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Early printk/console for 2.5.12

PATCH New Keith Mannthey 1 participant 1 message May 3, 2002

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Keith Mannthey

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PATCH 1/1 Early printk/console for 2.5.12

Hello Linus,
The following patch provides the ability to add early
consoles (to use with printk calls before console_init) and then have them automatically removed right before the real consoles are added. This is useful if a kernel doesn't boot past console init.

Included in the patch are 3 drivers for i386. Primarily
there is a VGA driver and a serial console driver that both work well with i386. This has been tested on a desktop PC, an SMP machine, and a 16 processor NUMA-Q.

An earlier variation was submitted by Bill Irwin in
November. This is a cleaned up version a few more features.

I would like this to be added to the kernel to make
early debugging (before console_init) easier and a provide a standard early console.

Thanks for your time,
Keith Mannthey

PS. The patch was generated against 2.5.11, but applies cleanly against 2.5.12

arch/i386/Config.help +20 -0
diff -urN linux-2.5.11/arch/i386/Config.help linux-2.5.11.early/arch/i386/Config.help
@@ -940,3 +940,23 @@
 CONFIG_DEBUG_OBSOLETE
   Say Y here if you want to reduce the chances of the tree compiling,
   and are prepared to dig into driver internals to fix compile errors.
+
+Early printk support
+NO_CONFIG_EARLY_CONSOLE
+  If you are not doing early kernel devolopment NONE is what you want.
+  The other will add a early console for you (in i386)
+  This will allow you see printk output before console_init is called.
+  This is handy if you need to debug the kernel before this point.
+ 
+ VGA will give you a VGA console, your screen.
+ SERIAL will give you out put on your serial line.
+
+Location of serial port
+CONFIG_EARLY_CONSOLE_SERIAL_PORT
+  0x3F8 == COMM 1
+  0x3E8 == COMM 2
+
+Baud rate
+CONFIG_EARLY_CONSOLE_SERIAL_BAUD
+  Set the the Baud of your serial console.
+
arch/i386/config.in +10 -0
diff -urN linux-2.5.11/arch/i386/config.in linux-2.5.11.early/arch/i386/config.in
@@ -408,6 +408,16 @@
    if [ "$CONFIG_HIGHMEM" = "y" ]; then
       bool '  Highmem debugging' CONFIG_DEBUG_HIGHMEM
    fi
+   choice 'Early printk support'  \
+               "NONE               NO_CONFIG_EARLY_CONSOLE \
+                VGA                CONFIG_EARLY_CONSOLE_VGA \
+                Serial_PORT       CONFIG_EARLY_CONSOLE_SERIAL\
+                Bochs_0xE9_hack    CONFIG_EARLY_CONSOLE_BOCHS_E9_HACK " NONE
+   if [ "$CONFIG_EARLY_CONSOLE_SERIAL" = "y" ]; then
+      hex "Location of serial port " CONFIG_EARLY_CONSOLE_SERIAL_PORT 0x3F8
+      int "Baud rate " CONFIG_EARLY_CONSOLE_SERIAL_BAUD  38400
+   fi
+
 fi
 
 endmenu
arch/i386/kernel/Makefile +1 -1
diff -urN linux-2.5.11/arch/i386/kernel/Makefile linux-2.5.11.early/arch/i386/kernel/Makefile
@@ -19,7 +19,7 @@
 obj-y	:= process.o semaphore.o signal.o entry.o traps.o irq.o vm86.o \
 		ptrace.o i8259.o ioport.o ldt.o setup.o time.o sys_i386.o \
 		pci-dma.o i386_ksyms.o i387.o bluesmoke.o dmi_scan.o \
-		bootflag.o
+		bootflag.o early_consoles.o
 
 
 ifdef CONFIG_PCI
arch/i386/kernel/early_consoles.c +417 -0

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arch/i386/kernel/setup.c +3 -1
diff -urN linux-2.5.11/arch/i386/kernel/setup.c linux-2.5.11.early/arch/i386/kernel/setup.c
@@ -672,7 +672,9 @@
 	unsigned long bootmap_size, low_mem_size;
 	unsigned long start_pfn, max_low_pfn;
 	int i;
-
+	
+	add_early_consoles();
+	
 #ifdef CONFIG_VISWS
 	visws_get_board_type_and_rev();
 #endif
drivers/char/console.c +7 -2
diff -urN linux-2.5.11/drivers/char/console.c linux-2.5.11.early/drivers/char/console.c
@@ -2437,7 +2437,8 @@
 {
 	const char *display_desc = NULL;
 	unsigned int currcons = 0;
-
+	int removed =0;
+	
 	if (conswitchp)
 		display_desc = conswitchp->con_startup();
 	if (!display_desc) {

@@ -2513,10 +2514,14 @@
 		display_desc, video_num_columns, video_num_lines);
 	printable = 1;
 	printk("\n");
-
+	
+	/*clear any early consoles*/
+	removed = clear_early_consoles();
+	
 #ifdef CONFIG_VT_CONSOLE
 	register_console(&vt_console_driver);
 #endif
+	printk ("removed %d early consoles \n",removed);
 }
 
 #ifndef VT_SINGLE_DRIVER
include/linux/console.h +5 -1
diff -urN linux-2.5.11/include/linux/console.h linux-2.5.11.early/include/linux/console.h
@@ -90,7 +90,7 @@
 #define CON_PRINTBUFFER	(1)
 #define CON_CONSDEV	(2) /* Last on the command line */
 #define CON_ENABLED	(4)
-
+#define EARLY_CONSOLE   (8) /* Early flag. Remove in con_init  */
 struct console
 {
 	char	name[8];

@@ -105,6 +105,7 @@
 	struct	 console *next;
 };
 
+
 extern void register_console(struct console *);
 extern int unregister_console(struct console *);
 extern struct console *console_drivers;

@@ -112,6 +113,9 @@
 extern void release_console_sem(void);
 extern void console_conditional_schedule(void);
 extern void console_unblank(void);
+extern int clear_early_consoles(void);
+extern void register_early_console(struct console *);
+
 
 /* VESA Blanking Levels */
 #define VESA_NO_BLANKING        0
kernel/printk.c +44 -0

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