Dear Lazyweb,

I have several Blackmagic MiniRecoder SDI → Thunderbolt dinguses. Every now and then they lose their minds and stop producing video unless unplugged and re-plugged.

Two questions:

1. How can I reset it without physical access? Is there some way to reset the whole thunderbolt bus, or to power-cycle all devices attached to it?

   I have also noticed that sometimes it gets weirdly finicky about the cab.e Sometimes reversing the cable is necessary to make it work again. I have a stack of these fucking cables, some brand new, and sometimes one works and another doesn't; and then they trade, and the old one is the only one that will work.

2. How can I detect the thing having gone into the bad state?

   When it is in the bad state, the "Blackmagic Desktop Video / Desktop Video Setup" app consistently says "No desktop video device connected" rather than listing the device name. So what I want to know is, how do I get that status result from a command line tool?

   When it is in the bad state, "system_profiler SPThunderboltDataType -json" still lists the device. At some point I had believed that if link_status_key was 0x1 or 0x2, things were good, otherwise they were bad, but that is not good enough, apparently, since right now I'm seeing 0x2 but it's not working.

   Here's the output on a Mac mini i5, 10.15.7, with a MiniRecorder in a working state:

   {
     "SPThunderboltDataType" : [
       {
         "_items" : [
           {
             "_name" : "UltraStudio Mini Recorder",
             "device_id_key" : "0xA129",
             "device_name_key" : "UltraStudio Mini Recorder",
             "device_revision_key" : "0x1",
             "receptacle_upstream_ambiguous_tag" : {
               "cm_asn_key" : "C4M050204F5F797AG",
               "cm_version_key" : "1.0.16",
               "current_speed_key" : "Up to 10 Gb/s x1",
               "link_status_key" : "0x2",
               "pm_version_key" : "0.2.5",
               "receptacle_status_key" : "receptacle_connected"
             },
             "route_string_key" : "1",
             "switch_uid_key" : "0x0004000000130970",
             "switch_version_key" : "7.2",
             "vendor_id_key" : "0x4",
             "vendor_name_key" : "Blackmagic Design"
           }
         ],
         "_name" : "thunderbolt_bus",
         "device_name_key" : "Mac mini",
         "domain_uuid_key" : "73874C54-62C9-C753-BD76-E1EA186DD0DD",
         "receptacle_1_tag" : {
           "cm_asn_key" : "C4M050204F5F797AG",
           "cm_version_key" : "1.0.16",
           "current_speed_key" : "Up to 10 Gb/s x1",
           "lc_version_key" : "0.12.3",
           "link_status_key" : "0x2",
           "receptacle_id_key" : "1",
           "receptacle_status_key" : "receptacle_connected"
         },
         "route_string_key" : "0",
         "switch_uid_key" : "0x0001000D194BC520",
         "switch_version_key" : "23.4",
         "vendor_name_key" : "Apple Inc."
       }
     ]
   }

   And here it is on a Mac mini i7, 12.6, with a MiniRecorder in the bad state:

   {
     "SPThunderboltDataType" : [
       {
         "_items" : [
           {
             "_name" : "UltraStudio Mini Recorder",
             "device_id_key" : "0xA129",
             "device_name_key" : "UltraStudio Mini Recorder",
             "device_revision_key" : "0x1",
             "mode_key" : "thunderbolt_one",
             "receptacle_upstream_ambiguous_tag" : {
               "cm_asn_key" : "C4M310400W1F798A5",
               "cm_version_key" : "1.0.16",
               "current_speed_key" : "Up to 10 Gb/s x1",
               "link_status_key" : "0x2",
               "pm_version_key" : "0.2.5",
               "receptacle_status_key" : "receptacle_connected"
             },
             "route_string_key" : "3",
             "switch_uid_key" : "0x00040000001FD690",
             "switch_version_key" : "7.2",
             "vendor_id_key" : "0x4",
             "vendor_name_key" : "Blackmagic Design"
           }
         ],
         "_name" : "thunderbolt_bus",
         "device_name_key" : "Mac mini",
         "domain_uuid_key" : "C6AAD605-5E79-5159-B46F-80B40E12FDBA",
         "receptacle_1_tag" : {
           "current_link_width_key" : "0x1",
           "current_speed_key" : "Up to 20 Gb/s x1",
           "lc_version_key" : "0.14.0",
           "link_status_key" : "0x7",
           "receptacle_id_key" : "1",
           "receptacle_status_key" : "receptacle_no_devices_connected"
         },
         "receptacle_2_tag" : {
           "cm_asn_key" : "C4M310400W1F798A5",
           "cm_version_key" : "1.0.16",
           "current_link_width_key" : "0x1",
           "current_speed_key" : "Up to 10 Gb/s x1",
           "lc_version_key" : "0.14.0",
           "link_status_key" : "0x2",
           "receptacle_id_key" : "2",
           "receptacle_status_key" : "receptacle_connected"
         },
         "route_string_key" : "0",
         "switch_uid_key" : "0x000100150242A160",
         "switch_version_key" : "26.1",
         "vendor_name_key" : "Apple Inc."
       }
     ]
   }

Previously, previously, previously.