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Wysocki" , linux-kernel@vger.kernel.org, Guo Ren , "H. Peter Anvin" , linux-riscv@lists.infradead.org, Will Deacon , Jonas Bonn , Florian Fainelli , Yoshinori Sato , linux-sh@vger.kernel.org, x86@kernel.org, Russell King , linux-csky@vger.kernel.org, Ingo Molnar , bcm-kernel-feedback-list@broadcom.com, Catalin Marinas , Palmer Dabbelt , devicetree@vger.kernel.org, Albert Ou , Ray Jui , Stefan Kristiansson , openrisc@lists.librecores.org, Borislav Petkov , Paul Walmsley , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Scott Branden , Greg Kroah-Hartman , Frank Rowand , James Morse , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 06/12] openrisc: Use of_get_cpu_hwid() Message-ID: References: <20211006164332.1981454-1-robh@kernel.org> <20211006164332.1981454-7-robh@kernel.org> <20211006212728.GM10333@gate.crashing.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211006212728.GM10333@gate.crashing.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211006_153743_939972_6C946BCE X-CRM114-Status: GOOD ( 19.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Segher, On Wed, Oct 06, 2021 at 04:27:28PM -0500, Segher Boessenkool wrote: > On Thu, Oct 07, 2021 at 05:44:00AM +0900, Stafford Horne wrote: > > You have defined of_get_cpu_hwid to return u64, will this create compiler > > warnings when since we are storing a u64 into a u32? > > > > It seems only if we make with W=3. > > Yes. This is done by -Wconversion, "Warn for implicit conversions that > may alter a value." Yeah, that is what I found out when I looked into it. > > I thought we usually warned on this. > > This warning is not in -Wall or -Wextra either, it suffers too much from > false positives. It is very natural to just ignore the high bits of > modulo types (which is what "unsigned" types *are*). Or the bits that > "fall off" on a conversion. The C standard makes this required > behaviour, it is useful, and it is the only convenient way of getting > this! Thanks for the background, It does make sense. I guess I was confused with java which requires casting when you store to a smaller size. I.e. Test.java:5: error: incompatible types: possible lossy conversion from int to short s = i; -Stafford _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel