[PATCH] kdump: introduce "reset_devices" command line option

[Olaf Hering <olaf@aepfle.de>]

upstream commit 7e96287ddc4f42081e18248b6167041c0908004c
Author: Vivek Goyal <vgoyal@in.ibm.com>

    [PATCH] kdump: introduce "reset_devices" command line option
    
    Resetting the devices during driver initialization can be a costly
    operation in terms of time (especially scsi devices).  This option can be
    used by drivers to know that user forcibly wants the devices to be reset
    during initialization.
    
    This option can be useful while kernel is booting in unreliable
    environment.  For ex.  during kdump boot where devices are in unknown
    random state and BIOS execution has been skipped.
    
    Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

---

This change from 2.6.19-rc1 is required for the following kdump patch.

 Documentation/kernel-parameters.txt |    3 +++
 include/linux/init.h                |    1 +
 init/main.c                         |   20 ++++++++++++++++++++
 3 files changed, 24 insertions(+)

--- linux-2.6.18-xen.hg.orig/Documentation/kernel-parameters.txt
+++ linux-2.6.18-xen.hg/Documentation/kernel-parameters.txt
@@ -1392,6 +1392,9 @@ running once the system is up.
 
 	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
 
+	reset_devices	[KNL] Force drivers to reset the underlying device
+			during initialization.
+
 	resume=		[SWSUSP]
 			Specify the partition device for software suspend
 
--- linux-2.6.18-xen.hg.orig/include/linux/init.h
+++ linux-2.6.18-xen.hg/include/linux/init.h
@@ -68,6 +68,7 @@ extern initcall_t __security_initcall_st
 
 /* Defined in init/main.c */
 extern char saved_command_line[];
+extern unsigned int reset_devices;
 
 /* used by init/main.c */
 extern void setup_arch(char **);
--- linux-2.6.18-xen.hg.orig/init/main.c
+++ linux-2.6.18-xen.hg/init/main.c
@@ -128,6 +128,18 @@ static char *ramdisk_execute_command;
 static unsigned int max_cpus = NR_CPUS;
 
 /*
+ * If set, this is an indication to the drivers that reset the underlying
+ * device before going ahead with the initialization otherwise driver might
+ * rely on the BIOS and skip the reset operation.
+ *
+ * This is useful if kernel is booting in an unreliable environment.
+ * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
+ * skipped and devices will be in unknown state.
+ */
+unsigned int reset_devices;
+EXPORT_SYMBOL(reset_devices);
+
+/*
  * Setup routine for controlling SMP activation
  *
  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
@@ -153,6 +165,14 @@ static int __init maxcpus(char *str)
 
 __setup("maxcpus=", maxcpus);
 
+static int __init set_reset_devices(char *str)
+{
+	reset_devices = 1;
+	return 1;
+}
+
+__setup("reset_devices", set_reset_devices);
+
 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
 static const char *panic_later, *panic_param;