On 2024/03/11 18:08, Tang Yulong wrote:
> Hi, Kazu:
>
>> On 2024/03/01 17:48, Tao Liu wrote:
>>
>> hmm, as far as I know, not many kernels are configured with
>> CONFIG_IKCONFIG=y, e.g. RHEL kernels don't have it. so if it depends
>> only on ikconfig, it will not work on many kernels.
>>
>
> Thank you for the correction.
>
>> It's good to use ikconfig, but isn't there any other way?
>>
>> For example, it looks like it's always set to y on x86. so maybe we can
>> have a default value depending on architecture, for no ikconfig kernels.
>>
>> config X86
>> ...
>> select HAVE_EFFICIENT_UNALIGNED_ACCESS
>>
>> Thanks,
>> Kazu
>
> Yes, it seems that some architectures have this configuration enabled by
> default, such as ARM, ARM64, and X86. These are also commonly used
> architectures.
> So setting the default to CONFIG_Y for these architectures and CONFIG_N for
> others. Then, we can check whether IKCONFIG is enabled to retrieve the actual
> value. Do you think this is acceptable?
>
> like this:
>
> - bool efficient_unaligned_access =
> (get_kernel_config("CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS", NULL) ==
> IKCONFIG_Y);
> + bool efficient_unaligned_access;
> +
> +#if defined(ARM) || defined(ARM64) || defined(X86)
> + efficient_unaligned_access = true;
Yes. Looking at arch/*/Kconfig, it looks like the following
architectures will have 'y' IIUC, please use these.
X86, X86_64, ARM, ARM64, PPC, PPC64, S390, S390X
(LOONGARCH64 and RISCV64 can have 'n' depending on configs.)
With respect to lzo-rle user library, Tao is asking the kernel
developers. (Thanks Tao)
Thanks,
Kazu
> +#else
> + efficient_unaligned_access = false;
> +#endif
> +
> + if (kt->ikconfig_flags & IKCONFIG_AVAIL)
> + efficient_unaligned_access =
> (get_kernel_config("CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS", NULL) ==
> IKCONFIG_Y);
>
> Thanks,
> Yulong
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