[PATCH 01/10] fblog: new framebuffer kernel log dummy driver
From: David Herrmann
Date: Sat Jun 16 2012 - 18:06:48 EST
Fblog displays all kernel log messages on all connected framebuffers. It
replaces fbcon when CONFIG_VT=n is selected. Its main purpose is to debug
boot problems by displaying the whole boot log on the screen. This patch
provides the first dummy module-init/deinit functions.
As is uses all the font and fb functions I placed it in
drivers/video/console. However, this means that we need to move the check
for CONFIG_VT in Makefile/Kconfig from drivers/video into
drivers/video/console as fblog does not depend on CONFIG_VT.
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
---
drivers/video/Kconfig | 5 +---
drivers/video/Makefile | 2 +-
drivers/video/console/Kconfig | 37 +++++++++++++++++++++------
drivers/video/console/Makefile | 1 +
drivers/video/console/fblog.c | 55 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 87 insertions(+), 13 deletions(-)
create mode 100644 drivers/video/console/fblog.c
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 0217f74..e8fd53d 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -2448,10 +2448,7 @@ source "drivers/video/omap/Kconfig"
source "drivers/video/omap2/Kconfig"
source "drivers/video/exynos/Kconfig"
source "drivers/video/backlight/Kconfig"
-
-if VT
- source "drivers/video/console/Kconfig"
-endif
+source "drivers/video/console/Kconfig"
if FB || SGI_NEWPORT_CONSOLE
source "drivers/video/logo/Kconfig"
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index ee8dafb..9f8a7f0 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -11,7 +11,7 @@ fb-y := fbmem.o fbmon.o fbcmap.o fbsysfs.o \
modedb.o fbcvt.o
fb-objs := $(fb-y)
-obj-$(CONFIG_VT) += console/
+obj-y += console/
obj-$(CONFIG_LOGO) += logo/
obj-y += backlight/
diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index c2d11fe..cfee482 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -6,7 +6,7 @@ menu "Console display driver support"
config VGA_CONSOLE
bool "VGA text console" if EXPERT || !X86
- depends on !4xx && !8xx && !SPARC && !M68K && !PARISC && !FRV && !SUPERH && !BLACKFIN && !AVR32 && !MN10300 && (!ARM || ARCH_FOOTBRIDGE || ARCH_INTEGRATOR || ARCH_NETWINDER)
+ depends on VT && !4xx && !8xx && !SPARC && !M68K && !PARISC && !FRV && !SUPERH && !BLACKFIN && !AVR32 && !MN10300 && (!ARM || ARCH_FOOTBRIDGE || ARCH_INTEGRATOR || ARCH_NETWINDER)
default y
help
Saying Y here will allow you to use Linux in text mode through a
@@ -45,7 +45,7 @@ config VGACON_SOFT_SCROLLBACK_SIZE
screenfuls of scrollback buffer
config MDA_CONSOLE
- depends on !M68K && !PARISC && ISA
+ depends on VT && !M68K && !PARISC && ISA
tristate "MDA text console (dual-headed) (EXPERIMENTAL)"
---help---
Say Y here if you have an old MDA or monochrome Hercules graphics
@@ -61,14 +61,14 @@ config MDA_CONSOLE
config SGI_NEWPORT_CONSOLE
tristate "SGI Newport Console support"
- depends on SGI_IP22
+ depends on VT && SGI_IP22
help
Say Y here if you want the console on the Newport aka XL graphics
card of your Indy. Most people say Y here.
config DUMMY_CONSOLE
bool
- depends on VGA_CONSOLE!=y || SGI_NEWPORT_CONSOLE!=y
+ depends on VT && (VGA_CONSOLE!=y || SGI_NEWPORT_CONSOLE!=y)
default y
config DUMMY_CONSOLE_COLUMNS
@@ -89,7 +89,7 @@ config DUMMY_CONSOLE_ROWS
config FRAMEBUFFER_CONSOLE
tristate "Framebuffer Console support"
- depends on FB
+ depends on VT && FB
select CRC32
help
Low-level framebuffer-based console driver.
@@ -122,16 +122,37 @@ config FRAMEBUFFER_CONSOLE_ROTATION
config STI_CONSOLE
bool "STI text console"
- depends on PARISC
+ depends on VT && PARISC
default y
help
The STI console is the builtin display/keyboard on HP-PARISC
machines. Say Y here to build support for it into your kernel.
The alternative is to use your primary serial port as a console.
+config FBLOG
+ tristate "Framebuffer Kernel Log Driver"
+ depends on !VT && FB
+ default n
+ help
+ This driver displays all kernel log messages on all connected
+ framebuffers. It is mutually exclusive with CONFIG_FRAMEBUFFER_CONSOLE
+ and CONFIG_VT. It was mainly created for debugging purposes when
+ CONFIG_VT is not selected but you still want kernel boot messages on
+ the screen.
+
+ This driver overwrites all other graphics output on the framebuffer as
+ long as it is active so the kernel log will always be visible. You
+ need to disable this driver via sysfs to be able to start another
+ graphics application.
+
+ If unsure, say N.
+
+ To compile this driver as a module, choose M here: the module will
+ be called fblog.
+
config FONTS
bool "Select compiled-in fonts"
- depends on FRAMEBUFFER_CONSOLE || STI_CONSOLE
+ depends on FRAMEBUFFER_CONSOLE || STI_CONSOLE || FBLOG
help
Say Y here if you would like to use fonts other than the default
your frame buffer console usually use.
@@ -158,7 +179,7 @@ config FONT_8x8
config FONT_8x16
bool "VGA 8x16 font" if FONTS
- depends on FRAMEBUFFER_CONSOLE || SGI_NEWPORT_CONSOLE || STI_CONSOLE || USB_SISUSBVGA_CON
+ depends on FRAMEBUFFER_CONSOLE || SGI_NEWPORT_CONSOLE || STI_CONSOLE || USB_SISUSBVGA_CON || FBLOG
default y if !SPARC && !FONTS
help
This is the "high resolution" font for the VGA frame buffer (the one
diff --git a/drivers/video/console/Makefile b/drivers/video/console/Makefile
index a862e91..f608c97 100644
--- a/drivers/video/console/Makefile
+++ b/drivers/video/console/Makefile
@@ -20,6 +20,7 @@ font-objs += $(font-objs-y)
# Each configuration option enables a list of files.
+obj-$(CONFIG_FBLOG) += fblog.o font.o
obj-$(CONFIG_DUMMY_CONSOLE) += dummycon.o
obj-$(CONFIG_SGI_NEWPORT_CONSOLE) += newport_con.o font.o
obj-$(CONFIG_STI_CONSOLE) += sticon.o sticore.o font.o
diff --git a/drivers/video/console/fblog.c b/drivers/video/console/fblog.c
new file mode 100644
index 0000000..ea83643
--- /dev/null
+++ b/drivers/video/console/fblog.c
@@ -0,0 +1,55 @@
+/*
+ * Framebuffer Kernel Log Driver
+ * Copyright (c) 2012 David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+/*
+ * Framebuffer Kernel Log
+ * This driver prints the kernel log to all connected display devices. It
+ * replaces CONFIG_VT and cannot run simultaneously with it. It does not provide
+ * any virtual-terminal, though. It should only be used to get kernel boot
+ * messages to debug kernel errors.
+ * Hence, this driver is neither optimized for speed, nor does it provide any
+ * fancy features like colored text output. After booting is done, the init
+ * process should set /sys/class/graphics/fblog/active to 0 which disables this
+ * driver and you can start using the graphics devices. During shutdown, you can
+ * set this to 1 to get log messages again.
+ * This driver forcibly writes to the framebuffer while active, therefore, you
+ * cannot run other graphics applications simultaneously.
+ *
+ * fblog_redraw_line() is heavily based on the fbcon driver. See bitblit.c for
+ * the original implementation copyrighted by:
+ * Copyright (C) 2004 Antonino Daplas <adaplas@xxxxxxx>
+ *
+ * Please note that nearly all functions here must be called with console_lock
+ * held. This way, we have no locking problems and do not need special
+ * synchronization.
+ */
+
+#include <linux/atomic.h>
+#include <linux/console.h>
+#include <linux/fb.h>
+#include <linux/font.h>
+#include <linux/module.h>
+
+static int __init fblog_init(void)
+{
+ return 0;
+}
+
+static void __exit fblog_exit(void)
+{
+}
+
+module_init(fblog_init);
+module_exit(fblog_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Framebuffer Kernel Log Driver");
--
1.7.10.4
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