firmware_class: skip timeout in request_firmware during boot

[Javier Pello]

Hi,

I have prepared a patch that makes request_firmware skip the usual
grace period that it gives firmware images to show up if it determines
that userspace was not notified at all.

The situation is the following: I have a device that requires firmware
to be loaded during initialisation. However, the driver is built into
the kernel, so it tries to initialise before the root filesystem is
mounted. This results in _request_firmware sending an event to userspace
and patiently waiting for the firmware image to appear (which it cannot
do) until the loading_timeout timer kicks in a minute later, ending up
in -ENOENT. The wait is done synchronously, so the whole kernel is
stopped in the meanwhile; this means a useless boot delay of one minute.

The attached patch fixes this by making _request_firmware check whether
the firmware loading event was succesfully sent to userspace, and skip
the timeout if it has not. The patch comes in two parts:

1. The first part changes kobject_uevent_env in lib/kobject_uevent.c
to report a failure if both netlink_broadcast (if applicable) and
call_usermodehelper fail to send the event to userspace. Nothing in
the kernel seems to care about the return value of kobject_uevent_env,
so this should not break anything.

2. The second part changes _request_firmware in
drivers/base/firmware_class.c to actually check the return value of
kobject_uevent and skip the loading_timeout delay if the loading event
was not delivered to userspace at all.

The patches apply cleanly against 2.6.22. Any suggestions or feedback
will be welcome.

Javier


==========
From: Javier Pello <javier.pello at urjc.es>

kobject_uevent: return an error if event was not delivered to userspace

Make kobject_uevent_env return an error to the caller if the event was
not delivered to userspace either via netlink or via uevent_helper.

Signed-off-by: Javier Pello <javier.pello at urjc.es>

---
diff -u linux-2.6.22/lib/kobject_uevent.c linux-2.6.22-p/lib/kobject_uevent.c
--- linux-2.6.22/lib/kobject_uevent.c	2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.22-p/lib/kobject_uevent.c	2007-07-18 20:17:10.000000000 +0200
@@ -196,7 +196,8 @@
 			}
 
 			NETLINK_CB(skb).dst_group = 1;
-			netlink_broadcast(uevent_sock, skb, 0, 1, GFP_KERNEL);
+			retval = netlink_broadcast(uevent_sock, skb, 0, 1,
+						GFP_KERNEL);
 		}
 	}
 #endif
@@ -208,7 +209,15 @@
 		argv [0] = uevent_helper;
 		argv [1] = (char *)subsystem;
 		argv [2] = NULL;
-		call_usermodehelper (argv[0], argv, envp, 0);
+#if defined(CONFIG_NET)
+		if (retval) {
+			retval = call_usermodehelper (argv[0], argv, envp, 0);
+		} else {
+			call_usermodehelper (argv[0], argv, envp, 0);
+		}
+#else
+		retval = call_usermodehelper (argv[0], argv, envp, 0);
+#endif
 	}
 
 exit:

==========
From: Javier Pello <javier.pello at urjc.es>

request_firmware: skip timeout if userspace was not notified

Stop _request_firmware from setting up a timer and waiting for
the firmware image to appear if kobject_uevent returns an error
(meaning userspace was not notified at all).

This prevents useless delays if there is no userspace tool to
provide the firmware image (eg during boot).

Signed-off-by: Javier Pello <javier.pello at urjc.es>

---
diff -u linux-2.6.22/drivers/base/firmware_class.c linux-2.6.22-p/drivers/base/firmware_class.c
--- linux-2.6.22/drivers/base/firmware_class.c	2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.22-p/drivers/base/firmware_class.c	2007-07-18 20:06:53.000000000 +0200
@@ -420,8 +420,12 @@
 			add_timer(&fw_priv->timeout);
 		}
 
-		kobject_uevent(&f_dev->kobj, KOBJ_ADD);
-		wait_for_completion(&fw_priv->completion);
+		retval = kobject_uevent(&f_dev->kobj, KOBJ_ADD);
+		if (retval) {
+			fw_load_abort(fw_priv);
+		} else {
+			wait_for_completion(&fw_priv->completion);
+		}
 		set_bit(FW_STATUS_DONE, &fw_priv->status);
 		del_timer_sync(&fw_priv->timeout);
 	} else
==========