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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).
This commit is contained in:
Linus Torvalds
@@ -0,0 +1,19 @@
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What: /sys/class/tty/console/active
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Date: Nov 2010
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Contact: Kay Sievers <kay.sievers@vrfy.org>
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Description:
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Shows the list of currently configured
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console devices, like 'tty1 ttyS0'.
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The last entry in the file is the active
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device connected to /dev/console.
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The file supports poll() to detect virtual
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console switches.
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What: /sys/class/tty/tty0/active
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Date: Nov 2010
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Contact: Kay Sievers <kay.sievers@vrfy.org>
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Description:
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Shows the currently active virtual console
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device, like 'tty1'.
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The file supports poll() to detect virtual
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console switches.
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@@ -1181,6 +1181,30 @@ Table 1-12: Files in /proc/fs/ext4/<devname>
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mb_groups details of multiblock allocator buddy cache of free blocks
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..............................................................................
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2.0 /proc/consoles
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------------------
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Shows registered system console lines.
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To see which character device lines are currently used for the system console
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/dev/console, you may simply look into the file /proc/consoles:
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> cat /proc/consoles
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tty0 -WU (ECp) 4:7
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ttyS0 -W- (Ep) 4:64
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The columns are:
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device name of the device
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operations R = can do read operations
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W = can do write operations
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U = can do unblank
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flags E = it is enabled
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C = it is prefered console
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B = it is primary boot console
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p = it is used for printk buffer
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b = it is not a TTY but a Braille device
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a = it is safe to use when cpu is offline
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major:minor major and minor number of the device separated by a colon
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------------------------------------------------------------------------------
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Summary
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@@ -14,6 +14,8 @@ riscom8.txt
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- notes on using the RISCom/8 multi-port serial driver.
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rocket.txt
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- info on the Comtrol RocketPort multiport serial driver.
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serial-rs485.txt
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- info about RS485 structures and support in the kernel.
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specialix.txt
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- info on hardware/driver for specialix IO8+ multiport serial card.
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stallion.txt
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@@ -0,0 +1,120 @@
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RS485 SERIAL COMMUNICATIONS
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1. INTRODUCTION
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EIA-485, also known as TIA/EIA-485 or RS-485, is a standard defining the
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electrical characteristics of drivers and receivers for use in balanced
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digital multipoint systems.
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This standard is widely used for communications in industrial automation
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because it can be used effectively over long distances and in electrically
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noisy environments.
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2. HARDWARE-RELATED CONSIDERATIONS
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Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in
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half-duplex mode capable of automatically controlling line direction by
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toggling RTS or DTR signals. That can be used to control external
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half-duplex hardware like an RS485 transceiver or any RS232-connected
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half-duplex devices like some modems.
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For these microcontrollers, the Linux driver should be made capable of
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working in both modes, and proper ioctls (see later) should be made
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available at user-level to allow switching from one mode to the other, and
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vice versa.
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3. DATA STRUCTURES ALREADY AVAILABLE IN THE KERNEL
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The Linux kernel provides the serial_rs485 structure (see [1]) to handle
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RS485 communications. This data structure is used to set and configure RS485
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parameters in the platform data and in ioctls.
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Any driver for devices capable of working both as RS232 and RS485 should
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provide at least the following ioctls:
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- TIOCSRS485 (typically associated with number 0x542F). This ioctl is used
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to enable/disable RS485 mode from user-space
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- TIOCGRS485 (typically associated with number 0x542E). This ioctl is used
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to get RS485 mode from kernel-space (i.e., driver) to user-space.
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In other words, the serial driver should contain a code similar to the next
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one:
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static struct uart_ops atmel_pops = {
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/* ... */
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.ioctl = handle_ioctl,
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};
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static int handle_ioctl(struct uart_port *port,
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unsigned int cmd,
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unsigned long arg)
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{
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struct serial_rs485 rs485conf;
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switch (cmd) {
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case TIOCSRS485:
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if (copy_from_user(&rs485conf,
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(struct serial_rs485 *) arg,
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sizeof(rs485conf)))
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return -EFAULT;
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/* ... */
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break;
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case TIOCGRS485:
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if (copy_to_user((struct serial_rs485 *) arg,
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...,
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sizeof(rs485conf)))
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return -EFAULT;
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/* ... */
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break;
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/* ... */
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}
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}
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4. USAGE FROM USER-LEVEL
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From user-level, RS485 configuration can be get/set using the previous
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ioctls. For instance, to set RS485 you can use the following code:
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#include <linux/serial.h>
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/* Driver-specific ioctls: */
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#define TIOCGRS485 0x542E
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#define TIOCSRS485 0x542F
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/* Open your specific device (e.g., /dev/mydevice): */
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int fd = open ("/dev/mydevice", O_RDWR);
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if (fd < 0) {
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/* Error handling. See errno. */
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}
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struct serial_rs485 rs485conf;
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/* Set RS485 mode: */
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rs485conf.flags |= SER_RS485_ENABLED;
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/* Set rts delay before send, if needed: */
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rs485conf.flags |= SER_RS485_RTS_BEFORE_SEND;
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rs485conf.delay_rts_before_send = ...;
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/* Set rts delay after send, if needed: */
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rs485conf.flags |= SER_RS485_RTS_AFTER_SEND;
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rs485conf.delay_rts_after_send = ...;
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if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) {
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/* Error handling. See errno. */
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}
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/* Use read() and write() syscalls here... */
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/* Close the device when finished: */
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if (close (fd) < 0) {
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/* Error handling. See errno. */
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}
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5. REFERENCES
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[1] include/linux/serial.h
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