src/nvidia/src/kernel/gpu/mem_mgr/heap.c:1607: unclear coding ? about open-gpu-kernel-modules HOT 4 OPEN

My read of the code is that currentBankInfo is indeed a bitfield. MEM_GROW_DOWN and MEM_GROW_UP are particular fields within it. From src/nvidia/generated/g_heap_nvoc.h:

// grow direction within a bank
#define BANK_MEM_GROW_UP                  0x00
#define BANK_MEM_GROW_DOWN                0x40
#define BANK_MEM_GROW_MASK                0x40

// grow direction if a bank placement fails
#define MEM_GROW_UP                       0x00
#define MEM_GROW_DOWN                     0x80
#define MEM_GROW_MASK                     0x80

Though the code could be clearer, bitwise AND has higher precedence than ternary ?:, so I don't believe the code is wrong.
https://en.cppreference.com/w/c/language/operator_precedence
Tagging as cosmetic.

from open-gpu-kernel-modules.

Whichever version is correct, I suggest use ( and ) to make the code more clear.

Better code is more clear code. We haven't got time or inclination to master fine details
of the C standard.

from open-gpu-kernel-modules.

both of them would reach the same result anyway. i suggest currentBankInfo = currentBankInfo & BANK_MEM_GROW_DOWN ? MEM_GROW_DOWN : MEM_GROW_UP; to clear any confusion

from open-gpu-kernel-modules.

looking at the previous section:

if (pVidHeapAlloc->flags & NVOS32_ALLOC_FLAGS_BANK_HINT)
{
    if (pVidHeapAlloc->flags & NVOS32_ALLOC_FLAGS_BANK_GROW_DOWN)
        currentBankInfo = MEM_GROW_DOWN;
    else
        currentBankInfo = MEM_GROW_UP;
    pVidHeapAlloc->flags &= ~(NVOS32_ALLOC_FLAGS_BANK_HINT); // hint flag only lasts for 1 loop
}
else
{
    currentBankInfo = (currentBankInfo & BANK_MEM_GROW_DOWN ? MEM_GROW_DOWN : MEM_GROW_UP);
}

it seems the original intent was to actually set currentBankInfo to MEM_GROW_DOWN or MEM_GROW_UP, not treat it like a bitfield?

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