linux-kernel - Re: [PATCH 14/19] gpu: drm: selftests: test-drm_dp_mst_helper: Place 'struct drm_dp_sideband_msg_req

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Date:   Mon, 9 Nov 2020 16:12:58 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     David Airlie <airlied@...ux.ie>,
        David Francis <David.Francis@....com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 14/19] gpu: drm: selftests: test-drm_dp_mst_helper: Place
 'struct drm_dp_sideband_msg_req_body' onto the heap

On Mon, 09 Nov 2020, Ville Syrjälä wrote:

> On Thu, Nov 05, 2020 at 02:45:12PM +0000, Lee Jones wrote:
> > The stack is too full.
> > 
> > Fixes the following W=1 kernel build warning(s):
> > 
> >  drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c: In function ‘sideband_msg_req_encode_decode’:
> >  drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c:161:1: warning: the frame size of 1176 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> > 
> > Cc: David Airlie <airlied@...ux.ie>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Lyude Paul <lyude@...hat.com>
> > Cc: David Francis <David.Francis@....com>
> > Cc: dri-devel@...ts.freedesktop.org
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  .../drm/selftests/test-drm_dp_mst_helper.c    | 29 ++++++++++++-------
> >  1 file changed, 18 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c b/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> > index 1d696ec001cff..0a539456f6864 100644
> > --- a/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> > +++ b/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> > @@ -120,44 +120,51 @@ sideband_msg_req_equal(const struct drm_dp_sideband_msg_req_body *in,
> >  static bool
> >  sideband_msg_req_encode_decode(struct drm_dp_sideband_msg_req_body *in)
> >  {
> > -	struct drm_dp_sideband_msg_req_body out = {0};
> > +	struct drm_dp_sideband_msg_req_body *out;
> 
> How big is it? And why is it that big?

It's a struct of a union of structs.

And it's all allocated on the stack.  Bad news!

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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