Reviewed-by: Lyude Paul <[email protected]>
On Sat, 2026-08-15 at 21:54 +0200, Marek Czernohous wrote:
> From: Marek Czernohous <[email protected]>
>
> nouveau_dp_irq() looks the encoder up and dereferences it in the same
> breath, five lines before testing it:
>
> struct nouveau_encoder *outp = find_encoder(connector,
> DCB_OUTPUT_DP);
> struct nouveau_drm *drm = nouveau_drm(outp->base.base.dev);
> ...
> if (!outp)
> return;
>
> find_encoder() walks the connector's possible encoders and returns
> NULL
> when none of them matches the requested type, so the NULL test is not
> decoration: it is the author saying this can happen. The initialiser
> above it dereferences the same pointer regardless.
>
> The NULL test predates the dereference. commit 773eb04d14a1
> ("drm/nouveau/disp: expose conn event class") turned nouveau_dp_irq()
> into a work callback, and since the drm pointer was no longer passed
> in
> as an argument it was recovered from the encoder in the declaration
> block, which put the dereference above the existing test.
>
> Move the drm lookup below the test. No functional change when outp is
> non-NULL.
>
> Fixes: 773eb04d14a1 ("drm/nouveau/disp: expose conn event class")
> Cc: [email protected]
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Marek Czernohous <[email protected]>
> ---
> drivers/gpu/drm/nouveau/nouveau_dp.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c
> b/drivers/gpu/drm/nouveau/nouveau_dp.c
> index 55691ec44aba..738802358d85 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dp.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
> @@ -486,7 +486,7 @@ nouveau_dp_irq(struct work_struct *work)
> container_of(work, typeof(*nv_connector), irq_work);
> struct drm_connector *connector = &nv_connector->base;
> struct nouveau_encoder *outp = find_encoder(connector,
> DCB_OUTPUT_DP);
> - struct nouveau_drm *drm = nouveau_drm(outp->base.base.dev);
> + struct nouveau_drm *drm;
> struct nv50_mstm *mstm;
> u64 hpd = 0;
> int ret;
> @@ -494,6 +494,8 @@ nouveau_dp_irq(struct work_struct *work)
> if (!outp)
> return;
>
> + drm = nouveau_drm(outp->base.base.dev);
> +
> mstm = outp->dp.mstm;
> NV_DEBUG(drm, "service %s\n", connector->name);
>
