[PATCH v1] driver core: Add "*" wildcard support to driver_async_probe cmdline param

[Saravana Kannan <saravanak@google.com>]

There's currently no way to use driver_async_probe kernel cmdline param
to enable default async probe for all drivers.  So, add support for "*"
to match with all driver names.  When "*" is used, all other drivers
listed in driver_async_probe are drivers that will NOT match the "*".

For example:
* driver_async_probe=drvA,drvB,drvC
  drvA, drvB and drvC do asynchronous probing.

* driver_async_probe=*
  All drivers do asynchronous probing except those that have set
  PROBE_FORCE_SYNCHRONOUS flag.

* driver_async_probe=*,drvA,drvB,drvC
  All drivers do asynchronous probing except drvA, drvB, drvC and those
  that have set PROBE_FORCE_SYNCHRONOUS flag.

Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Feng Tang <feng.tang@intel.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 ++++-
 drivers/base/dd.c                               | 9 ++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3f1cc5e317ed..c7513d01df82 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1076,7 +1076,10 @@
 			driver later using sysfs.
 
 	driver_async_probe=  [KNL]
-			List of driver names to be probed asynchronously.
+			List of driver names to be probed asynchronously. *
+			matches with all driver names. If * is specified, the
+			rest of the listed driver names are those that will NOT
+			match the *.
 			Format: <driver_name1>,<driver_name2>...
 
 	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 152d3e6bfc06..16bd8957be61 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -60,6 +60,7 @@ static bool initcalls_done;
 /* Save the async probe drivers' name from kernel cmdline */
 #define ASYNC_DRV_NAMES_MAX_LEN	256
 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
+static bool async_probe_default;
 
 /*
  * In some cases, like suspend to RAM or hibernation, It might be reasonable
@@ -796,7 +797,11 @@ static int driver_probe_device(struct device_driver *drv, struct device *dev)
 
 static inline bool cmdline_requested_async_probing(const char *drv_name)
 {
-	return parse_option_str(async_probe_drv_names, drv_name);
+	bool async_drv;
+
+	async_drv = parse_option_str(async_probe_drv_names, drv_name);
+
+	return (async_probe_default != async_drv);
 }
 
 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
@@ -806,6 +811,8 @@ static int __init save_async_options(char *buf)
 		pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
 
 	strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
+	async_probe_default = parse_option_str(async_probe_drv_names, "*");
+
 	return 1;
 }
 __setup("driver_async_probe=", save_async_options);
-- 
2.36.0.464.gb9c8b46e94-goog