Add a new low-level device API to Termios that passes the TTY structure
to the low-level device functions. This greatly simplifies the
low-level device drivers since they are no longer forced to derive their
private data from the minor number.
It makes it possible to use the TTY low-level lock in the device driver
low-level functions which is necessary for proper SMP support. For
example to set the attributes it is often necessary to perform a
read-modify-write operation on a control register used also by interrupt
routines.
A compatibility layer is provided to support device drivers using the
old callback functions so it is not necessary to modify existing device
drivers.
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Overview of newlib support (newlib is from CYGNUS)
Each task can have its own libc state including:
open stdio files
strtok
multi precision arithmetic state
etc.
This is implemented by a reentrancy data structure for each task.
When a task is "started" (in RTEMS sense) the reentrancy structure
is allocated. Its address is stored in notepad[NOTEPAD_LAST].
When task is switched to, the value of global variable _impure_ptr
is changed to the value of the new tasks reentrancy structure.
When a task is deleted
atexit() processing (for that task) happens
task's stdio buffers are flushed
When exit(3) is called
calling task's atexit processing done
global libc state atexit processing done
(this will include any atexit routines installed by drivers)
executive is shutdown
causes a context switch back to bsp land
NOTE:
libc extension are installed by bsp_libc_init()
iff we are using clock interrupts.
This hack is necessary to allow the tmtests to avoid
timing the extensions.
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