udev: allow removing tags via TAG-="foobar"

This extends the udev parser to support OP_REMOVE (-=) and adds support
for TAG-= to remove previously set tags. We don't fail if the tag didn't
exist.

This is pretty handy if we ship default rules for seat-assignments and
users want to exclude specific devices from that. They can easily add
rules that drop any automatically added "seat" tags again.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

1 files changed, 20 insertions, 1 deletions

diff --git a/src/libudev/libudev-device.c b/src/libudev/libudev-device.c
index f26a4c44b5..d61a2ad8f4 100644
--- a/src/libudev/libudev-device.c
+++ b/src/libudev/libudev-device.c
@@ -1732,9 +1732,14 @@ void udev_device_set_is_initialized(struct udev_device *udev_device)
         udev_device->is_initialized = true;
 }
 
+static bool is_valid_tag(const char *tag)
+{
+        return !strchr(tag, ':') && !strchr(tag, ' ');
+}
+
 int udev_device_add_tag(struct udev_device *udev_device, const char *tag)
 {
-        if (strchr(tag, ':') != NULL || strchr(tag, ' ') != NULL)
+        if (!is_valid_tag(tag))
                 return -EINVAL;
         udev_device->tags_uptodate = false;
         if (udev_list_entry_add(&udev_device->tags_list, tag, NULL) != NULL)
@@ -1742,6 +1747,20 @@ int udev_device_add_tag(struct udev_device *udev_device, const char *tag)
         return -ENOMEM;
 }
 
+void udev_device_remove_tag(struct udev_device *udev_device, const char *tag)
+{
+        struct udev_list_entry *e;
+
+        if (!is_valid_tag(tag))
+                return;
+        e = udev_list_get_entry(&udev_device->tags_list);
+        e = udev_list_entry_get_by_name(e, tag);
+        if (e) {
+                udev_device->tags_uptodate = false;
+                udev_list_entry_delete(e);
+        }
+}
+
 void udev_device_cleanup_tags_list(struct udev_device *udev_device)
 {
         udev_device->tags_uptodate = false;