linux: Use K_OFF VT KB mode over K_RAW if available.

Submitted by Arthur Taylor on Jan. 6, 2012, 7:21 a.m.

Details

Message ID 1325834497-15781-1-git-send-email-art@ified.ca
State Accepted
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Commit Message

Arthur Taylor Jan. 6, 2012, 7:21 a.m. 
Linux kernels since 2.6.38 (March 2011) have an VT KB mode K_OFF in
which special keys (like Ctrl+C) are not interpreted and input is not
buffered. Use of this mode over K_RAW removes the need for a
xf86ConsoleHandler to drain the VT input buffer, removing the grief it
causes when it goes wrong or is (de)initialized out-of-order. (This
also saves a few needless context switches per key event.)

If K_OFF is not defined or not understood by the kernel, K_RAW and the
previous method is used as a fall-back.

Signed-off-by: Arthur Taylor <art@ified.ca>
---
 hw/xfree86/os-support/linux/lnx_init.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

Patch hide | download patch | download mbox 

diff --git a/hw/xfree86/os-support/linux/lnx_init.c b/hw/xfree86/os-support/linux/lnx_init.c
index 5f3e3a9..699e8c5 100644
--- a/hw/xfree86/os-support/linux/lnx_init.c
+++ b/hw/xfree86/os-support/linux/lnx_init.c
@@ -212,10 +212,20 @@  xf86OpenConsole(void)
             tcgetattr(xf86Info.consoleFd, &tty_attr);
 	    SYSCALL(ioctl(xf86Info.consoleFd, KDGKBMODE, &tty_mode));
 
-	    SYSCALL(ret = ioctl(xf86Info.consoleFd, KDSKBMODE, K_RAW));
+#ifdef K_OFF 
+	    /* disable kernel special keys and buffering */
+	    SYSCALL(ret = ioctl(xf86Info.consoleFd, KDSKBMODE, K_OFF));
 	    if (ret < 0)
-		FatalError("xf86OpenConsole: KDSKBMODE K_RAW failed %s\n",
-			strerror(errno));
+#endif
+	    {
+		SYSCALL(ret = ioctl(xf86Info.consoleFd, KDSKBMODE, K_RAW));
+		if (ret < 0)
+		    FatalError("xf86OpenConsole: KDSKBMODE K_RAW failed %s\n",
+			    strerror(errno));
+
+		/* need to keep the buffer clean, else the kernel gets angry */
+		xf86SetConsoleHandler(drain_console, NULL);
+	    }
 
             nTty = tty_attr;
             nTty.c_iflag = (IGNPAR | IGNBRK) & (~PARMRK) & (~ISTRIP);
@@ -228,9 +238,6 @@  xf86OpenConsole(void)
             cfsetospeed(&nTty, 9600);
             tcsetattr(xf86Info.consoleFd, TCSANOW, &nTty);
 
-            /* need to keep the buffer clean, else the kernel gets angry */
-	    xf86SetConsoleHandler(drain_console, NULL);
-
 	    /* we really should have a InitOSInputDevices() function instead
 	     * of Init?$#*&Device(). So I just place it here */
         }

Comments

Adam Jackson Jan. 6, 2012, 7:21 p.m. 
On 1/6/12 2:21 AM, Arthur Taylor wrote:
> Linux kernels since 2.6.38 (March 2011) have an VT KB mode K_OFF in
> which special keys (like Ctrl+C) are not interpreted and input is not
> buffered. Use of this mode over K_RAW removes the need for a
> xf86ConsoleHandler to drain the VT input buffer, removing the grief it
> causes when it goes wrong or is (de)initialized out-of-order. (This
> also saves a few needless context switches per key event.)
>
> If K_OFF is not defined or not understood by the kernel, K_RAW and the
> previous method is used as a fall-back.
>
> Signed-off-by: Arthur Taylor<art@ified.ca>

Reviewed-by: Adam Jackson <ajax@redhat.com>

Merged in my 1.12 tree.

- ajax