Clarify the PMU snapshot functionality

The PMU snapshot function is an optional function and the SBI implementation may not implement it. It may be useful to distinguish that from other error to allow further clarification to the user. Signed-off-by: Atish Patra <[email protected]>
riscv-non-isa · Nov 27, 2023 · 1637574 · 1637574
1 parent 7bb328b
commit 1637574
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/src/ext-pmu.adoc b/src/ext-pmu.adoc
@@ -529,6 +529,9 @@ then the PMU snapshot shared memory is cleared and disabled.
 
 The `flags` parameter is reserved for future use and must be zero.
 
+This is an optional function and the SBI implementation may choose not to
+implement it.  
+
 [#table_snapshot_shmem_layout]
 .SBI PMU Snapshot shared memory layout
 [cols="5,2,2,5", width=90%, align="center", options="header"]
@@ -567,6 +570,8 @@ The possible error codes returned in `sbiret.error` are shown in
 |===
 | Error code              | Description
 | SBI_SUCCESS             | Shared memory was set or cleared successfully.
+| SBI_ERR_NOT_SUPPORTED	  | The SBI PMU snapshot functionality is not available
+                            in the SBI implementation. 
 | SBI_ERR_INVALID_PARAM   | The `flags` parameter is not zero or the
                            `shmem_phys_lo` parameter is not 4096 bytes aligned.
 | SBI_ERR_INVALID_ADDRESS | The shared memory pointed to by the `shmem_phys_lo`