[pbs-devel] [PATCH proxmox-backup] tape: library status: don't fail if the library does not support DVCID

[Dominik Csapak <d.csapak@proxmox.com>]

some libraries (e.g. Qualstar) don't support the DVCID bit in the READ
ELEMENT (B8) command (to return vendor/model of connected drives), so
make that part optional if it fails. We only ever use the serial number
in the `pmtx` tool, so there is not much downside to not having this.

This increases compatibility with such libraries

Reported in the forum:
https://forum.proxmox.com/threads/cant-query-tape-robot-status.131833/

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 pbs-tape/src/sg_pt_changer.rs | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/pbs-tape/src/sg_pt_changer.rs b/pbs-tape/src/sg_pt_changer.rs
index c5a0b561..6cb3a044 100644
--- a/pbs-tape/src/sg_pt_changer.rs
+++ b/pbs-tape/src/sg_pt_changer.rs
@@ -398,20 +398,22 @@ pub fn read_element_status<F: AsRawFd>(file: &mut F) -> Result<MtxStatus, Error>
 
     // get the serial + vendor + model,
     // some changer require this to be an extra scsi command
-    let page = get_element(
+    // some changers don't support this
+    if let Ok(page) = get_element(
         &mut sg_raw,
         ElementType::DataTransferWithDVCID,
         allocation_len,
         false,
-    )?;
-    // should be in same order and same count, but be on the safe side.
-    // there should not be too many drives normally
-    for drive in drives.iter_mut() {
-        for drive2 in &page.drives {
-            if drive2.element_address == drive.element_address {
-                drive.vendor = drive2.vendor.clone();
-                drive.model = drive2.model.clone();
-                drive.drive_serial_number = drive2.drive_serial_number.clone();
+    ) {
+        // should be in same order and same count, but be on the safe side.
+        // there should not be too many drives normally
+        for drive in drives.iter_mut() {
+            for drive2 in &page.drives {
+                if drive2.element_address == drive.element_address {
+                    drive.vendor = drive2.vendor.clone();
+                    drive.model = drive2.model.clone();
+                    drive.drive_serial_number = drive2.drive_serial_number.clone();
+                }
             }
         }
     }
-- 
2.30.2