[PATCH][next] drm/komeda: remove redundant assignment to pointer disable_done

[PATCH][next] drm/komeda: remove redundant assignment to pointer disable_done

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

The pointer disable_done is being initialized with a value that
is never read and is being re-assigned a little later on. The
assignment is redundant and hence can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
index 75263d8cd0bd..9beeda04818b 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
@@ -296,7 +296,7 @@ komeda_crtc_atomic_disable(struct drm_crtc *crtc,
 	struct komeda_crtc_state *old_st = to_kcrtc_st(old);
 	struct komeda_pipeline *master = kcrtc->master;
 	struct komeda_pipeline *slave  = kcrtc->slave;
-	struct completion *disable_done = &crtc->state->commit->flip_done;
+	struct completion *disable_done;
 	bool needs_phase2 = false;
 
 	DRM_DEBUG_ATOMIC("CRTC%d_DISABLE: active_pipes: 0x%x, affected: 0x%x\n",
-- 
2.20.1

Re: [PATCH][next] drm/komeda: remove redundant assignment to pointer disable_done

[Liviu Dudau]

On Fri, Oct 04, 2019 at 05:21:56PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The pointer disable_done is being initialized with a value that
> is never read and is being re-assigned a little later on. The
> assignment is redundant and hence can be removed.

Not really true, isn't it? The re-assignment is done under the condition that
crtc->state->active is true. disable_done will be used regardless after the if
block, so we can't skip this initialisation.

Not sure why Coverity flags this, but I would NAK this patch.

Best regards,
Liviu

> 
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> index 75263d8cd0bd..9beeda04818b 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> @@ -296,7 +296,7 @@ komeda_crtc_atomic_disable(struct drm_crtc *crtc,
>  	struct komeda_crtc_state *old_st = to_kcrtc_st(old);
>  	struct komeda_pipeline *master = kcrtc->master;
>  	struct komeda_pipeline *slave  = kcrtc->slave;
> -	struct completion *disable_done = &crtc->state->commit->flip_done;
> +	struct completion *disable_done;
>  	bool needs_phase2 = false;
>  
>  	DRM_DEBUG_ATOMIC("CRTC%d_DISABLE: active_pipes: 0x%x, affected: 0x%x\n",
> -- 
> 2.20.1
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

Re: [PATCH][next] drm/komeda: remove redundant assignment to pointer disable_done

[Colin Ian King]

On 04/10/2019 20:27, Liviu Dudau wrote:
> On Fri, Oct 04, 2019 at 05:21:56PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> The pointer disable_done is being initialized with a value that
>> is never read and is being re-assigned a little later on. The
>> assignment is redundant and hence can be removed.
> 
> Not really true, isn't it? The re-assignment is done under the condition that
> crtc->state->active is true. disable_done will be used regardless after the if
> block, so we can't skip this initialisation.
> 
> Not sure why Coverity flags this, but I would NAK this patch.

I'm patching against the driver from linux-next so I believe this is OK
for that. I believe your statement is true against linux which does not
have commit:

d6cb013579e743bc7bc5590ca35a1943f2b8f3c8
Author: Lowry Li (Arm Technology China) <Lowry.Li@arm.com>
Date:   Fri Sep 6 07:18:06 2019 +0000

Colin.

> 
> Best regards,
> Liviu
> 
>>
>> Addresses-Coverity: ("Unused value")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
>> index 75263d8cd0bd..9beeda04818b 100644
>> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
>> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
>> @@ -296,7 +296,7 @@ komeda_crtc_atomic_disable(struct drm_crtc *crtc,
>>  	struct komeda_crtc_state *old_st = to_kcrtc_st(old);
>>  	struct komeda_pipeline *master = kcrtc->master;
>>  	struct komeda_pipeline *slave  = kcrtc->slave;
>> -	struct completion *disable_done = &crtc->state->commit->flip_done;
>> +	struct completion *disable_done;
>>  	bool needs_phase2 = false;
>>  
>>  	DRM_DEBUG_ATOMIC("CRTC%d_DISABLE: active_pipes: 0x%x, affected: 0x%x\n",
>> -- 
>> 2.20.1
>>
> 

Re: [PATCH][next] drm/komeda: remove redundant assignment to pointer disable_done

[Dan Carpenter]

On Fri, Oct 04, 2019 at 10:53:44PM +0100, Colin Ian King wrote:
> On 04/10/2019 20:27, Liviu Dudau wrote:
> > On Fri, Oct 04, 2019 at 05:21:56PM +0100, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> The pointer disable_done is being initialized with a value that
> >> is never read and is being re-assigned a little later on. The
> >> assignment is redundant and hence can be removed.
> > 
> > Not really true, isn't it? The re-assignment is done under the condition that
> > crtc->state->active is true. disable_done will be used regardless after the if
> > block, so we can't skip this initialisation.
> > 
> > Not sure why Coverity flags this, but I would NAK this patch.
> 
> I'm patching against the driver from linux-next so I believe this is OK
> for that. I believe your statement is true against linux which does not
> have commit:
> 
> d6cb013579e743bc7bc5590ca35a1943f2b8f3c8
> Author: Lowry Li (Arm Technology China) <Lowry.Li@arm.com>
> Date:   Fri Sep 6 07:18:06 2019 +0000
> 

It really does help reviewing patches when this is mentioned in the
commit message.

There is some debate about whether this should be mentioned as a Fixes
since it doesn't fix a bug.  I initialy felt it shouldn't be, but now
I think enough people think it should be listed as Fixes that I must be
wrong.  Either way, it's very useful information.

The other thing is that soon get_maintainer.pl will start CC'ing people
from the Fixes tag and right now Lowry Li is not CC'd so that's
unfortunate.

regards,
dan carpenter

Re: [PATCH][next] drm/komeda: remove redundant assignment to pointer disable_done

[james qian wang (Arm Technology China)]

On Mon, Oct 07, 2019 at 04:25:05PM +0300, Dan Carpenter wrote:
> On Fri, Oct 04, 2019 at 10:53:44PM +0100, Colin Ian King wrote:
> > On 04/10/2019 20:27, Liviu Dudau wrote:
> > > On Fri, Oct 04, 2019 at 05:21:56PM +0100, Colin King wrote:
> > >> From: Colin Ian King <colin.king@canonical.com>
> > >>
> > >> The pointer disable_done is being initialized with a value that
> > >> is never read and is being re-assigned a little later on. The
> > >> assignment is redundant and hence can be removed.
> > > 
> > > Not really true, isn't it? The re-assignment is done under the condition that
> > > crtc->state->active is true. disable_done will be used regardless after the if
> > > block, so we can't skip this initialisation.
> > > 
> > > Not sure why Coverity flags this, but I would NAK this patch.
> > 
> > I'm patching against the driver from linux-next so I believe this is OK
> > for that. I believe your statement is true against linux which does not
> > have commit:
> > 
> > d6cb013579e743bc7bc5590ca35a1943f2b8f3c8
> > Author: Lowry Li (Arm Technology China) <Lowry.Li@arm.com>
> > Date:   Fri Sep 6 07:18:06 2019 +0000
> > 
> 
> It really does help reviewing patches when this is mentioned in the
> commit message.
> 
> There is some debate about whether this should be mentioned as a Fixes
> since it doesn't fix a bug.  I initialy felt it shouldn't be, but now
> I think enough people think it should be listed as Fixes that I must be
> wrong.  Either way, it's very useful information.
> 
> The other thing is that soon get_maintainer.pl will start CC'ing people
> from the Fixes tag and right now Lowry Li is not CC'd so that's
> unfortunate.
> 
> regards,
> dan carpenter

Hi Liviu:

Colin's code is right.

Following code I copied from linux-next, and I checked drm-misc, the
code are same. 

        struct komeda_pipeline *slave  = kcrtc->slave;
//---- First initialization.
        struct completion *disable_done = &crtc->state->commit->flip_done;
        bool needs_phase2 = false;

        DRM_DEBUG_ATOMIC("CRTC%d_DISABLE: active_pipes: 0x%x, affected: 0x%x\n",
                         drm_crtc_index(crtc),
                         old_st->active_pipes, old_st->affected_pipes);

        if (slave && has_bit(slave->id, old_st->active_pipes))
                komeda_pipeline_disable(slave, old->state);

        if (has_bit(master->id, old_st->active_pipes))
                needs_phase2 = komeda_pipeline_disable(master, old->state);

//---- Secondary initialization.
        disable_done = (needs_phase2 || crtc->state->active) ?
                       NULL : &crtc->state->commit->flip_done;

//--- First using is here.
        /* wait phase 1 disable done */
        komeda_crtc_flush_and_wait_for_flip_done(kcrtc, disable_done);

So the first initialization with the delcaration is unnecessary.

And I also checked our internal testing branch which actually doesn't have
the first initialization. seems somethings wrong when lowry submit this to
upstream.

Hi Colin:

Thanks for the fix. I'll push it to drm-misc-fixes

Reviewed-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>

Best Regards
James