3 files changed, 6 insertions, 2 deletions

diff --git a/libsmctrl.c b/libsmctrl.c
index 69b19a1..640001a 100644
--- a/libsmctrl.c
+++ b/libsmctrl.c
@@ -281,6 +281,7 @@ static int read_int_procfile(char* filename, uint64_t* out) {
 }
 
 static uint64_t tpc_mask_per_gpc_per_dev[16][12];
+// Output mask is vtpc-indexed (virtual TPC)
 int libsmctrl_get_gpc_info(uint32_t* num_enabled_gpcs, uint64_t** tpcs_for_gpc, int dev) {
         uint32_t i, j, vtpc_idx = 0;
         uint64_t gpc_mask, num_tpc_per_gpc, max_gpcs, gpc_tpc_mask;
@@ -322,7 +323,7 @@ int libsmctrl_get_gpc_info(uint32_t* num_enabled_gpcs, uint64_t** tpcs_for_gpc,
                                 // Skip disabled TPCs
                                 if ((1 << j) & gpc_tpc_mask)
                                         continue;
-                                *tpc_mask |= (1 << vtpc_idx);
+                                *tpc_mask |= (1ull << vtpc_idx);
                                 vtpc_idx++;
                 }
         }
diff --git a/libsmctrl.h b/libsmctrl.h
index 7be425d..f342afa 100644
--- a/libsmctrl.h
+++ b/libsmctrl.h
@@ -55,6 +55,9 @@ extern int libsmctrl_get_tpc_info(uint32_t* num_tpcs, int dev);
 // Get number of GPCs for devices number `dev`, and a GPC-indexed array
 // containing masks of which TPCs are associated with each GPC.
 // Note that the `nvdebug` module must be loaded to use this function.
+// @param  num_enabled_gpcs Location to store number of GPCs in
+// @param  tpcs_for_gpc     Pointer to store pointer to output buffer at
+// @return 0 on success, error code on error
 extern int libsmctrl_get_gpc_info(uint32_t* num_enabled_gpcs, uint64_t** tpcs_for_gpc, int dev);
 
 #ifdef __cplusplus
diff --git a/libsmctrl_test_gpc_info.c b/libsmctrl_test_gpc_info.c
index 93bfc1e..5ef44b1 100644
--- a/libsmctrl_test_gpc_info.c
+++ b/libsmctrl_test_gpc_info.c
@@ -8,7 +8,7 @@ int main() {
         libsmctrl_get_gpc_info(&num_gpcs, &masks, 1);
         printf("Num GPCs: %d\n", num_gpcs);
         for (int i = 0; i < num_gpcs; i++) {
-                printf("Mask of TPCs associated with GPC %d: %#lx\n", i, masks[i]);
+                printf("Mask of TPCs associated with GPC %d: %#018lx\n", i, masks[i]);
         }
         return 0;
 }