Re: [PATCH v5 5/6] drm/msm/dpu: fix error handling in dpu_rm_init

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 14/02/2022 22:15, Abhinav Kumar wrote:
> On 1/21/2022 1:06 PM, Dmitry Baryshkov wrote:
> > Using IS_ERR_OR_NULL() together with PTR_ERR() is a typical mistake. If
> > the value is NULL, then the function will return 0 instead of a proper
> > return code. Moreover none of dpu_hw_*_init() functions can return NULL.
> > So, replace all dpu_rm_init()'s IS_ERR_OR_NULL() calls with IS_ERR().
> Can you please give an example of a case where dpu_hw_*_init() can 
> return NULL?
>
> All dpu_hw_*_init() functions are only called if the corresponding
> hw*_counts are valid. So I would like to understand this.
>
> Now, if NULL is treated as a non-error case, should we atleast print
> a message indicating so?

- No dpu_hw_*init() can return NULL

- If at some point any of these functions returns NULL, it will cause a 
premature dpu_rm_init() termination with the success (=0) status, 
leaving parts of RM uninitialized.

Thus I'm replacing IS_ERR_OR_NULL with IS_ERR()

> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 12 ++++++------
> >   1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c 
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > index 96554e962e38..7497538adae1 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > @@ -109,7 +109,7 @@ int dpu_rm_init(struct dpu_rm *rm,
> >               continue;
> >           }
> >           hw = dpu_hw_lm_init(lm->id, mmio, cat);
> > -        if (IS_ERR_OR_NULL(hw)) {
> > +        if (IS_ERR(hw)) {
> >               rc = PTR_ERR(hw);
> >               DPU_ERROR("failed lm object creation: err %d\n", rc);
> >               goto fail;
> > @@ -126,7 +126,7 @@ int dpu_rm_init(struct dpu_rm *rm,
> >               continue;
> >           }
> >           hw = dpu_hw_merge_3d_init(merge_3d->id, mmio, cat);
> > -        if (IS_ERR_OR_NULL(hw)) {
> > +        if (IS_ERR(hw)) {
> >               rc = PTR_ERR(hw);
> >               DPU_ERROR("failed merge_3d object creation: err %d\n",
> >                   rc);
> > @@ -144,7 +144,7 @@ int dpu_rm_init(struct dpu_rm *rm,
> >               continue;
> >           }
> >           hw = dpu_hw_pingpong_init(pp->id, mmio, cat);
> > -        if (IS_ERR_OR_NULL(hw)) {
> > +        if (IS_ERR(hw)) {
> >               rc = PTR_ERR(hw);
> >               DPU_ERROR("failed pingpong object creation: err %d\n",
> >                   rc);
> > @@ -168,7 +168,7 @@ int dpu_rm_init(struct dpu_rm *rm,
> >               continue;
> >           }
> >           hw = dpu_hw_intf_init(intf->id, mmio, cat);
> > -        if (IS_ERR_OR_NULL(hw)) {
> > +        if (IS_ERR(hw)) {
> >               rc = PTR_ERR(hw);
> >               DPU_ERROR("failed intf object creation: err %d\n", rc);
> >               goto fail;
> > @@ -185,7 +185,7 @@ int dpu_rm_init(struct dpu_rm *rm,
> >               continue;
> >           }
> >           hw = dpu_hw_ctl_init(ctl->id, mmio, cat);
> > -        if (IS_ERR_OR_NULL(hw)) {
> > +        if (IS_ERR(hw)) {
> >               rc = PTR_ERR(hw);
> >               DPU_ERROR("failed ctl object creation: err %d\n", rc);
> >               goto fail;
> > @@ -202,7 +202,7 @@ int dpu_rm_init(struct dpu_rm *rm,
> >               continue;
> >           }
> >           hw = dpu_hw_dspp_init(dspp->id, mmio, cat);
> > -        if (IS_ERR_OR_NULL(hw)) {
> > +        if (IS_ERR(hw)) {
> >               rc = PTR_ERR(hw);
> >               DPU_ERROR("failed dspp object creation: err %d\n", rc);
> >               goto fail;


--
With best wishes
Dmitry