Handle 3rd-level arguments appropriately

Before, `vcgencmd vcos 0` would inappropriately suggest display numbers.

Author: rgm3

host_applications/linux/apps/gencmd/vcgencmd-completion-test.bats

@@ -40,6 +40,10 @@ complete_command() {
   fi
 }
 
+is_pi4() {
+  grep -qE '^Model.* Raspberry Pi 4' /proc/cpuinfo
+}
+
 @test "vcgencmd - -> -t -h --help" {
   complete_command "vcgencmd -"
   [[ "${COMPREPLY[*]}" == "-t -h --help" ]]
@@ -108,11 +112,31 @@ complete_command() {
   [[ "${COMPREPLY[*]}" == "0 1" ]]
 }
 
+# Pi 4B has two hdmi pixel freq limits 0 and 1, Pi 2 and 3 just have one
 @test "get_config hdmi_pixel_freq_li -> hdmi_pixel_freq_limit:0" {
+  if is_pi4; then
+    skip "test only valid with 1 hdmi (earlier pi models)"
+  fi
   complete_command "vcgencmd get_config hdmi_pixel_freq_li"
   [[ "${COMPREPLY[*]}" == "hdmi_pixel_freq_limit:0" ]]
 }
 
+@test "get_config hdmi_pixel_freq_li -> hdmi_pixel_freq_limit:" {
+  if ! is_pi4; then
+    skip "test requires Pi 4 with 2 hdmi outputs"
+  fi
+  complete_command "vcgencmd get_config hdmi_pixel_freq_li"
+  [[ "${COMPREPLY[*]}" == "hdmi_pixel_freq_limit:0 hdmi_pixel_freq_limit:1" ]]
+}
+
+@test "get_config hdmi_pixel_freq_limit: -> 0 1" {
+  if ! is_pi4; then
+    skip "test requires Pi 4 with 2 hdmi outputs"
+  fi
+  complete_command "vcgencmd get_config hdmi_pixel_freq_limit:"
+  [[ "${COMPREPLY[*]}" == "0 1" ]]
+}
+
 @test "vcos -> version log" {
   complete_command "vcgencmd vcos "
   echo "${COMPREPLY[*]}" | grep -Ewo "(version|log)"
@@ -168,3 +192,8 @@ complete_command() {
   complete_command "vcgencmd -t vcos log "
   [[ "${COMPREPLY[*]}" == "status" ]]
 }
+
+@test "vcos 0 -> (nothing)" {
+  complete_command "vcgencmd vcos 0 "
+  [[ "${#COMPREPLY[@]}" -eq 0 ]]
+}

host_applications/linux/apps/gencmd/vcgencmd-completion.bash

@@ -96,14 +96,20 @@ _vcgencmd() {
     fi
 
     if [[ $args -eq 3 ]]; then
-        case "$prev" in
-            0|1|-1)
-                opts='0 1 2 3 7'
+        case "${words[cword - 2]}" in
+            display_power)
+                case "$prev" in
+                    0|1|-1)
+                        opts='0 1 2 3 7'
+                        ;;
+                esac
                 ;;
-        esac
-        case "$prev" in
-            log)
-                opts='status'
+            vcos)
+                case "$prev" in
+                    log)
+                        opts='status'
+                        ;;
+                esac
                 ;;
         esac
     fi