Messages in this thread |  | | From | Arnd Bergmann <> | Date | Tue, 14 Aug 2018 13:08:01 +0200 | Subject | Re: [PATCH] bitfield: avoid gcc-8 -Wint-in-bool-context warning |
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On Tue, Aug 14, 2018 at 12:04 PM David Laight <David.Laight@aculab.com> wrote: > > From: Johannes Berg > > Sent: 14 August 2018 08:57 > ... > > > How about fixing the root cause > > > in drivers/net/wireless/intel/iwlwifi/fw/api/rx.h ? > > > > > > > > > #define IWL_RX_HE_PHY_SIBG_SYM_OR_USER_NUM_MASK 0x1e00000000ULL > > > > > > > > > enum iwl_rx_he_phy looks really strange. > > > > Why? I don't think this is a problem, the enum is used here to get > > constants so that we can also have documentation for them. That's a > > common and accepted technique. > > It would be much more useful to indicate where the values are used. > Such a field/parameter could (probably) have the type of the enum. > But, at some point, the compiler might start barfing at that at well.
I think the compiler warning here only happens because one uses a compile-time constant expression that is not a numeric literal value into a boolean operator. That doesn't mean that there is something wrong with the enum in particular, or that enums cause a lot of issues elsewhere.
I would also argue that generally speaking the BUILD_BUG_ON_MSG() should try to either produce the specific build failure it was designed for, or not produce any output at all, rather than something that is more confusing to developers. If we want to enforce passing in number literals here, we should make that an explicit check, or otherwise allow any compile-time constant values.
> There are also a whole load of crappy __packed in that header file. > There might be one or two 64bit items on 32bit boundaries but > that can be solved without using __packed.
Agreed, this likely causes problems on architectures without unaligned load/store instructions that end up doing byte accesses to the descriptor fields, which in turn can confuse the hardware, and can become very slow when they live in dma_alloc_coherent() memory. That looks like a completely unrelated issue though.
Arnd
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