linux-kernel - Re: [PATCH v2] drm/panthor: Fix couple of NULL vs IS

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Message-ID: <b35d0de5-be46-42a1-b7e7-b24a72d945c7@oracle.com>
Date: Tue, 2 Apr 2024 19:35:41 +0530
From: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To: Boris Brezillon <boris.brezillon@...labora.com>
Cc: Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Heiko Stuebner <heiko@...ech.de>,
        Grant Likely <grant.likely@...aro.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com
Subject: Re: [PATCH v2] drm/panthor: Fix couple of NULL vs IS_ERR() bugs

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@...cle.com> 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@...cle.com>
>> ---
>> 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@oracle.com/

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
> 
>