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[2003:d8:2f37:2b00:948c:dd9f:29c8:73f4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3d690f2ebb9sm5229370f8f.20.2025.09.01.08.31.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Sep 2025 08:31:04 -0700 (PDT) Message-ID: <4597944e-a8f5-44df-adf3-558940e88598@redhat.com> Date: Mon, 1 Sep 2025 17:31:01 +0200 Precedence: bulk X-Mailing-List: sparclinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 06/12] mm, s390: constify mapping related test functions for improved const-correctness To: Max Kellermann Cc: akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, willy@infradead.org, hughd@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, vishal.moola@gmail.com, linux@armlinux.org.uk, James.Bottomley@hansenpartnership.com, deller@gmx.de, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, andreas@gaisler.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, weixugc@google.com, baolin.wang@linux.alibaba.com, rientjes@google.com, shakeel.butt@linux.dev, thuth@redhat.com, broonie@kernel.org, osalvador@suse.de, jfalempe@redhat.com, mpe@ellerman.id.au, nysal@linux.ibm.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20250901123028.3383461-1-max.kellermann@ionos.com> <20250901123028.3383461-7-max.kellermann@ionos.com> <0bcb2d4d-9fb5-40c0-ab61-e021277a6ba3@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 01.09.25 17:22, Max Kellermann wrote: > On Mon, Sep 1, 2025 at 5:11 PM David Hildenbrand wrote: >>>> Should this also be *const ? >>> >>> No. These are function protoypes. A "const" on a parameter value >>> (pointer address, not pointed-to memory) makes no sense on a >>> prototype. >> >> But couldn't you argue the same about variable names? In most (not all >> :) ) we keep declaration + definition in sync. So thus my confusion. > > Variable names in the prototypes have no effect either, but they serve > as useful documentation. > > Whereas the "const" on a parameter value documents nothing - it's an > implementation detail whether the function would like to modify > parameter values. That implementation detail has no effect for the > caller. > > Of course, we could have "const" in the prototype as well. This boils > down to personal taste. It's not my taste (has no use, has no effect, > documents nothing, only adds noise for no gain), so I didn't add it. > If you prefer to have that, I'll leave my taste and home and add it, > but only after you guys make up your minds about whether you want to > have const parameters at all. Valid points. The problem is that it could very soon become inconsistent. For example, when I write a new function I usually just copy what I have from the definition into the declaration. For example, checkpatch complains about missing variable names and I think it complains when "extern" is used for functions. If we were to decide to go that route (not keep them in perfect sync), I guess it would be reasonable to extend checkpatch to warn if "*const" is used in a declaration. (perl magic, no idea how hard that would be) I'm sure there are false positives in the following: $ git grep "\*const" *.h | grep -v inline | wc -l 403 -- Cheers David / dhildenb