linux-kernel - Re: [PATCH] drm/msm/dpu: Fix usage of ERR

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Date:   Sat, 20 Jun 2020 09:27:56 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Zenghui Yu <yuzenghui@...wei.com>
Cc:     linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        wanghaibin.wang@...wei.com
Subject: Re: [PATCH] drm/msm/dpu: Fix usage of ERR_PTR()

On Sat, Jun 20, 2020 at 3:26 AM Zenghui Yu <yuzenghui@...wei.com> wrote:
>
> ping for this obvious fix...

Hi, thanks, but there is already a similar fix in msm-next:

commit aa472721c8dbe1713cf510f56ffbc56ae9e14247
Refs: v5.7-rc5-33-gaa472721c8db
Author:     Chen Tao <chentao107@...wei.com>
AuthorDate: Mon Jun 8 09:48:59 2020 +0800
Commit:     Rob Clark <robdclark@...omium.org>
CommitDate: Thu Jun 11 20:07:21 2020 -0700

    drm/msm/dpu: fix error return code in dpu_encoder_init

    Fix to return negative error code -ENOMEM with the use of
    ERR_PTR from dpu_encoder_init.

    Fixes: 25fdd5933e4c ("drm/msm: Add SDM845 DPU support")
    Signed-off-by: Chen Tao <chentao107@...wei.com>
    Signed-off-by: Rob Clark <robdclark@...omium.org>


BR,
-R

>
> On 2020/5/28 21:08, Zenghui Yu wrote:
> > ERR_PTR() is used in the kernel to encode an usual *negative* errno code
> > into a pointer.  Passing a positive value (ENOMEM) to it will break the
> > following IS_ERR() check.
> >
> > Though memory allocation is unlikely to fail, it's still worth fixing.
> > And grepping shows that this is the only misuse of ERR_PTR() in kernel.
> >
> > Fixes: 25fdd5933e4c ("drm/msm: Add SDM845 DPU support")
> > Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > index a1b79ee2bd9d..a2f6b688a976 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > @@ -2173,7 +2173,7 @@ struct drm_encoder *dpu_encoder_init(struct drm_device *dev,
> >
> >       dpu_enc = devm_kzalloc(dev->dev, sizeof(*dpu_enc), GFP_KERNEL);
> >       if (!dpu_enc)
> > -             return ERR_PTR(ENOMEM);
> > +             return ERR_PTR(-ENOMEM);
> >
> >       rc = drm_encoder_init(dev, &dpu_enc->base, &dpu_encoder_funcs,
> >                       drm_enc_mode, NULL);
> >