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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Nathan Chancellor <natechancellor@gmail.com>
Cc:     tehuang@realtek.com, yhchuang@realtek.com,
        linux-wireless@vger.kernel.org, clang-built-linux@googlegroups.com,
        arnd@arndb.de
Subject: Re: [PATCH 3/5] rtw88: add dump firmware fifo support
References: <20200925061219.23754-1-tehuang@realtek.com>
        <20200925061219.23754-4-tehuang@realtek.com>
        <20201001190641.GA3723966@ubuntu-m3-large-x86>
        <87d021cae2.fsf@codeaurora.org>
        <20201002084326.GA2013042@ubuntu-m3-large-x86>
Date:   Tue, 06 Oct 2020 08:53:04 +0300
In-Reply-To: <20201002084326.GA2013042@ubuntu-m3-large-x86> (Nathan
        Chancellor's message of "Fri, 2 Oct 2020 01:43:26 -0700")
Message-ID: <87y2kjc33z.fsf@codeaurora.org>
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Nathan Chancellor <natechancellor@gmail.com> writes:

> On Fri, Oct 02, 2020 at 11:14:29AM +0300, Kalle Valo wrote:
>> + arnd
>> 
>> Nathan Chancellor <natechancellor@gmail.com> writes:
>> 
>> >> +int rtw_fw_dump_fifo(struct rtw_dev *rtwdev, u8 fifo_sel, u32 addr, u32 size,
>> >> +		     u32 *buffer)
>> >> +{
>> >> +	if (!rtwdev->chip->fw_fifo_addr) {
>> >
>> > This causes a clang warning, which points out it is probably not doing
>> > what you think it is:
>> >
>> > drivers/net/wireless/realtek/rtw88/fw.c:1485:21: warning: address of
>> > array 'rtwdev->chip->fw_fifo_addr' will always evaluate to 'true'
>> > [-Wpointer-bool-conversion]
>> >         if (!rtwdev->chip->fw_fifo_addr) {
>> >             ~~~~~~~~~~~~~~~^~~~~~~~~~~~
>> > 1 warning generated.
>> >
>> > Was fw_fifo_addr[0] intended or should the check just be deleted?
>> 
>> BTW what is the easiest way to install clang for build testing the
>> kernel? For GCC I use crosstool[1] which is awesome as it makes the
>> installation so simple, do we have something similar for clang?
>> 
>> Just supporting x86 would be fine, as my use case would be just to
>> reproduce build warnings.
>> 
>> [1] https://mirrors.edge.kernel.org/pub/tools/crosstool/
>> 
>> -- 
>> https://patchwork.kernel.org/project/linux-wireless/list/
>> 
>> https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
>
> Unfortunately, we do not have anything for clang right now. It is on my
> TODO list but being a hobbyist, I have less time than I would like...
>
> If you do not mind building it from source, I maintain a Python script
> that tries to optimize building LLVM as much as possible by turning off
> things that the kernel does not care about so that the build is quick
> and it does not intrude or interfere with the host environment.
>
> Something like this should work to give you a stable clang toolchain
> that should work well for compiling the kernel:
>
> $ git clone https://github.com/ClangBuiltLinux/tc-build
> $ tc-build/build-llvm.py \
> --branch llvmorg-11.0.0-rc5 \
> --projects "clang;lld"
> $ tc-build/install/bin/clang --version | head -1
> ClangBuiltLinux clang version 11.0.0
> (https://github.com/llvm/llvm-project
> 60a25202a7dd1e00067fcfce512086ebf3788537)
>
> The script by default does a 2-stage build for optimization purposes; if
> you cannot spare many cycles, feel free to add
>
> --build-stage1-only --install-stage1-only
>
> to the build-llvm.py invocation. The toolchain is installed to "install"
> within the tc-build repo and it only requires a few external
> dependencies (outlined in the README) that it lets you know about before
> doing anything. Feel free to give it a shot and let me know if anything
> is broken.

Thanks, I'll try that when I have some free time.

> Otherwise, as long as your distribution has clang 10.0.1 or newer, it
> should be fine for compiling the kernel.

Good to know. My distro is old so I only have clang-8 available :)

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches