Changeset 539 for trunk/kernel/devices/dev_txt.h

Timestamp:

Sep 21, 2018, 10:21:42 PM (5 years ago)

Author:

nicolas.van.phan@…

Message:

TTY MUX 4 : Multiplex TTY character sending

Now, when a thread wants to write to a tty,
when the dev_txt_write() or dev_txt_sync_write() are called,
they all call soclib_mtty_aux() with a channel number.
The soclib_mtty_aux() function will write the string char by char,
with each char preceded by the channel number, so that the receiving end
knows to which tty a character is addressed to.

N.B. dev_txt_write() makes *synchronous* writes for the moment
because unlike the vci_tty_tsar, the vci_multi_tty doesn't raise
interrupt except when a new char is received, so we can't use the
interrupt mechanism for writes.

N.B. Now, the TTY DEV threads all write to the same register (WRITE),
but when a thread sends a 2-byte (tty dest. nb. + char), the two must be
send consecutively, without another thread sending a byte in between.
Consequently, a lock has been added to guarantee this atomicity.

File:

• trunk/kernel/devices/dev_txt.h (modified) (1 diff)

trunk/kernel/devices/dev_txt.h

@@ -106 +106 @@
     char      * buffer;    /*! local pointer on characters array                         */
     uint32_t    count;     /*! number of characters in buffer                            */
+    uint32_t    channel;   /*! channel, aka which tty to write to                        */
 }
 txt_sync_args_t;