Re: [PATCH v2] drm/panthor: Fix couple of NULL vs IS_ERR() bugs

[Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>]

Hi Boris,
On 02/04/24 19:32, Boris Brezillon wrote:
> On Tue,  2 Apr 2024 06:47:08 -0700
> Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx> wrote:
>
> > 1. The devm_drm_dev_alloc() function returns error pointers.
> >     Update the error handling to check for error pointers instead of NULL.
> > 2. Currently panthor_vm_get_heap_pool() returns both ERR_PTR() and
> >     NULL(when create is false and if there is no poool attached to the
> >     VM)
> > 	- Change the function to return error pointers, when pool is
> > 	  NULL return -ENOENT
> > 	- Also handle the callers to check for IS_ERR() on failure.
> >
> > Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> > Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>
> > ---
> > This is spotted by smatch and the patch is only compile tested
> >
> > v1->v2: Fix the function panthor_vm_get_heap_pool() to only return error
> > pointers and handle the caller sites [Suggested by Boris Brezillon]
> > 	- Also merge these IS_ERR() vs NULL bugs into same patch
> > ---
> >   drivers/gpu/drm/panthor/panthor_drv.c   | 6 +++---
> >   drivers/gpu/drm/panthor/panthor_mmu.c   | 2 ++
> >   drivers/gpu/drm/panthor/panthor_sched.c | 2 +-
> >   3 files changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> > index 11b3ccd58f85..c8374cd4a30d 100644
> > --- a/drivers/gpu/drm/panthor/panthor_drv.c
> > +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> > @@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct drm_device *ddev, void *data,
> >   		return -EINVAL;
> >   
> >   	pool = panthor_vm_get_heap_pool(vm, false);
> > -	if (!pool) {
> > -		ret = -EINVAL;
> > +	if (IS_ERR(pool)) {
> > +		ret = PTR_ERR(pool);
> >   		goto out_put_vm;
> >   	}
> >   
> > @@ -1385,7 +1385,7 @@ static int panthor_probe(struct platform_device *pdev)
> >   
> >   	ptdev = devm_drm_dev_alloc(&pdev->dev, &panthor_drm_driver,
> >   				   struct panthor_device, base);
> > -	if (!ptdev)
> > +	if (IS_ERR(ptdev))
> >   		return -ENOMEM;
> >   
>
> Sorry, that one deserves a separate patch.

Ah okay, I was confused about the same.
So I will send a V3 removing that part and could you please use the 
independent patch that I sent before ?

https://lore.kernel.org/all/20240402104041.1689951-1-harshit.m.mogalapalli@xxxxxxxxxx/

Thanks,
Harshit

> >   	platform_set_drvdata(pdev, ptdev);
> > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> > index fdd35249169f..e1285cdb09ff 100644
> > --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> > @@ -1893,6 +1893,8 @@ struct panthor_heap_pool *panthor_vm_get_heap_pool(struct panthor_vm *vm, bool c
> >   			vm->heaps.pool = panthor_heap_pool_get(pool);
> >   	} else {
> >   		pool = panthor_heap_pool_get(vm->heaps.pool);
> > +		if (!pool)
> > +			pool = ERR_PTR(-ENOENT);
> >   	}
> >   	mutex_unlock(&vm->heaps.lock);
> >   
> > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> > index 5f7803b6fc48..617df2b980d0 100644
> > --- a/drivers/gpu/drm/panthor/panthor_sched.c
> > +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> > @@ -1343,7 +1343,7 @@ static int group_process_tiler_oom(struct panthor_group *group, u32 cs_id)
> >   	if (unlikely(csg_id < 0))
> >   		return 0;
> >   
> > -	if (!heaps || frag_end > vt_end || vt_end >= vt_start) {
> > +	if (IS_ERR(heaps) || frag_end > vt_end || vt_end >= vt_start) {
> >   		ret = -EINVAL;
> >   	} else {
> >   		/* We do the allocation without holding the scheduler lock to avoid