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[195.23.151.163]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48442d3b4f1sm4512147f8f.9.2026.09.01.06.48.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Sep 2026 06:48:49 -0700 (PDT) Sender: Julian Braha Message-ID: <0c445767-a4fa-4c44-b81a-64863be3de2d@gmail.com> Date: Tue, 1 Sep 2026 14:48:47 +0100 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults To: Geert Uytterhoeven Cc: nathan@kernel.org, nsc@kernel.org, xiang@kernel.org, chao@kernel.org, zbestahu@gmail.com, jefflexu@linux.alibaba.com, dhavale@google.com, hongbohbli@tencent.com, guochunhai@vivo.com, michael.bommarito@gmail.com, kees@kernel.org, vegard.nossum@oracle.com, sam@ravnborg.org, u.kleine-koenig@pengutronix.de, mmarek@suse.cz, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, "open list:SERIAL DRIVERS" , Arnd Bergmann , "Christophe Leroy (CS GROUP)" , mpe@ellerman.id.au References: <20260830221129.2668354-1-julianbraha@gmail.com> Content-Language: en-US From: Julian Braha In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit CC: Arnd, Christophe On 9/1/26 11:17, Geert Uytterhoeven wrote: > FTR, this will impact all defconfigs that restrict SERIAL_8250_NR_UARTS > to a value lower than 4: > > config SERIAL_8250_NR_UARTS > int "Maximum number of 8250/16550 serial ports" > depends on SERIAL_8250 > default "4" > > config SERIAL_8250_RUNTIME_UARTS > int "Number of 8250/16550 serial ports to register at runtime" > depends on SERIAL_8250 > range 0 SERIAL_8250_NR_UARTS > default "4" I suspected that there could be some cases where these out-of-range defaults were actually accidents and causing bugs, so I added a check with my SMT solver [1], which also detected these two (powerpc-only): config DATA_SHIFT int "Data shift" if DATA_SHIFT_BOOL default 24 if STRICT_KERNEL_RWX && PPC64 range 17 28 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32 range 14 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_8xx range 20 24 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_85xx default 22 if STRICT_KERNEL_RWX && PPC_BOOK3S_32 default 18 if (DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32 default 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_8xx && \ (PIN_TLB_DATA || PIN_TLB_TEXT) default 19 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_8xx default 24 if STRICT_KERNEL_RWX && PPC_85xx default PAGE_SHIFT config MODULES_SIZE int "Size of modules/execmem area (In Mbytes)" if MODULES_SIZE_BOOL range 1 256 if EXECMEM default 64 if EXECMEM && PPC_BOOK3S_32 default 32 if EXECMEM && PPC_8xx default 0 The DATA_SHIFT case may be bug, where it should be 12, but incorrectly adjusts to 20 when: PPC_85xx=y DEBUG_PAGEALLOC=y STRICT_KERNEL_RWX=n PAGE_SHIFT=12 The MODULES_SIZE case seems harmless since the only systems using that option are PPC_BOOK3S_32 and PPC_8xx. Anyway, this change to savedefconfig would also affect those 2. [1] https://github.com/julianbraha/kconfirm/tree/smt - Julian Braha