Changes between Initial Version and Version 1 of tty_driver

Timestamp:

Oct 13, 2014, 12:51:08 PM (10 years ago)

Author:

alain

Comment:

--

tty_driver

@@ +1 @@
+= GIET-VM / TTY Driver =
+
+[[PageOutline]]
+
+The [source:soft/giet_vm/giet_drivers/tty_driver.c tty_driver.c] and [source:soft/giet_vm/giet_drivers/tty_driver.h tty_driver.h] files define the TTY driver. 
+
+This ''vci_multi_tty'' component is a multi-terminals controller. It is an ''external'' peripheral.
+
+The total number of terminals must be defined by the configuration  parameter NB_TTY_CHANNELS in the hard_config.h file.
+
+The kernel terminal is TTY[0]. The "user" TTYs are allocated to applications by the GIET in the boot phase, as defined in the mapping_info data structure. The corresponding tty_id must be stored in the context of the task by the boot code.
+
+The SEG_TTY_BASE address must be defined in the hard_config.h file.
+
+The virtual base address of the associated segment is  vbase = SEG_TTY_BASE + cluster_io << 32
+
+The addressable registers map are defined [source:soft/giet_vm/giet_drivers/tty_driver.h here].
+
+
+
+
+
+
+ === unsigned int '''_tty_get_register'''( unsigned int channel,   unsigned int index ) ===
+This low level function returns the value of register (channel / index).
+
+ === void '''_tty_set_register'''( unsigned int channel,  unsigned int index,  unsigned int value ) ===
+This low level function set a new value in register (channel / index).
+
+ === unsigned int '''_tty_write'''( const char*  buffer,  unsigned int length,  unsigned int channel ) ===  
+This non-blocking function writes a character string from a fixed-length buffer to a TTY terminal identified by the channel argument. This function is intended to be used to handle a system call, and should not be used by the kernel for log messages on TTY 0. If channel argument is 0xFFFFFFFF, the TTY index is found in the task context. 
+It is non blocking: it tests the TTY_STATUS register, and stops the transfer as soon as the TTY_STATUS[WRITE] bit is set. 
+Returns  the number of characters that have been written.
+
+ === unsigned int '''_tty_read'''(  char* buffer,  unsigned int length,  unsigned int channel ) === 
+This non-blocking function fetches one character from the terminal identified by the channel argument. If the channel argument is 0xFFFFFFFF, the channel index is obtained from the current task context. 
+It uses the TTY_GET_IRQ[tty_id] interrupt and the buffer must have been filled by the TTY_ISR.
+It test the _tty_rx_full[tty_id] variable, read the _tty_rx_buf[tty_id] buffer, writes this character to the target buffer, and resets the_tty_rx_full[tty_id] register. The length argument is not used.
+Returns  the number of characters that have been read (0/1).
+
+ === void '''_tty_get_lock'''( unsigned int  channel,   unsigned int* save_sr_ptr ) ===
+This blocking function try to take the lock protecting exclusive access to TTY terminal identified by the "channel" argument.
+It enters a critical section before taking the lock, and save the SR value at address defined by the ''save_sr_ptr'' argument.
+It returns only when the lock has been successfully taken.
+
+ === void '''_tty_release_lock'''( unsigned int  channel,  unsigned int* save_sr_ptr ) ===
+This function releases the lock protecting exclusive access to TTY terminal identified by the channel argument.
+It exit the critical section after lock release, and restore SR value from address defined by the ''save_sr_ptr'' argument.
+
+ === void '''_tty_rx_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
+This Interrupt Service Routine handles the IRQ signaling that the RX buffer  is not empty. IT can be an HWI or an SWI.
+There is one communication buffer _tty_rx_buf[i] and one synchronisation variable _tty_rx_full[i] per channel.
+It does nothing if the TTY_RX buffer is empty, or if the kernel buffer is full when the ISR is called.
+
+ === void '''_tty_tx_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
+This Interrupt Service Routine handles the IRQ signaling that the TX buffer is empty. IT can be an HWI or an SWI.
+There is one communication buffer _tty_rx_buf[i] and one synchronisation variable _tty_rx_full[i] per channel.
+A character is lost if the buffer is full when the ISR is executed.
+It is not implemented yet...
+