

Documentation/serial/serial-rs485.txt

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                        RS485 SERIAL COMMUNICATIONS



1. INTRODUCTION



   EIA-485, also known as TIA/EIA-485 or RS-485, is a standard defining the

   electrical characteristics of drivers and receivers for use in balanced

   digital multipoint systems.

   This standard is widely used for communications in industrial automation

   because it can be used effectively over long distances and in electrically

   noisy environments.



2. HARDWARE-RELATED CONSIDERATIONS



   Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in

   half-duplex mode capable of automatically controlling line direction by

   toggling RTS or DTR signals. That can be used to control external

   half-duplex hardware like an RS485 transceiver or any RS232-connected

   half-duplex devices like some modems.



   For these microcontrollers, the Linux driver should be made capable of

   working in both modes, and proper ioctls (see later) should be made

   available at user-level to allow switching from one mode to the other, and

   vice versa.



3. DATA STRUCTURES ALREADY AVAILABLE IN THE KERNEL



   The Linux kernel provides the serial_rs485 structure (see [1]) to handle

   RS485 communications. This data structure is used to set and configure RS485

   parameters in the platform data and in ioctls.



   Any driver for devices capable of working both as RS232 and RS485 should

   provide at least the following ioctls:



    - TIOCSRS485 (typically associated with number 0x542F). This ioctl is used

      to enable/disable RS485 mode from user-space



    - TIOCGRS485 (typically associated with number 0x542E). This ioctl is used

      to get RS485 mode from kernel-space (i.e., driver) to user-space.



   In other words, the serial driver should contain a code similar to the next

   one:



	static struct uart_ops atmel_pops = {

		/* ... */

		.ioctl		= handle_ioctl,

	};



	static int handle_ioctl(struct uart_port *port,

		unsigned int cmd,

		unsigned long arg)

	{

		struct serial_rs485 rs485conf;



		switch (cmd) {

		case TIOCSRS485:

			if (copy_from_user(&rs485conf,

				(struct serial_rs485 *) arg,

				sizeof(rs485conf)))

					return -EFAULT;



			/* ... */

			break;



		case TIOCGRS485:

			if (copy_to_user((struct serial_rs485 *) arg,

				...,

				sizeof(rs485conf)))

					return -EFAULT;

			/* ... */

			break;



		/* ... */

		}

	}





4. USAGE FROM USER-LEVEL



   From user-level, RS485 configuration can be get/set using the previous

   ioctls. For instance, to set RS485 you can use the following code:



	#include <linux/serial.h>



	/* Driver-specific ioctls: */

	#define TIOCGRS485      0x542E

	#define TIOCSRS485      0x542F



	/* Open your specific device (e.g., /dev/mydevice): */

	int fd = open ("/dev/mydevice", O_RDWR);

	if (fd < 0) {

		/* Error handling. See errno. */

	}



	struct serial_rs485 rs485conf;



	/* Set RS485 mode: */

	rs485conf.flags |= SER_RS485_ENABLED;



	/* Set rts delay before send, if needed: */

	rs485conf.flags |= SER_RS485_RTS_BEFORE_SEND;

	rs485conf.delay_rts_before_send = ...;



	/* Set rts delay after send, if needed: */

	rs485conf.flags |= SER_RS485_RTS_AFTER_SEND;

	rs485conf.delay_rts_after_send = ...;



	if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) {

		/* Error handling. See errno. */

	}



	/* Use read() and write() syscalls here... */



	/* Close the device when finished: */

	if (close (fd) < 0) {

		/* Error handling. See errno. */

	}



5. REFERENCES



 [1]	include/linux/serial.h

arch/alpha/include/asm/ioctls.h

+1 −0
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@@ -92,6 +92,7 @@ 
#define TIOCGSID	0x5429  /* Return the session ID of FD */

#define TIOCGPTN	_IOR('T',0x30, unsigned int) /* Get Pty Number (of pty-mux device) */

#define TIOCSPTLCK	_IOW('T',0x31, int)  /* Lock/unlock Pty */

#define TIOCGDEV	_IOR('T',0x32, unsigned int) /* Get primary device node of /dev/console */

#define TIOCSIG		_IOW('T',0x36, int)  /* Generate signal on Pty slave */



#define TIOCSERCONFIG	0x5453