drm: Remove the deprecated drm_put_dev() function

  As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
it is already marked as deprecated, so remove it. No functional change.

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
 drivers/gpu/drm/drm_pci.c           |  3 ++-
 drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
 include/drm/drm_drv.h               |  1 -
 4 files changed, 4 insertions(+), 31 deletions(-)
  

On Sun, 25 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
> As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
> it is already marked as deprecated, so remove it. No functional change.
>
> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
> ---
>  drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>  drivers/gpu/drm/drm_pci.c           |  3 ++-
>  drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>  include/drm/drm_drv.h               |  1 -
>  4 files changed, 4 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 12687dd9e1ac..5057307fe22a 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>   * possibly leaving the hardware enabled.
>   */
>  
> -/**
> - * drm_put_dev - Unregister and release a DRM device
> - * @dev: DRM device
> - *
> - * Called at module unload time or when a PCI device is unplugged.
> - *
> - * Cleans up all DRM device, calling drm_lastclose().
> - *
> - * Note: Use of this function is deprecated. It will eventually go away
> - * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
> - * instead to make sure that the device isn't userspace accessible any more
> - * while teardown is in progress, ensuring that userspace can't access an
> - * inconsistent state.

The last sentence is the crucial one. While the patch has no functional
changes, I believe the goal never was to just mechanically replace one
call with the two.

BR,
Jani.


> - */
> -void drm_put_dev(struct drm_device *dev)
> -{
> -	DRM_DEBUG("\n");
> -
> -	if (!dev) {
> -		DRM_ERROR("cleanup called no dev\n");
> -		return;
> -	}
> -
> -	drm_dev_unregister(dev);
> -	drm_dev_put(dev);
> -}
> -EXPORT_SYMBOL(drm_put_dev);
> -
>  /**
>   * drm_dev_enter - Enter device critical section
>   * @dev: DRM device
> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
> index 39d35fc3a43b..b3a68a92eaa6 100644
> --- a/drivers/gpu/drm/drm_pci.c
> +++ b/drivers/gpu/drm/drm_pci.c
> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver,
>  					 legacy_dev_list) {
>  			if (dev->driver == driver) {
>  				list_del(&dev->legacy_dev_list);
> -				drm_put_dev(dev);
> +				drm_dev_unregister(dev);
> +				drm_dev_put(dev);
>  			}
>  		}
>  		mutex_unlock(&legacy_dev_list_lock);
> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
> index e4374814f0ef..a4955ae10659 100644
> --- a/drivers/gpu/drm/radeon/radeon_drv.c
> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>  {
>  	struct drm_device *dev = pci_get_drvdata(pdev);
>  
> -	drm_put_dev(dev);
> +	drm_dev_unregister(dev);
> +	drm_dev_put(dev);
>  }
>  
>  static void
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 89e2706cac56..289c97b12e82 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>  
>  void drm_dev_get(struct drm_device *dev);
>  void drm_dev_put(struct drm_device *dev);
> -void drm_put_dev(struct drm_device *dev);
>  bool drm_dev_enter(struct drm_device *dev, int *idx);
>  void drm_dev_exit(int idx);
>  void drm_dev_unplug(struct drm_device *dev);
  

Hi

Am 25.06.23 um 07:09 schrieb Sui Jingfeng:
> As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
> it is already marked as deprecated, so remove it. No functional change.
> 
> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
> ---
>   drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>   drivers/gpu/drm/drm_pci.c           |  3 ++-
>   drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>   include/drm/drm_drv.h               |  1 -
>   4 files changed, 4 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 12687dd9e1ac..5057307fe22a 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>    * possibly leaving the hardware enabled.
>    */
>   
> -/**
> - * drm_put_dev - Unregister and release a DRM device
> - * @dev: DRM device
> - *
> - * Called at module unload time or when a PCI device is unplugged.
> - *
> - * Cleans up all DRM device, calling drm_lastclose().
> - *
> - * Note: Use of this function is deprecated. It will eventually go away
> - * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
> - * instead to make sure that the device isn't userspace accessible any more
> - * while teardown is in progress, ensuring that userspace can't access an
> - * inconsistent state.
> - */
> -void drm_put_dev(struct drm_device *dev)
> -{
> -	DRM_DEBUG("\n");
> -
> -	if (!dev) {
> -		DRM_ERROR("cleanup called no dev\n");
> -		return;
> -	}
> -
> -	drm_dev_unregister(dev);
> -	drm_dev_put(dev);
> -}
> -EXPORT_SYMBOL(drm_put_dev);
> -
>   /**
>    * drm_dev_enter - Enter device critical section
>    * @dev: DRM device
> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
> index 39d35fc3a43b..b3a68a92eaa6 100644
> --- a/drivers/gpu/drm/drm_pci.c
> +++ b/drivers/gpu/drm/drm_pci.c
> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver,
>   					 legacy_dev_list) {
>   			if (dev->driver == driver) {
>   				list_del(&dev->legacy_dev_list);
> -				drm_put_dev(dev);
> +				drm_dev_unregister(dev);
> +				drm_dev_put(dev);
>   			}
>   		}
>   		mutex_unlock(&legacy_dev_list_lock);
> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
> index e4374814f0ef..a4955ae10659 100644
> --- a/drivers/gpu/drm/radeon/radeon_drv.c
> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>   {
>   	struct drm_device *dev = pci_get_drvdata(pdev);
>   
> -	drm_put_dev(dev);

Did you verify that dev cannot be NULL here? There was a check in 
drm_put_dev() for !dev.

Best regards
Thomas

> +	drm_dev_unregister(dev);
> +	drm_dev_put(dev);
>   }
>   
>   static void
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 89e2706cac56..289c97b12e82 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>   
>   void drm_dev_get(struct drm_device *dev);
>   void drm_dev_put(struct drm_device *dev);
> -void drm_put_dev(struct drm_device *dev);
>   bool drm_dev_enter(struct drm_device *dev, int *idx);
>   void drm_dev_exit(int idx);
>   void drm_dev_unplug(struct drm_device *dev);

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
  

Hi,

On 2023/6/26 15:56, Thomas Zimmermann wrote:
> Hi
>
> Am 25.06.23 um 07:09 schrieb Sui Jingfeng:
>> As this function can be replaced with drm_dev_unregister() + 
>> drm_dev_put(),
>> it is already marked as deprecated, so remove it. No functional change.
>>
>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
>> ---
>>   drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>>   drivers/gpu/drm/drm_pci.c           |  3 ++-
>>   drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>>   include/drm/drm_drv.h               |  1 -
>>   4 files changed, 4 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>> index 12687dd9e1ac..5057307fe22a 100644
>> --- a/drivers/gpu/drm/drm_drv.c
>> +++ b/drivers/gpu/drm/drm_drv.c
>> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>>    * possibly leaving the hardware enabled.
>>    */
>>   -/**
>> - * drm_put_dev - Unregister and release a DRM device
>> - * @dev: DRM device
>> - *
>> - * Called at module unload time or when a PCI device is unplugged.
>> - *
>> - * Cleans up all DRM device, calling drm_lastclose().
>> - *
>> - * Note: Use of this function is deprecated. It will eventually go away
>> - * completely.  Please use drm_dev_unregister() and drm_dev_put() 
>> explicitly
>> - * instead to make sure that the device isn't userspace accessible 
>> any more
>> - * while teardown is in progress, ensuring that userspace can't 
>> access an
>> - * inconsistent state.
>> - */
>> -void drm_put_dev(struct drm_device *dev)
>> -{
>> -    DRM_DEBUG("\n");
>> -
>> -    if (!dev) {
>> -        DRM_ERROR("cleanup called no dev\n");
>> -        return;
>> -    }
>> -
>> -    drm_dev_unregister(dev);
>> -    drm_dev_put(dev);
>> -}
>> -EXPORT_SYMBOL(drm_put_dev);
>> -
>>   /**
>>    * drm_dev_enter - Enter device critical section
>>    * @dev: DRM device
>> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
>> index 39d35fc3a43b..b3a68a92eaa6 100644
>> --- a/drivers/gpu/drm/drm_pci.c
>> +++ b/drivers/gpu/drm/drm_pci.c
>> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver 
>> *driver,
>>                        legacy_dev_list) {
>>               if (dev->driver == driver) {
>>                   list_del(&dev->legacy_dev_list);
>> -                drm_put_dev(dev);
>> +                drm_dev_unregister(dev);
>> +                drm_dev_put(dev);
>>               }
>>           }
>>           mutex_unlock(&legacy_dev_list_lock);
>> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c 
>> b/drivers/gpu/drm/radeon/radeon_drv.c
>> index e4374814f0ef..a4955ae10659 100644
>> --- a/drivers/gpu/drm/radeon/radeon_drv.c
>> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
>> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>>   {
>>       struct drm_device *dev = pci_get_drvdata(pdev);
>>   -    drm_put_dev(dev);
>
> Did you verify that dev cannot be NULL here? There was a check in 
> drm_put_dev() for !dev.
>

I have verified :


1)

If there is no radeon card(say R5-340) mounted in the system,  I 
modprobe the radeon.ko manually.

then both the radeon_pci_probe() and the radeon_pci_remove() function 
won't get called.

There is no chance that the driver_probe_device() function getting called.


|- driver_register()

|-- bus_add_driver()

|--- driver_attach()

|---- bus_for_each_dev(drv->bus, NULL, drv, __driver_attach)

|----- __driver_attach()

|------ __device_attach_driver()

// There is no chance that the driver_probe_device() function get called.

|------- driver_probe_device(drv, dev)

```


2)  normal case:


If there are radeon cards mounted in the system,

then as long as the pci_set_drvdata(pdev, dev) get called,

the 'driver_data' member of struct device will hold the pointer to the 
'struct drm_device';

So, it will be fine as long as the radeon.ko get loaded normally.


I'm sure it will works as expected on normal case, with 100% confident.


3) Abnormal case

If there is a error happen before the 'pci_set_drvdata(pdev, dev)' 
function get called.

It is also don't need to worry, if the ->probe() failed, then the 
->remove will be get called.


I have verified that

if the ->probe() failed, then the ->remove will be get called.

I'm doing the test by add a line before the drm_dev_alloc()

function in the body of radeon_pci_probe() function.

See below:

```

     return -ENODEV;

     dev = drm_dev_alloc(&kms_driver, &pdev->dev);
     if (IS_ERR(dev))
         return PTR_ERR(dev);

     ret = pci_enable_device(pdev);
     if (ret)
         goto err_free;
```


So, there is no problem, as far as I can see.


> Best regards
> Thomas
>
>> +    drm_dev_unregister(dev);
>> +    drm_dev_put(dev);
>>   }
>>     static void
>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>> index 89e2706cac56..289c97b12e82 100644
>> --- a/include/drm/drm_drv.h
>> +++ b/include/drm/drm_drv.h
>> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>     void drm_dev_get(struct drm_device *dev);
>>   void drm_dev_put(struct drm_device *dev);
>> -void drm_put_dev(struct drm_device *dev);
>>   bool drm_dev_enter(struct drm_device *dev, int *idx);
>>   void drm_dev_exit(int idx);
>>   void drm_dev_unplug(struct drm_device *dev);
>
  

Hi,

On 2023/6/26 15:48, Jani Nikula wrote:
> On Sun, 25 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
>> As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
>> it is already marked as deprecated, so remove it. No functional change.
>>
>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
>> ---
>>   drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>>   drivers/gpu/drm/drm_pci.c           |  3 ++-
>>   drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>>   include/drm/drm_drv.h               |  1 -
>>   4 files changed, 4 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>> index 12687dd9e1ac..5057307fe22a 100644
>> --- a/drivers/gpu/drm/drm_drv.c
>> +++ b/drivers/gpu/drm/drm_drv.c
>> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>>    * possibly leaving the hardware enabled.
>>    */
>>   
>> -/**
>> - * drm_put_dev - Unregister and release a DRM device
>> - * @dev: DRM device
>> - *
>> - * Called at module unload time or when a PCI device is unplugged.
>> - *
>> - * Cleans up all DRM device, calling drm_lastclose().
>> - *
>> - * Note: Use of this function is deprecated. It will eventually go away
>> - * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
>> - * instead to make sure that the device isn't userspace accessible any more
>> - * while teardown is in progress, ensuring that userspace can't access an
>> - * inconsistent state.
> The last sentence is the crucial one. While the patch has no functional
> changes,

But my patch help to save a useless check(if (!dev))

on where we found the check is not necessary.

```

-	if (!dev) {
-		DRM_ERROR("cleanup called no dev\n");
-		return;
-	}

```


> I believe the goal never was to just mechanically replace one
> call with the two.

The DRM core lose nothing, just a function wrapper.

Instead, this is probably a good chance to migrate the burden to the 
driver side.

I think the device driver(drm/radeon, for example) have better understanding

about how to ensure that userspace can't access an inconsistent state 
than the DRM core.

>
> BR,
> Jani.
>
>
>> - */
>> -void drm_put_dev(struct drm_device *dev)
>> -{
>> -	DRM_DEBUG("\n");
>> -
>> -	if (!dev) {
>> -		DRM_ERROR("cleanup called no dev\n");
>> -		return;
>> -	}
>> -
>> -	drm_dev_unregister(dev);
>> -	drm_dev_put(dev);
>> -}
>> -EXPORT_SYMBOL(drm_put_dev);
>> -
>>   /**
>>    * drm_dev_enter - Enter device critical section
>>    * @dev: DRM device
>> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
>> index 39d35fc3a43b..b3a68a92eaa6 100644
>> --- a/drivers/gpu/drm/drm_pci.c
>> +++ b/drivers/gpu/drm/drm_pci.c
>> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver,
>>   					 legacy_dev_list) {
>>   			if (dev->driver == driver) {
>>   				list_del(&dev->legacy_dev_list);
>> -				drm_put_dev(dev);
>> +				drm_dev_unregister(dev);
>> +				drm_dev_put(dev);
>>   			}
>>   		}
>>   		mutex_unlock(&legacy_dev_list_lock);
>> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
>> index e4374814f0ef..a4955ae10659 100644
>> --- a/drivers/gpu/drm/radeon/radeon_drv.c
>> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
>> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>>   {
>>   	struct drm_device *dev = pci_get_drvdata(pdev);
>>   
>> -	drm_put_dev(dev);
>> +	drm_dev_unregister(dev);
>> +	drm_dev_put(dev);
>>   }
>>   
>>   static void
>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>> index 89e2706cac56..289c97b12e82 100644
>> --- a/include/drm/drm_drv.h
>> +++ b/include/drm/drm_drv.h
>> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>   
>>   void drm_dev_get(struct drm_device *dev);
>>   void drm_dev_put(struct drm_device *dev);
>> -void drm_put_dev(struct drm_device *dev);
>>   bool drm_dev_enter(struct drm_device *dev, int *idx);
>>   void drm_dev_exit(int idx);
>>   void drm_dev_unplug(struct drm_device *dev);
  

On Tue, 27 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
> Hi,
>
> On 2023/6/26 15:48, Jani Nikula wrote:
>> On Sun, 25 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
>>> As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
>>> it is already marked as deprecated, so remove it. No functional change.
>>>
>>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
>>> ---
>>>   drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>>>   drivers/gpu/drm/drm_pci.c           |  3 ++-
>>>   drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>>>   include/drm/drm_drv.h               |  1 -
>>>   4 files changed, 4 insertions(+), 31 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>> index 12687dd9e1ac..5057307fe22a 100644
>>> --- a/drivers/gpu/drm/drm_drv.c
>>> +++ b/drivers/gpu/drm/drm_drv.c
>>> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>>>    * possibly leaving the hardware enabled.
>>>    */
>>>   
>>> -/**
>>> - * drm_put_dev - Unregister and release a DRM device
>>> - * @dev: DRM device
>>> - *
>>> - * Called at module unload time or when a PCI device is unplugged.
>>> - *
>>> - * Cleans up all DRM device, calling drm_lastclose().
>>> - *
>>> - * Note: Use of this function is deprecated. It will eventually go away
>>> - * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
>>> - * instead to make sure that the device isn't userspace accessible any more
>>> - * while teardown is in progress, ensuring that userspace can't access an
>>> - * inconsistent state.
>> The last sentence is the crucial one. While the patch has no functional
>> changes,
>
> But my patch help to save a useless check(if (!dev))
>
> on where we found the check is not necessary.
>
> ```
>
> -	if (!dev) {
> -		DRM_ERROR("cleanup called no dev\n");
> -		return;
> -	}
>
> ```
>
>
>> I believe the goal never was to just mechanically replace one
>> call with the two.
>
> The DRM core lose nothing, just a function wrapper.
>
> Instead, this is probably a good chance to migrate the burden to the 
> driver side.

The point is to *fix* this stuff while doing the conversion. Anyone can
replace one function call with two, but that's just brushing the problem
under the carpet.

The current state is that we have a function the use of which is
potentially problematic, it's documented, and we can trivially locate
all the call sites.

After your change, we've lost that information, and we haven't fixed
anything.


BR,
Jani.


>
> I think the device driver(drm/radeon, for example) have better understanding
>
> about how to ensure that userspace can't access an inconsistent state 
> than the DRM core.
>
>>
>> BR,
>> Jani.
>>
>>
>>> - */
>>> -void drm_put_dev(struct drm_device *dev)
>>> -{
>>> -	DRM_DEBUG("\n");
>>> -
>>> -	if (!dev) {
>>> -		DRM_ERROR("cleanup called no dev\n");
>>> -		return;
>>> -	}
>>> -
>>> -	drm_dev_unregister(dev);
>>> -	drm_dev_put(dev);
>>> -}
>>> -EXPORT_SYMBOL(drm_put_dev);
>>> -
>>>   /**
>>>    * drm_dev_enter - Enter device critical section
>>>    * @dev: DRM device
>>> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
>>> index 39d35fc3a43b..b3a68a92eaa6 100644
>>> --- a/drivers/gpu/drm/drm_pci.c
>>> +++ b/drivers/gpu/drm/drm_pci.c
>>> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver,
>>>   					 legacy_dev_list) {
>>>   			if (dev->driver == driver) {
>>>   				list_del(&dev->legacy_dev_list);
>>> -				drm_put_dev(dev);
>>> +				drm_dev_unregister(dev);
>>> +				drm_dev_put(dev);
>>>   			}
>>>   		}
>>>   		mutex_unlock(&legacy_dev_list_lock);
>>> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
>>> index e4374814f0ef..a4955ae10659 100644
>>> --- a/drivers/gpu/drm/radeon/radeon_drv.c
>>> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
>>> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>>>   {
>>>   	struct drm_device *dev = pci_get_drvdata(pdev);
>>>   
>>> -	drm_put_dev(dev);
>>> +	drm_dev_unregister(dev);
>>> +	drm_dev_put(dev);
>>>   }
>>>   
>>>   static void
>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>>> index 89e2706cac56..289c97b12e82 100644
>>> --- a/include/drm/drm_drv.h
>>> +++ b/include/drm/drm_drv.h
>>> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>>   
>>>   void drm_dev_get(struct drm_device *dev);
>>>   void drm_dev_put(struct drm_device *dev);
>>> -void drm_put_dev(struct drm_device *dev);
>>>   bool drm_dev_enter(struct drm_device *dev, int *idx);
>>>   void drm_dev_exit(int idx);
>>>   void drm_dev_unplug(struct drm_device *dev);
  

Hi

On 2023/6/27 17:33, Jani Nikula wrote:
> On Tue, 27 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
>> Hi,
>>
>> On 2023/6/26 15:48, Jani Nikula wrote:
>>> On Sun, 25 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
>>>> As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
>>>> it is already marked as deprecated, so remove it. No functional change.
>>>>
>>>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
>>>> ---
>>>>    drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>>>>    drivers/gpu/drm/drm_pci.c           |  3 ++-
>>>>    drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>>>>    include/drm/drm_drv.h               |  1 -
>>>>    4 files changed, 4 insertions(+), 31 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>>> index 12687dd9e1ac..5057307fe22a 100644
>>>> --- a/drivers/gpu/drm/drm_drv.c
>>>> +++ b/drivers/gpu/drm/drm_drv.c
>>>> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>>>>     * possibly leaving the hardware enabled.
>>>>     */
>>>>    
>>>> -/**
>>>> - * drm_put_dev - Unregister and release a DRM device
>>>> - * @dev: DRM device
>>>> - *
>>>> - * Called at module unload time or when a PCI device is unplugged.
>>>> - *
>>>> - * Cleans up all DRM device, calling drm_lastclose().
>>>> - *
>>>> - * Note: Use of this function is deprecated. It will eventually go away
>>>> - * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
>>>> - * instead to make sure that the device isn't userspace accessible any more
>>>> - * while teardown is in progress, ensuring that userspace can't access an
>>>> - * inconsistent state.
>>> The last sentence is the crucial one. While the patch has no functional
>>> changes,
>> But my patch help to save a useless check(if (!dev))
>>
>> on where we found the check is not necessary.
>>
>> ```
>>
>> -	if (!dev) {
>> -		DRM_ERROR("cleanup called no dev\n");
>> -		return;
>> -	}
>>
>> ```
>>
>>
>>> I believe the goal never was to just mechanically replace one
>>> call with the two.
>> The DRM core lose nothing, just a function wrapper.
>>
>> Instead, this is probably a good chance to migrate the burden to the
>> driver side.
> The point is to *fix* this stuff while doing the conversion. Anyone can
> replace one function call with two, but that's just brushing the problem
> under the carpet.

Well,  drm/i915 don't call this function either.

Only the drm/radeon call this function.

> The current state is that we have a function the use of which is
> potentially problematic, it's documented, and we can trivially locate
> all the call sites.

But I do agree with you that the comments of this function are sort of 
good quality document.

> After your change, we've lost that information, and we haven't fixed
> anything.

But back to the technique question, is it true that

the drm_dev_unregister() function alone can't guarantee

the device isn't userspace accessible any more ?

>
> BR,
> Jani.
>
>
>> I think the device driver(drm/radeon, for example) have better understanding
>>
>> about how to ensure that userspace can't access an inconsistent state
>> than the DRM core.
>>
>>> BR,
>>> Jani.
>>>
>>>
>>>> - */
>>>> -void drm_put_dev(struct drm_device *dev)
>>>> -{
>>>> -	DRM_DEBUG("\n");
>>>> -
>>>> -	if (!dev) {
>>>> -		DRM_ERROR("cleanup called no dev\n");
>>>> -		return;
>>>> -	}
>>>> -
>>>> -	drm_dev_unregister(dev);
>>>> -	drm_dev_put(dev);
>>>> -}
>>>> -EXPORT_SYMBOL(drm_put_dev);
>>>> -
>>>>    /**
>>>>     * drm_dev_enter - Enter device critical section
>>>>     * @dev: DRM device
>>>> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
>>>> index 39d35fc3a43b..b3a68a92eaa6 100644
>>>> --- a/drivers/gpu/drm/drm_pci.c
>>>> +++ b/drivers/gpu/drm/drm_pci.c
>>>> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver,
>>>>    					 legacy_dev_list) {
>>>>    			if (dev->driver == driver) {
>>>>    				list_del(&dev->legacy_dev_list);
>>>> -				drm_put_dev(dev);
>>>> +				drm_dev_unregister(dev);
>>>> +				drm_dev_put(dev);
>>>>    			}
>>>>    		}
>>>>    		mutex_unlock(&legacy_dev_list_lock);
>>>> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
>>>> index e4374814f0ef..a4955ae10659 100644
>>>> --- a/drivers/gpu/drm/radeon/radeon_drv.c
>>>> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
>>>> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>>>>    {
>>>>    	struct drm_device *dev = pci_get_drvdata(pdev);
>>>>    
>>>> -	drm_put_dev(dev);
>>>> +	drm_dev_unregister(dev);
>>>> +	drm_dev_put(dev);
>>>>    }
>>>>    
>>>>    static void
>>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>>>> index 89e2706cac56..289c97b12e82 100644
>>>> --- a/include/drm/drm_drv.h
>>>> +++ b/include/drm/drm_drv.h
>>>> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>>>    
>>>>    void drm_dev_get(struct drm_device *dev);
>>>>    void drm_dev_put(struct drm_device *dev);
>>>> -void drm_put_dev(struct drm_device *dev);
>>>>    bool drm_dev_enter(struct drm_device *dev, int *idx);
>>>>    void drm_dev_exit(int idx);
>>>>    void drm_dev_unplug(struct drm_device *dev);
  

On 2023/6/27 16:41, Sui Jingfeng wrote:
>
> if the ->probe() failed, then the ->remove will be get called. 


if the ->probe() failed, then the ->remove()  will *NOT* get called.
  

Hi,

On 2023/6/27 17:33, Jani Nikula wrote:
> On Tue, 27 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
>> Hi,
>>
>> On 2023/6/26 15:48, Jani Nikula wrote:
>>> On Sun, 25 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote:
>>>> As this function can be replaced with drm_dev_unregister() + drm_dev_put(),
>>>> it is already marked as deprecated, so remove it. No functional change.
>>>>
>>>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
>>>> ---
>>>>    drivers/gpu/drm/drm_drv.c           | 28 ----------------------------
>>>>    drivers/gpu/drm/drm_pci.c           |  3 ++-
>>>>    drivers/gpu/drm/radeon/radeon_drv.c |  3 ++-
>>>>    include/drm/drm_drv.h               |  1 -
>>>>    4 files changed, 4 insertions(+), 31 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>>> index 12687dd9e1ac..5057307fe22a 100644
>>>> --- a/drivers/gpu/drm/drm_drv.c
>>>> +++ b/drivers/gpu/drm/drm_drv.c
>>>> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor)
>>>>     * possibly leaving the hardware enabled.
>>>>     */
>>>>    
>>>> -/**
>>>> - * drm_put_dev - Unregister and release a DRM device
>>>> - * @dev: DRM device
>>>> - *
>>>> - * Called at module unload time or when a PCI device is unplugged.
>>>> - *
>>>> - * Cleans up all DRM device, calling drm_lastclose().
>>>> - *
>>>> - * Note: Use of this function is deprecated. It will eventually go away
>>>> - * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
>>>> - * instead to make sure that the device isn't userspace accessible any more
>>>> - * while teardown is in progress, ensuring that userspace can't access an
>>>> - * inconsistent state.
>>> The last sentence is the crucial one. While the patch has no functional
>>> changes,
>> But my patch help to save a useless check(if (!dev))
>>
>> on where we found the check is not necessary.
>>
>> ```
>>
>> -	if (!dev) {
>> -		DRM_ERROR("cleanup called no dev\n");
>> -		return;
>> -	}
>>
>> ```
>>
>>
>>> I believe the goal never was to just mechanically replace one
>>> call with the two.
>> The DRM core lose nothing, just a function wrapper.
>>
>> Instead, this is probably a good chance to migrate the burden to the
>> driver side.
> The point is to *fix* this stuff while doing the conversion. Anyone can
> replace one function call with two, but that's just brushing the problem
> under the carpet.

Interesting!

To be honest, I love you reviews.


I think, I probably be able to solve more practical problem,

This patch is just a trivial, I don't care much.


Can you help to have a look at my vgaarb patch set [1]

[1] https://patchwork.freedesktop.org/series/119250/

Really need you guidance there.


> The current state is that we have a function the use of which is
> potentially problematic, it's documented, and we can trivially locate
> all the call sites.

I can merge the document to comments of the drm_dev_unregister() function,

remove the drm_put_dev function only. What do you think about this?

> After your change, we've lost that information, and we haven't fixed
> anything.
>
My understanding is that drm_dev_unregister() alone is enough to stop 
the user-space

program accessing the kernel interface exposed.

```

radeon_pci_remove(struct pci_dev *pdev)

{

      // should be called first in the pci remove funcition

     drm_dev_unregister(dev);

     // do the various(necessary) cleanup and free resource allocated


     // call this function at the bottom of the radeon_pci_remove() function

     drm_dev_put(dev);

}

```


And the drm_dev_unregister() function already told us, see below:


```
/**
  * drm_dev_unregister - Unregister DRM device
  * @dev: Device to unregister
  *
  * Unregister the DRM device from the system. This does the reverse of
  * drm_dev_register() but does not deallocate the device. The caller 
must call
  * drm_dev_put() to drop their final reference, unless it is managed 
with devres
  * (as devices allocated with devm_drm_dev_alloc() are), in which case 
there is
  * already an unwind action registered.
  *
  * A special form of unregistering for hotpluggable devices is 
drm_dev_unplug(),
  * which can be called while there are still open users of @dev.
  *
  * This should be called first in the device teardown code to make sure
  * userspace can't access the device instance any more.
  */
void drm_dev_unregister(struct drm_device *dev)

...

```


Thanks for the interesting remark again.

> BR,
> Jani.
>
>
>> I think the device driver(drm/radeon, for example) have better understanding
>>
>> about how to ensure that userspace can't access an inconsistent state
>> than the DRM core.
>>
>>> BR,
>>> Jani.
>>>
>>>
>>>> - */
>>>> -void drm_put_dev(struct drm_device *dev)
>>>> -{
>>>> -	DRM_DEBUG("\n");
>>>> -
>>>> -	if (!dev) {
>>>> -		DRM_ERROR("cleanup called no dev\n");
>>>> -		return;
>>>> -	}
>>>> -
>>>> -	drm_dev_unregister(dev);
>>>> -	drm_dev_put(dev);
>>>> -}
>>>> -EXPORT_SYMBOL(drm_put_dev);
>>>> -
>>>>    /**
>>>>     * drm_dev_enter - Enter device critical section
>>>>     * @dev: DRM device
>>>> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
>>>> index 39d35fc3a43b..b3a68a92eaa6 100644
>>>> --- a/drivers/gpu/drm/drm_pci.c
>>>> +++ b/drivers/gpu/drm/drm_pci.c
>>>> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver,
>>>>    					 legacy_dev_list) {
>>>>    			if (dev->driver == driver) {
>>>>    				list_del(&dev->legacy_dev_list);
>>>> -				drm_put_dev(dev);
>>>> +				drm_dev_unregister(dev);
>>>> +				drm_dev_put(dev);
>>>>    			}
>>>>    		}
>>>>    		mutex_unlock(&legacy_dev_list_lock);
>>>> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
>>>> index e4374814f0ef..a4955ae10659 100644
>>>> --- a/drivers/gpu/drm/radeon/radeon_drv.c
>>>> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
>>>> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev)
>>>>    {
>>>>    	struct drm_device *dev = pci_get_drvdata(pdev);
>>>>    
>>>> -	drm_put_dev(dev);
>>>> +	drm_dev_unregister(dev);
>>>> +	drm_dev_put(dev);
>>>>    }
>>>>    
>>>>    static void
>>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>>>> index 89e2706cac56..289c97b12e82 100644
>>>> --- a/include/drm/drm_drv.h
>>>> +++ b/include/drm/drm_drv.h
>>>> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>>>    
>>>>    void drm_dev_get(struct drm_device *dev);
>>>>    void drm_dev_put(struct drm_device *dev);
>>>> -void drm_put_dev(struct drm_device *dev);
>>>>    bool drm_dev_enter(struct drm_device *dev, int *idx);
>>>>    void drm_dev_exit(int idx);
>>>>    void drm_dev_unplug(struct drm_device *dev);
  

Hi,

On 2023/6/27 16:41, Sui Jingfeng wrote:
> I have verified that
>
> if the ->probe() failed, then the ->remove will be get called.
>
Sorry,

if the ->probe() failed, then the ->remove() will *NOT* get called.


> I'm doing the test by add a line before the drm_dev_alloc()
>
I do the test by adding one line code before the drm_dev_alloc() function

  to generate a fault(error) manually,


>
> See below:
>
> ```
>
>     return -ENODEV;
>
>     dev = drm_dev_alloc(&kms_driver, &pdev->dev);
>     if (IS_ERR(dev))
>         return PTR_ERR(dev);
>
>     ret = pci_enable_device(pdev);
>     if (ret)
>         goto err_free;
> ```
>
>
> So, there is no problem, as far as I can see. 
All in all,  if the ->probe() failed, then the ->remove() will *NOT* get 
called.