[SCSI] Add Kconfig option for asynchronous SCSI scanning
Without this patch, the user has to add a kernel command line parameter
to get asynchronous SCSI scanning. Now they can select the default at
compile time and still override it at boot time if they need to.
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 5881464..8442be1 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -216,6 +216,23 @@
there should be no noticeable performance impact as long as you have
logging turned off.
+config SCSI_SCAN_ASYNC
+ bool "Asynchronous SCSI scanning"
+ depends on SCSI
+ help
+ The SCSI subsystem can probe for devices while the rest of the
+ system continues booting, and even probe devices on different
+ busses in parallel, leading to a significant speed-up.
+ If you have built SCSI as modules, enabling this option can
+ be a problem as the devices may not have been found by the
+ time your system expects them to have been. You can load the
+ scsi_wait_scan module to ensure that all scans have completed.
+ If you build your SCSI drivers into the kernel, then everything
+ will work fine if you say Y here.
+
+ You can override this choice by specifying scsi_mod.scan="sync"
+ or "async" on the kernel's command line.
+
menu "SCSI Transports"
depends on SCSI
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index aa1b1e0..d91d268 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -89,7 +89,13 @@
MODULE_PARM_DESC(max_luns,
"last scsi LUN (should be between 1 and 2^32-1)");
-static char scsi_scan_type[6] = "sync";
+#ifdef CONFIG_SCSI_SCAN_ASYNC
+#define SCSI_SCAN_TYPE_DEFAULT "async"
+#else
+#define SCSI_SCAN_TYPE_DEFAULT "sync"
+#endif
+
+static char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT;
module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO);
MODULE_PARM_DESC(scan, "sync, async or none");