We can use extended format when writing /sys/.../uevent files to
generate synthetic uevents, introduced with commit f36776fafbaa
("kobject: support passing in variables for synthetic uevents").Before using this extended format, we need to know if it's supported and kernel version check may not be appropriate in all cases - there are possible differences from upstream kernel in distributions with backports. This patch adds /sys/kernel/uevent_features file which currently lists 'synthargs' string to denote that the kernel is able to recognize the extended synthetic uevent arguments. Userspace can easily check for the feature then. Signed-off-by: Peter Rajnoha <[email protected]> --- kernel/ksysfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 46ba853656f6..d893d7442f61 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -37,6 +37,13 @@ static ssize_t uevent_seqnum_show(struct kobject *kobj, } KERNEL_ATTR_RO(uevent_seqnum); +static ssize_t uevent_features_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "synthargs\n"); +} +KERNEL_ATTR_RO(uevent_features); + #ifdef CONFIG_UEVENT_HELPER /* uevent helper program, used during early boot */ static ssize_t uevent_helper_show(struct kobject *kobj, @@ -213,6 +220,7 @@ EXPORT_SYMBOL_GPL(kernel_kobj); static struct attribute * kernel_attrs[] = { &fscaps_attr.attr, &uevent_seqnum_attr.attr, + &uevent_features_attr.attr, #ifdef CONFIG_UEVENT_HELPER &uevent_helper_attr.attr, #endif -- 2.19.2
