Re: [PATCH libdrm 2/2] amdgpu: Use char* pointers in amdgpu_find_bo_by_cpu_mapping

["Zhang, Jerry (Junwei)" <Jerry.Zhang-5C7GfCeVMHo@public.gmane.org>]

On 08/14/2018 05:58 PM, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer@amd.com>
>
> Arithmetic using void* pointers isn't defined by the C standard, only as
> a GCC extension. Avoids compiler warnings:
>
> ../../amdgpu/amdgpu_bo.c: In function ‘amdgpu_find_bo_by_cpu_mapping’:
> ../../amdgpu/amdgpu_bo.c:554:48: warning: pointer of type ‘void *’ used in arithmetic [-Wpointer-arith]
>     if (cpu >= bo->cpu_ptr && cpu < (bo->cpu_ptr + bo->alloc_size))
>                                                  ^
> ../../amdgpu/amdgpu_bo.c:561:23: warning: pointer of type ‘void *’ used in subtraction [-Wpointer-arith]
>     *offset_in_bo = cpu - bo->cpu_ptr;
>                         ^
>
> Fixes: 4d454424e1f2 ("amdgpu: add a function to find bo by cpu mapping
>                       (v2)")
> Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
> ---
>   amdgpu/amdgpu.h    | 2 +-
>   amdgpu/amdgpu_bo.c | 7 ++++---
>   2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/amdgpu/amdgpu.h b/amdgpu/amdgpu.h
> index a8c353c6..f2bdeb95 100644
> --- a/amdgpu/amdgpu.h
> +++ b/amdgpu/amdgpu.h
> @@ -695,7 +695,7 @@ int amdgpu_create_bo_from_user_mem(amdgpu_device_handle dev,
>    *
>   */
>   int amdgpu_find_bo_by_cpu_mapping(amdgpu_device_handle dev,
> -				  void *cpu,
> +				  char *cpu,

Shall we cast the cpu pointer when do arithmetic and keep the arguments as other cpu ponter?

e.g.
@@ -565,14 +565,15 @@ int amdgpu_find_bo_by_cpu_mapping(amdgpu_device_handle dev,
                 bo = handle_table_lookup(&dev->bo_handles, i);
                 if (!bo || !bo->cpu_ptr || size > bo->alloc_size)
                         continue;
-               if (cpu >= bo->cpu_ptr && cpu < (bo->cpu_ptr + bo->alloc_size))
+               if (cpu >= bo->cpu_ptr &&
+                  (uint64_t)cpu < ((uint64_t)bo->cpu_ptr + bo->alloc_size))
                         break;
         }

         if (i < dev->bo_handles.max_key) {
                 atomic_inc(&bo->refcount);
                 *buf_handle = bo;
-               *offset_in_bo = cpu - bo->cpu_ptr;
+               *offset_in_bo = (uint64_t)cpu - (uint64_t)bo->cpu_ptr;
         } else {
                 *buf_handle = NULL;
                 *offset_in_bo = 0;

Regards,
Jerry

>   				  uint64_t size,
>   				  amdgpu_bo_handle *buf_handle,
>   				  uint64_t *offset_in_bo);
> diff --git a/amdgpu/amdgpu_bo.c b/amdgpu/amdgpu_bo.c
> index 86d1c143..ef75f1d0 100644
> --- a/amdgpu/amdgpu_bo.c
> +++ b/amdgpu/amdgpu_bo.c
> @@ -530,7 +530,7 @@ int amdgpu_bo_wait_for_idle(amdgpu_bo_handle bo,
>   }
>
>   int amdgpu_find_bo_by_cpu_mapping(amdgpu_device_handle dev,
> -				  void *cpu,
> +				  char *cpu,
>   				  uint64_t size,
>   				  amdgpu_bo_handle *buf_handle,
>   				  uint64_t *offset_in_bo)
> @@ -551,14 +551,15 @@ int amdgpu_find_bo_by_cpu_mapping(amdgpu_device_handle dev,
>   		bo = handle_table_lookup(&dev->bo_handles, i);
>   		if (!bo || !bo->cpu_ptr || size > bo->alloc_size)
>   			continue;
> -		if (cpu >= bo->cpu_ptr && cpu < (bo->cpu_ptr + bo->alloc_size))
> +		if (cpu >= (char*)bo->cpu_ptr &&
> +		    cpu < ((char*)bo->cpu_ptr + bo->alloc_size))
>   			break;
>   	}
>
>   	if (i < dev->bo_handles.max_key) {
>   		atomic_inc(&bo->refcount);
>   		*buf_handle = bo;
> -		*offset_in_bo = cpu - bo->cpu_ptr;
> +		*offset_in_bo = cpu - (char*)bo->cpu_ptr;
>   	} else {
>   		*buf_handle = NULL;
>   		*offset_in_bo = 0;
>
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