On 1/21/22 14:24, Alexander Stein wrote:

Am Freitag, 21. Januar 2022, 14:14:01 CET schrieb Marek Vasut:

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On 1/21/22 14:12, Alexander Stein wrote:

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Do not deference the NULL pointer if the bridge does not return a bridge state. Assume a fixed format instead.

Fixes: commit b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present") Signed-off-by: Alexander Stein

alexander.stein@ew.tq-group.com

This can happen if a "ti,sn75lvds83", "lvds-encoder" bridge is attached to it. atomic_get_input_bus_fmts is only implemented for the lvds-decoder case.

drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c index 0655582ae8ed..4cfb6c001679 100644 --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c @@ -361,7 +361,11 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,> bridge_state = drm_atomic_get_new_bridge_state(state,

mxsfb->bridge);

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• bus_format = bridge_state->input_bus_cfg.format;
  

• if (!bridge_state)
  

• 	bus_format = MEDIA_BUS_FMT_FIXED;
  

• else
  

• 	bus_format = bridge_state-
  

input_bus_cfg.format;

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• if (bus_format == MEDIA_BUS_FMT_FIXED) {
  

  dev_warn_once(drm->dev, "Bridge does not provide bus

format, assuming

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			      MEDIA_BUS_FMT_RGB888_1X24.

\n"

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Shouldn't this be fixed on the bridge driver side instead ?

Which bridge driver do you use ?

It's drivers/gpu/drm/bridge/lvds-codec.c. I thought naming the compatibles would suffice. I consider a patch for the bridge driver as a separate issue, hence the warning from mxsfb. Although I'm unsure how/what to implement. Similar to the encode case where the bus format is specified in DT?

I'm sorry, I missed the lvds-codec part. Laurent is already on CC.

Anyway, mxsfb should not never dereference the NULL pointer which drm_atomic_get_new_bridge_state is allowed to return.

That line ^ should be in the commit message.