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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4922fa96f0esm111413835e9.12.2026.06.16.13.05.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2026 13:05:27 -0700 (PDT) Date: Tue, 16 Jun 2026 21:05:25 +0100 From: David Laight To: Geert Uytterhoeven Cc: jkoolstra@xs4all.nl, brauner@kernel.org, broonie@kernel.org, cyphar@cyphar.com, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vfs: uapi: retire octal and hex numbers in favor of (1 << n) for O_ flags Message-ID: <20260616210525.1458974d@pumpkin> In-Reply-To: <20260616102250.3652779-1-geert+renesas@glider.be> References: <20260604222405.5382-1-jkoolstra@xs4all.nl> <20260616102250.3652779-1-geert+renesas@glider.be> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 16 Jun 2026 12:22:50 +0200 Geert Uytterhoeven wrote: > Hi Jori, > > > A recent build failure[1] exposed the diffculty of working with the > > current octal and hex definitions of O_ flags when trying to find a gap > > for a new flag. This difficulty is compounded by the fact that O_ flags > > may have architectural specific values. > > > > Replace the hex/octal #defines, which are hard to parse when looking for > > free bits, with explicit bit shifts like (1 << 11). Also, add comments > > that identify which architectures redefine some of the seemingly free > > ("cursed") bits in uapi/asm-generic/fcntl.h. These should not be used to > > define new O_ flags (for now, at least). > > > > The translastion was done with Claude Opus 4.8, and verified with a > > (non-AI) gawk script. The accounting of which architectures claim > > which bit-gaps in uapi/asm-generic/fcntl.h is also done by hand. > > > > [1]: https://lore.kernel.org/all/agruPPybCx8q2XcJ@sirena.org.uk/ > > > > Assisted-by: Claude:Opus 4.8 > > Signed-off-by: Jori Koolstra > > Thanks for your patch, which is now commit 0da79c259ad0554b ("vfs: > uapi: retire octal and hex numbers in favor of (1 << n) for O_ > flags"). > > > --- a/include/uapi/asm-generic/fcntl.h > > +++ b/include/uapi/asm-generic/fcntl.h > > @@ -15,51 +15,55 @@ > > * When introducing new O_* bits, please check its uniqueness in fcntl_init(). > > */ > > > > -#define O_ACCMODE 00000003 > > -#define O_RDONLY 00000000 > > -#define O_WRONLY 00000001 > > -#define O_RDWR 00000002 > > +#define O_ACCMODE 3 > > +#define O_RDONLY 0 > > +#define O_WRONLY (1 << 0) > > +#define O_RDWR (1 << 1) I'm not 100% that changing these uapi constants might not generate compile error for userspace that has duplicate definitions that are currently fine because the definitions exactly match. David > > And suddenly all these constants became signed? Can't that cause subtle > issues, especially for uapi headers? > > #define O_ACCMODE 3U > #define O_RDONLY 0 > #define O_WRONLY (1U << 0) > #define O_RDWR (1U << 1) > > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds >