devout: support sysfs attributes for (grand*)parent device

pkgs/devout/devout.fnl

@@ -31,13 +31,18 @@
                name value (pairs expected)]
     (and match? (= value (event:attr name)))))
 
+(fn ancestor-attrs-match? [event expected]
+  (accumulate [match? true
+               name value (pairs expected)]
+    (and match? (= value (event:ancestor-attr name)))))
+
 (fn event-matches? [e terms]
   (accumulate [match? true
                name value (pairs terms)]
     (and match?
          (case name
            :attr (attrs-match? e value)
-           :attrs true
+           :attrs (ancestor-attrs-match? e value)
            other (= value (. e.properties name))))))
 
 (fn read-if-exists [pathname]
@@ -48,6 +53,16 @@
          s1)
     nil nil))
 
+(fn event-ancestor-attr [event name]
+  (fn walk-up [sys-path path name]
+    (when path
+      (or (read-if-exists (.. sys-path "/" path "/" name))
+          (walk-up sys-path (dirname path) name))))
+  (walk-up event.sys-path event.path name))
+
+(fn event-attr [event name]
+  (read-if-exists (..  event.sys-path "/" event.path "/" name)))
+
 (fn parse-event [s]
   (let [at (string.find s "@" 1 true)
         (nl nxt) (string.find s "\0" 1 true)
@@ -61,8 +76,8 @@
       :action (string.sub s 1 (- at 1))
       :format format-event
       :matches? event-matches?
-      :attr (fn [self name]
-              (read-if-exists (..  self.sys-path "/" self.path "/" name)))
+      :attr event-attr
+      :ancestor-attr event-ancestor-attr
       }))
 
 (fn find-in-database [db terms]

pkgs/devout/test.fnl

@@ -133,6 +133,29 @@ MINOR=17")
      (expect (not m)))
    ))
 
+(example
+ "I can find a device matching ancestor sysfs attributes"
+ (let [db (database {:sys-path "./fixtures/sys"})
+       path "/devices/pci0000:00/0000:00:14.0/usb1/1-8/1-8:1.1"
+       e (.. "add@" path "\0ACTION=add\n"
+             (with-open [f (io.open (.. "fixtures/sys" path "/uevent"))]
+               (f:read "*a")))]
+   (db:add e)
+   (let [[m & more] (db:find {:devtype "usb_interface"
+                              :driver "uvcvideo"
+                              :attrs {:idVendor "13d3"
+                                      :manufacturer "Azurewave"
+                                      }})]
+     (expect= m.properties.driver "uvcvideo")
+     (expect= m.properties.interface "14/2/0")
+     (expect= more []))
+
+   (let [[m & more] (db:find {:devtype "usb_interface"
+                              :driver "uvcvideo"
+                              :attrs {:idVendor "23d3"
+                                      :manufacturer "Azurewave"
+                                      }})]
+     (expect (not m)))))
 
 ;;; tests for indices