docs: update and clarify plids option

Make it clearer that for FDP the values specified by the plids option
are indices referencing the list of placement identifiers available to
the namespace.

Also note that it now accepts ranges.

Signed-off-by: Vincent Fu <[email protected]>

HOWTO.rst

@@ -2538,12 +2538,17 @@ with the caveat that when used on the command line, they must come after the
 
 .. option:: plids=str, fdp_pli=str : [io_uring_cmd] [xnvme]
 
-        Select which Placement IDs (streams) or Placement ID Indices (FDP) this
-        job is allowed to use for writes. For FDP by default, the job will
-        cycle through all available Placement IDs, so use this to isolate these
-        identifiers to specific jobs. If you want fio to use FDP placement
-        identifiers only at indices 0, 2 and 5 specify ``plids=0,2,5``. For
-        streams this should be a comma-separated list of Stream IDs.
+        Select which Placement ID Indices (FDP) or Placement IDs (streams) this
+        job is allowed to use for writes. This option accepts a comma-separated
+        list of values or ranges (e.g., 1,2-4,5,6-8).
+
+        For FDP by default, the job will cycle through all available Placement
+        IDs, so use this option to be selective. The values specified here are
+        array indices for the list of placement IDs returned by the nvme-cli
+        command ``nvme fdp status``. If you want fio to use FDP placement
+        identifiers only at indices 0, 2 and 5, set ``plids=0,2,5``.
+
+        For streams this should be a list of Stream IDs.
 
 .. option:: dp_scheme=str : [io_uring_cmd] [xnvme]
 

fio.1

@@ -2305,12 +2305,17 @@ The available placement ID (indices) are defined by \fBplids\fR or
 .RE
 .TP
 .BI (io_uring_cmd,xnvme)plids=str, fdp_pli \fR=\fPstr
-Select which Placement IDs (streams) or Placement ID Indicies (FDP) this job is
-allowed to use for writes.  For FDP by default, the job will cycle through all
-available Placement IDs, so use this to isolate these identifiers to specific
-jobs. If you want fio to use placement identifier only at indices 0, 2 and 5
-specify, you would set `plids=0,2,5`. For streams this should be a
-comma-separated list of Stream IDs.
+Select which Placement ID Indices (FDP) or Placement IDs (streams) this job is
+allowed to use for writes. This option accepts a comma-separated list of values
+or ranges (e.g., 1,2-4,5,6-8).
+
+For FDP by default, the job will cycle through all available Placement IDs, so
+use this option to be selective. The values specified here are array indices
+for the list of placement IDs returned by the nvme-cli command `nvme fdp
+status'. If you want fio to use FDP placement identifiers only at indices 0, 2
+and 5, set `plids=0,2,5'.
+
+For streams this should be a list of Stream IDs.
 .TP
 .BI (io_uring_cmd,xnvme)\fR\fBdp_scheme\fP=str
 Defines which placement ID (index) to be selected based on offset(LBA) range.