[RFC] libdrm: gralloc_handle.h: Fix build issue with Android

In trying to integrate the new gralloc_handle.h with the
drm_hwcomposer, I started seeing the following compilation
errors:

In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
        return handle;
               ^~~~~~
1 error generated.

This seems to be due to the gralloc_handle_create() definition
claiming to return a native_handle_t * type, rather then a
gralloc_handle_t *, which is what the code actually returns.

This function isn't actually used in the current drm_hwcomposer,
so I'm not totally sure that this fix is correct (rather then
returning the gralloc_handle_t's embadedded native_handle_t ptr).

But it seems something like this is needed.

Cc: Robert Foss <robert.foss@collabora.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sean Paul <seanpaul@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

---
 android/gralloc_handle.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

-- 
2.7.4

Hey John,

On Fri, Mar 16, 2018 at 10:48 PM, John Stultz <john.stultz@linaro.org> wrote:
> In trying to integrate the new gralloc_handle.h with the
> drm_hwcomposer, I started seeing the following compilation
> errors:
>
> In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
> external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
>         return handle;
>                ^~~~~~
> 1 error generated.
>
> This seems to be due to the gralloc_handle_create() definition
> claiming to return a native_handle_t * type, rather then a
> gralloc_handle_t *, which is what the code actually returns.
>
> This function isn't actually used in the current drm_hwcomposer,
> so I'm not totally sure that this fix is correct (rather then
> returning the gralloc_handle_t's embadedded native_handle_t ptr).

This changed in 009634e49309 ("android: fix gralloc_handle_create() problems")
to make the return value from gralloc_handle_create opaque to its user.

Since the only one that would use gralloc_handle_create is the gralloc
implementation itself (and libdrm isn't one) and using getters/setters was
rejected (IIRC), I would think there is no reason to obscure the return type.
Since buffer_handle_t is native_handle_t* is gralloc_handle_t* it's also
correct. The alternative to changing the declaration here is returning
nhandle instead of handle.

Adding Rob Herring who authored 009634e49309.

Thanks,
Stefan

Hey John,

On 03/16/2018 10:48 PM, John Stultz wrote:
> In trying to integrate the new gralloc_handle.h with the
> drm_hwcomposer, I started seeing the following compilation
> errors:
> 
> In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
> external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
>          return handle;
>                 ^~~~~~
> 1 error generated.
> 
> This seems to be due to the gralloc_handle_create() definition
> claiming to return a native_handle_t * type, rather then a
> gralloc_handle_t *, which is what the code actually returns.
> 
> This function isn't actually used in the current drm_hwcomposer,
> so I'm not totally sure that this fix is correct (rather then
> returning the gralloc_handle_t's embadedded native_handle_t ptr).
> 
> But it seems something like this is needed.
> 
> Cc: Robert Foss <robert.foss@collabora.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Sean Paul <seanpaul@google.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>   android/gralloc_handle.h | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/android/gralloc_handle.h b/android/gralloc_handle.h
> index 9cb5a5d..6e925c9 100644
> --- a/android/gralloc_handle.h
> +++ b/android/gralloc_handle.h
> @@ -84,7 +84,7 @@ static inline struct gralloc_handle_t *gralloc_handle(buffer_handle_t handle)
>   /**
>    * Create a buffer handle.
>    */
> -static inline native_handle_t *gralloc_handle_create(int32_t width,
> +static inline gralloc_handle_t *gralloc_handle_create(int32_t width,
>                                                        int32_t height,
>                                                        int32_t hal_format,
>                                                        int32_t usage)
> @@ -107,5 +107,4 @@ static inline native_handle_t *gralloc_handle_create(int32_t width,
>   
>   	return handle;
>   }
> -
>   #endif
> 

The gralloc_handle_t regturn type seems to be the correct one to me.

This patch is:
Reviewed-by: Robert Foss <robert.foss@collabora.com>

On Sat, Mar 17, 2018 at 2:33 PM, Stefan Schake <stschake@gmail.com> wrote:
> Hey John,
>
> On Fri, Mar 16, 2018 at 10:48 PM, John Stultz <john.stultz@linaro.org> wrote:
>> In trying to integrate the new gralloc_handle.h with the
>> drm_hwcomposer, I started seeing the following compilation
>> errors:
>>
>> In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
>> external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
>>         return handle;
>>                ^~~~~~
>> 1 error generated.

Somehow this is not throwing an error for me...

>> This seems to be due to the gralloc_handle_create() definition
>> claiming to return a native_handle_t * type, rather then a
>> gralloc_handle_t *, which is what the code actually returns.
>>
>> This function isn't actually used in the current drm_hwcomposer,
>> so I'm not totally sure that this fix is correct (rather then
>> returning the gralloc_handle_t's embadedded native_handle_t ptr).
>
> This changed in 009634e49309 ("android: fix gralloc_handle_create() problems")
> to make the return value from gralloc_handle_create opaque to its user.
>
> Since the only one that would use gralloc_handle_create is the gralloc
> implementation itself (and libdrm isn't one) and using getters/setters was
> rejected (IIRC), I would think there is no reason to obscure the return type.

Not rejected, just not required at the start and not in a lib. And I
am working on adding helper functions and I'm using buffer_handle_t
everywhere.

> Since buffer_handle_t is native_handle_t* is gralloc_handle_t* it's also
> correct. The alternative to changing the declaration here is returning
> nhandle instead of handle.

BTW, returning buffer_handle_t doesn't work though because it is const.

Rob

On Wed, Mar 28, 2018 at 10:19 AM, Rob Herring <robh@kernel.org> wrote:
> On Sat, Mar 17, 2018 at 2:33 PM, Stefan Schake <stschake@gmail.com> wrote:
>> Hey John,
>>
>> On Fri, Mar 16, 2018 at 10:48 PM, John Stultz <john.stultz@linaro.org> wrote:
>>> In trying to integrate the new gralloc_handle.h with the
>>> drm_hwcomposer, I started seeing the following compilation
>>> errors:
>>>
>>> In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
>>> external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
>>>         return handle;
>>>                ^~~~~~
>>> 1 error generated.
>
> Somehow this is not throwing an error for me...

NM. I have it fixed in a subsequent change in my tree...

2018-03-28 23:22 GMT+08:00 Rob Herring <robh@kernel.org>:
> On Wed, Mar 28, 2018 at 10:19 AM, Rob Herring <robh@kernel.org> wrote:
>> On Sat, Mar 17, 2018 at 2:33 PM, Stefan Schake <stschake@gmail.com> wrote:
>>> Hey John,
>>>
>>> On Fri, Mar 16, 2018 at 10:48 PM, John Stultz <john.stultz@linaro.org> wrote:
>>>> In trying to integrate the new gralloc_handle.h with the
>>>> drm_hwcomposer, I started seeing the following compilation
>>>> errors:
>>>>
>>>> In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
>>>> external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
>>>>         return handle;
>>>>                ^~~~~~
>>>> 1 error generated.
>>
>> Somehow this is not throwing an error for me...
>
> NM. I have it fixed in a subsequent change in my tree...

Hi,
I saw the same error after updated to libdrm master branch.
Could John's fix be merged?
Or maybe Rob has a better fix?

Hey Chih-Wei,

Thanks for the poke, the patch has been pushed now.


Rob.

On 04/03/2018 04:58 AM, Chih-Wei Huang wrote:
> 2018-03-28 23:22 GMT+08:00 Rob Herring <robh@kernel.org>:
>> On Wed, Mar 28, 2018 at 10:19 AM, Rob Herring <robh@kernel.org> wrote:
>>> On Sat, Mar 17, 2018 at 2:33 PM, Stefan Schake <stschake@gmail.com> wrote:
>>>> Hey John,
>>>>
>>>> On Fri, Mar 16, 2018 at 10:48 PM, John Stultz <john.stultz@linaro.org> wrote:
>>>>> In trying to integrate the new gralloc_handle.h with the
>>>>> drm_hwcomposer, I started seeing the following compilation
>>>>> errors:
>>>>>
>>>>> In file included from external/drm_hwcomposer/platformdrmgeneric.cpp:28:
>>>>> external/libdrm/android/gralloc_handle.h:108:9: error: cannot initialize return object of type 'native_handle_t *' (aka 'native_handle *') with an lvalue of type 'struct gralloc_handle_t *'
>>>>>          return handle;
>>>>>                 ^~~~~~
>>>>> 1 error generated.
>>>
>>> Somehow this is not throwing an error for me...
>>
>> NM. I have it fixed in a subsequent change in my tree...
> 
> Hi,
> I saw the same error after updated to libdrm master branch.
> Could John's fix be merged?
> Or maybe Rob has a better fix?
> 
>