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Thu, 16 Oct 2025 07:39:34 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHoR3sOX166Tcf7MLH16gWKdUAYv0AI7cWSg6pn0j1tfmbyKX2QRAiCoA7ig0qK9oVKh4us1Q== X-Received: by 2002:a17:903:1a0b:b0:290:b14c:4f37 with SMTP id d9443c01a7336-290cb9475cfmr2112865ad.30.1760625573497; Thu, 16 Oct 2025 07:39:33 -0700 (PDT) Received: from zeus ([2405:6580:83a0:7600:6e93:a15a:9134:ae1f]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29099a7cec6sm32751745ad.55.2025.10.16.07.39.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Oct 2025 07:39:32 -0700 (PDT) Date: Thu, 16 Oct 2025 23:39:28 +0900 From: Ryosuke Yasuoka To: Greg KH Cc: arnd@arndb.de, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH rust-next v2 0/3] rust: miscdevice: add llseek support Message-ID: References: <20251015040246.151141-1-ryasuoka@redhat.com> <2025101544-stopper-rifling-00e0@gregkh> <2025101610-detention-dangle-cef6@gregkh> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <2025101610-detention-dangle-cef6@gregkh> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 19EkU9Rm52byfnUIOTqeBsXTQC86nRVoi2mgSUn8JVQ_1760625574 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Oct 16, 2025 at 01:24:12PM +0200, Greg KH wrote: > On Thu, Oct 16, 2025 at 07:19:51PM +0900, Ryosuke Yasuoka wrote: > > On Wed, Oct 15, 2025 at 07:40:12AM +0200, Greg KH wrote: > > > On Wed, Oct 15, 2025 at 01:02:40PM +0900, Ryosuke Yasuoka wrote: > > > > Hi all, > > > > > > > > This patch series add support for the llseek file operation to misc > > > > devices written in Rust. > > > > > > Cool, but what miscdevice driver needs llseek support? Do you have a > > > real user for this that we can see as well? > > > > Currently no. Because lseek is one of fundamental functions for device > > driver, I think it's valuable to add support. I believe we'll have real > > users based on read, write, and this lseek support. > > Char devices that use lseek are "odd", don't you agree? There are no > such current users under drivers/misc/ and only a rare few under > drivers/char/ (the huge user of that is mem.c but we aren't going to be > reimplementing that in rust any time soon...) > > So without a real user of this api, I suggest we hold-off on adding it. > Let's not add it until someone comes up with a very valid reason for it. Thank you for your review and clear explanation. I understand your point. It makes sense not to add this without real user. I'll hold off on this and will revisit it if a concrete use case emerges. Best regards, Ryosuke > thanks, > > greg k-h >