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

[Zhang, Jerry (Junwei)]

On 08/14/2018 05:58 PM, Michel Dänzer wrote:

From: Michel Dänzer <michel.daen...@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.daen...@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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