In the event that the topology requests resources that have not been
created by the system (because they are typically not represented in
dpu_mdss_cfg ^1), the resource(s) in global_state (in this case DSC
blocks, until their allocation/assignment is being sanity-checked in
"drm/msm/dpu: Reject topologies for which no DSC blocks are available")
remain NULL but will still be returned out of
dpu_rm_get_assigned_resources, where the caller expects to get an array
containing num_blks valid pointers (but instead gets these NULLs).
To prevent this from happening, where null-pointer dereferences
typically result in a hard-to-debug platform lockup, num_blks shouldn't
increase past NULL blocks and will print an error and break instead.
After all, max_blks represents the static size of the maximum number of
blocks whereas the actual amount varies per platform.
^1: which can happen after a git rebase ended up moving additions to
_dpu_cfg to a different struct which has the same patch context.
Fixes: bb00a452d6f7 ("drm/msm/dpu: Refactor resource manager")
Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
---
Changes since v2:
- Dropped all 7 other patches that were queued for -next;
- Reworded error message to clarify that the requested resource should
have already been allocated, rather than sounding like
dpu_rm_get_assigned_resources is (re)allocating/(re)assigning
resources here;
- This patch is now (implicitly!) based after "drm/msm/dpu: Reject
topologies for which no DSC blocks are available", which should make
it impossible to reach this condition, making it more of a safeguard
in case of future code changes and/or hidden issues: and is more
clearly conveyed in the patch message as well.
v2: https://lore.kernel.org/linux-arm-msm/20221221231943.1961117-5-marijn.suijten@xxxxxxxxxxxxxx/
drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
index 73b3442e7467..7ada957adbbb 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
@@ -660,6 +660,11 @@ int dpu_rm_get_assigned_resources(struct dpu_rm *rm,
blks_size, enc_id);
break;
}
+ if (!hw_blks[i]) {
+ DPU_ERROR("Allocated resource %d unavailable to assign to enc %d\n",
+ type, enc_id);
+ break;
+ }
blks[num_blks++] = hw_blks[i];
}
--
2.39.0
