diff options
Diffstat (limited to 'drivers/gpu/nvgpu/include/nvgpu/types.h')
-rw-r--r-- | drivers/gpu/nvgpu/include/nvgpu/types.h | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/gpu/nvgpu/include/nvgpu/types.h b/drivers/gpu/nvgpu/include/nvgpu/types.h index 1e243e53..dfa95557 100644 --- a/drivers/gpu/nvgpu/include/nvgpu/types.h +++ b/drivers/gpu/nvgpu/include/nvgpu/types.h | |||
@@ -30,4 +30,32 @@ | |||
30 | #include <nvgpu_rmos/include/types.h> | 30 | #include <nvgpu_rmos/include/types.h> |
31 | #endif | 31 | #endif |
32 | 32 | ||
33 | /* | ||
34 | * These macros exist to make integer literals used in certain arithmetic | ||
35 | * operations explicitly large enough to hold the results of that operation. | ||
36 | * The following is an example of this. | ||
37 | * | ||
38 | * In MISRA the destination for a bitwise shift must be able to hold the number | ||
39 | * of bits shifted. Otherwise the results are undefined. For example: | ||
40 | * | ||
41 | * 256U << 20U | ||
42 | * | ||
43 | * This is valid C code but the results of this _may_ be undefined if the size | ||
44 | * of an unsigned by default is less than 24 bits (i.e 16 bits). The MISRA | ||
45 | * checker sees the 256U and determines that the 256U fits in a 16 bit data type | ||
46 | * (i.e a u16). Since a u16 has 16 bits, which is less than 20, this is an | ||
47 | * issue. | ||
48 | * | ||
49 | * Of course most compilers these days use 32 bits for the default unsigned type | ||
50 | * this is not a requirement. Moreover this same problem could exist like so: | ||
51 | * | ||
52 | * 0xfffffU << 40U | ||
53 | * | ||
54 | * The 0xfffffU is a 32 bit unsigned type; but we are shifting 40 bits which | ||
55 | * overflows the 32 bit data type. So in this case we need an explicit cast to | ||
56 | * 64 bits in order to prevent undefined behavior. | ||
57 | */ | ||
58 | #define U32(x) ((u32)(x)) | ||
59 | #define U64(x) ((u64)(x)) | ||
60 | |||
33 | #endif | 61 | #endif |