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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d76eeb2d1sm13081378f8f.22.2026.04.13.06.01.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 06:01:11 -0700 (PDT) Date: Mon, 13 Apr 2026 14:01:09 +0100 From: David Laight To: "Arnd Bergmann" Cc: "Geert Uytterhoeven" , "Ping-Ke Shih" , "rtl8821cerfe2@gmail.com" , "kernel test robot" , "oe-kbuild-all@lists.linux.dev" , "linux-kernel@vger.kernel.org" Subject: Re: include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct rtw8814a_efuse) == 512" Message-ID: <20260413140109.2b20de7c@pumpkin> In-Reply-To: <6b6310b8-2b0d-4390-992e-5ccd81cef2e0@app.fastmail.com> References: <202604101721.fsv5XmCX-lkp@intel.com> <2fb2a553-3e67-497e-b964-7fa5f940e8a1@gmail.com> <1e02bd10a68747f4a342caedde76ef04@realtek.com> <6b6310b8-2b0d-4390-992e-5ccd81cef2e0@app.fastmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: oe-kbuild-all@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 13 Apr 2026 11:30:25 +0200 "Arnd Bergmann" wrote: > On Mon, Apr 13, 2026, at 11:15, Geert Uytterhoeven wrote: > > On Mon, 13 Apr 2026 at 02:48, Ping-Ke Shih wrote: > >> > On Fri, 10 Apr 2026 at 14:15, Ping-Ke Shih wrote: > >> > How can that make a difference? > >> > Both rtw8814au_efuse and rtw8814ae_efuse contain just (the same number > >> > of) bytes, so __packed on the union should not make any difference? > >> > Moreover, rtw8814au_efuse and rtw8814ae_efuse are already tagged with > >> > __packed, which should also not make any difference. Someone's been > >> > sprinkling too many __packed all over the place? > >> > >> I have similar thought as yours, but arm-linux-gnueabi-gcc compiler seems > >> have special treatment with union. For this case, without __packed > >> the offset of followed field res5 will become 0xe0. > > > > Hmm, I can confirm the original issue, and that adding __packed does > > have an impact (it reduces the size of rtw8814a_efuse from 522 to 520), > > but the actual size is still wrong (should be 512). > > > > drivers/net/wireless/realtek/rtw88/rtw88xxa.h has a similar issue, but > > adding __packed does not make a difference there. > > > > Removing the __packed from struct rtw8814au_efuse increases its size > > from 14 to 16 bytes. Looks like that ABI pads every structure to a > > multiple of 4 bytes? > > Correct, that is a unique property of the ARM "OABI" legacy ABI, > triggered by this defconfig line: > > # CONFIG_AEABI is not set > > Nobody should be using ARM OABI any more, and I think we should > remove it from the kernel once support for the StrongARM > CPU gets removed (I have patches for that), as those CPUs were > the last ones that regularly used OABI. That would definitely save all the annoyance of the otherwise pointless __packed. (I've seen it crop up before, but wasn't sure which architecture it was.) Doesn't OABI also have 32bit bool? > Annotating the union as '__packed' is the correct fix for > the theoretical users of OABI, and does nothing on other > supported targets in Linux. The other option is to ensure the specific drivers aren't ever compiled for !CONFIG_AEABI. Then it'll all get tidied up when you remove it. I read that the patches to remove 486 support have been merged. I'm sure it would have made sense to drop everything before P-Pro so that cmov can be used. David > > Arnd >