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Subject[patch] 2.2.18 serial console sysrq backport
Hi *,

i just backported the 2.4.x serial.c changes to enable MAGIC_SYSRQ via
serial console
on 2.2.18. Patch is working ok so far, i have included it here, maybe it
is useful for
someone. You need to enable CONFIG_SERIAL_CONSOLE && CONFIG_MAGIC_SYSRQ
to use it.
To trigger MAGIC_SYSRQ send a "break" to the serial console. e.g.
ALT-a f in minicom. (To trigger the help function try alt-a f h)

Cheers,
-Michael

--
Sik an regeln ortografi unt gramatik su halten erhohen
ferstandlikkeit von gesribene tekste erheblik.--- linux/drivers/char/serial.c.orig Fri Feb 2 10:13:25 2001
+++ linux/drivers/char/serial.c Fri Feb 2 10:35:39 2001
@@ -143,6 +143,10 @@
#include <linux/console.h>
#endif

+#ifdef CONFIG_MAGIC_SYSRQ
+#include <linux/sysrq.h>
+#endif
+
#include <asm/system.h>
#include <asm/io.h>
#include <asm/irq.h>
@@ -178,6 +182,9 @@
#ifdef CONFIG_SERIAL_CONSOLE
static struct console sercons;
#endif
+#if defined(CONFIG_SERIAL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+static unsigned long break_pressed; /* break, really ... */
+#endif

static unsigned detect_uart_irq (struct serial_state * state);
static void autoconfig(struct serial_state * info);
@@ -376,7 +383,7 @@
}

static _INLINE_ void receive_chars(struct async_struct *info,
- int *status)
+ int *status, struct pt_regs * regs)
{
struct tty_struct *tty = info->tty;
unsigned char ch;
@@ -403,6 +410,21 @@
if (*status & UART_LSR_BI) {
*status &= ~(UART_LSR_FE | UART_LSR_PE);
icount->brk++;
+ /*
+ * We do the SysRQ and SAK checking
+ * here because otherwise the break
+ * may get masked by ignore_status_mask
+ * or read_status_mask.
+ */
+#if defined(CONFIG_SERIAL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+ if (info->line == sercons.index) {
+ if (!break_pressed) {
+ break_pressed = jiffies;
+ goto ignore_char;
+ }
+ break_pressed = 0;
+ }
+#endif
} else if (*status & UART_LSR_PE)
icount->parity++;
else if (*status & UART_LSR_FE)
@@ -447,6 +469,17 @@
}
}
}
+#if defined(CONFIG_SERIAL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+ if (break_pressed && info->line == sercons.index) {
+ if (ch != 0 &&
+ time_before(jiffies, break_pressed + HZ*5)) {
+ handle_sysrq(ch, regs, NULL, NULL);
+ break_pressed = 0;
+ goto ignore_char;
+ }
+ break_pressed = 0;
+ }
+#endif
tty->flip.flag_buf_ptr++;
tty->flip.char_buf_ptr++;
tty->flip.count++;
@@ -612,7 +645,7 @@
printk("status = %x...", status);
#endif
if (status & UART_LSR_DR)
- receive_chars(info, &status);
+ receive_chars(info, &status, regs);
check_modem_status(info);
if (status & UART_LSR_THRE)
transmit_chars(info, 0);
@@ -676,7 +709,7 @@
printk("status = %x...", status);
#endif
if (status & UART_LSR_DR)
- receive_chars(info, &status);
+ receive_chars(info, &status, regs);
check_modem_status(info);
if (status & UART_LSR_THRE)
transmit_chars(info, 0);
@@ -739,7 +772,7 @@
printk("status = %x...", status);
#endif
if (status & UART_LSR_DR)
- receive_chars(info, &status);
+ receive_chars(info, &status, regs);
check_modem_status(info);
if (status & UART_LSR_THRE)
transmit_chars(info, 0);
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