diff mbox

[03/11] fblog: new framebuffer kernel log dummy driver

Message ID 1344783205-2384-4-git-send-email-dh.herrmann@googlemail.com (mailing list archive)
State New, archived
Headers show

Commit Message

David Herrmann Aug. 12, 2012, 2:53 p.m. UTC 
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 it 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@googlemail.com>
---
 drivers/video/Kconfig          |  5 +----
 drivers/video/Makefile         |  2 +-
 drivers/video/console/Kconfig  | 37 +++++++++++++++++++++++++++++--------
 drivers/video/console/Makefile |  1 +
 drivers/video/console/fblog.c  | 41 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 73 insertions(+), 13 deletions(-)
 create mode 100644 drivers/video/console/fblog.c

Comments

Ryan Mallon Aug. 12, 2012, 11:34 p.m. UTC | #1 
On 13/08/12 00:53, David Herrmann wrote:
> 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 it 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@googlemail.com>

Hi David,

Couple of comments below.

~Ryan

>  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

You could just place all of the CONFIG_VT options inside an if VT and
then the new fblog options in the else case rather than modifying all of
the (already overly long) depends statements.

> +config FBLOG
> +	tristate "Framebuffer Kernel Log Driver"
> +	depends on !VT && FB
> +	default n

Default n is not required, all options are default n unless otherwise
specified. I don't think you need the dependency on FB either, since
this file should only get included if CONFIG_FB is set?

> +	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.

Do command line options exist to specify screens to write the debug log
to? It might be a useful feature to have.

~Ryan

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David Herrmann Aug. 14, 2012, 9:42 a.m. UTC | #2 
Hi Ryan

On Mon, Aug 13, 2012 at 1:34 AM, Ryan Mallon <rmallon@gmail.com> wrote:
> >  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
>
> You could just place all of the CONFIG_VT options inside an if VT and
> then the new fblog options in the else case rather than modifying all of
> the (already overly long) depends statements.

Indeed, that sounds better.

> > +config FBLOG
> > +     tristate "Framebuffer Kernel Log Driver"
> > +     depends on !VT && FB
> > +     default n
>
> Default n is not required, all options are default n unless otherwise
> specified. I don't think you need the dependency on FB either, since
> this file should only get included if CONFIG_FB is set?

I will remove the default-line, but the FB-dependency is required. The
"console/" directory includes also drivers like vgacon which do not
depend on FB so it gets always included.

> > +     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.
>
> Do command line options exist to specify screens to write the debug log
> to? It might be a useful feature to have.

See patch-7. However, I am not entirely happy with it. I will probably
have to rethink the parameters.

Thanks for reviewing. I will fix all these in the next series.
Regards
David
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diff mbox

Patch

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 e2c96d0..7374362 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 9a52226..ec0e155 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-$(CONFIG_FBLOG)               += fblog.o font.o fbdraw.o
 obj-$(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..fb39737
--- /dev/null
+++ b/drivers/video/console/fblog.c
@@ -0,0 +1,41 @@ 
+/*
+ * Framebuffer Kernel Log Driver
+ * Copyright (c) 2012 David Herrmann <dh.herrmann@googlemail.com>
+ */
+
+/*
+ * 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.
+ * This driver forcibly writes to the framebuffer while active, therefore, you
+ * cannot run other graphics applications simultaneously. You need to disable
+ * all fblog instances before running other graphics applications.
+ */
+
+#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@googlemail.com>");
+MODULE_DESCRIPTION("Framebuffer Kernel Log Driver");