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Wed, 07 Oct 2020 13:23:58 +0100 MIME-Version: 1.0 Date: Wed, 07 Oct 2020 13:23:58 +0100 From: Marc Zyngier To: Thomas Gleixner Subject: Re: [PATCH v2 1/4] genirq/irqdomain: Allow partial trimming of irq_data hierarchy In-Reply-To: <738593a42b62ea7905e4a680775cb996@kernel.org> References: <20201006101137.1393797-1-maz@kernel.org> <20201006101137.1393797-2-maz@kernel.org> <87eemb6qdj.fsf@nanos.tec.linutronix.de> <10788c0d08fccbcbc1ac590a855e70d3@kernel.org> <738593a42b62ea7905e4a680775cb996@kernel.org> User-Agent: Roundcube Webmail/1.4.8 Message-ID: <02226efd42fdb249b81c01eb702100e9@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: tglx@linutronix.de, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, thierry.reding@gmail.com, jonathanh@nvidia.com, digetx@gmail.com, skomatineni@nvidia.com, vreddytalla@nvidia.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201007_082401_984186_9837BC9E X-CRM114-Status: GOOD ( 17.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Venkat Reddy Talla , linux-kernel@vger.kernel.org, Jonathan Hunter , Thierry Reding , Sowjanya Komatineni , linux-tegra@vger.kernel.org, Dmitry Osipenko , kernel-team@android.com, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-10-07 09:53, Marc Zyngier wrote: > On 2020-10-07 09:05, Marc Zyngier wrote: >> On 2020-10-06 21:39, Thomas Gleixner wrote: [...] >>> This is butt ugly, really. Especially the use case where the tegra >>> PMC >>> domain removes itself from the hierarchy from .alloc() >> >> I don't disagree at all. It is both horrible and dangerous. >> >> My preference would have been to split the PMC domain into discrete >> domains, each one having having its own depth. But that's incredibly >> hard to express in DT, and would break the combination of old/new >> DT and kernel. >> >>> That said, I don't have a better idea either. Sigh... >> >> A (very minor) improvement would be to turn the trim call in the PMC >> driver into >> a flag set in the first invalid irq_data structure, and let >> __irq_domain_alloc_irqs() do the dirty work. >> >> Still crap, but at least would prevent some form of abuse. Thoughts? > > Actually, I wonder whether we can have a more general approach: > > A partial hierarchy that doesn't have an irq_data->chip pointer > populated > cannot be valid. So I wonder if the least ugly thing to do is to just > drop > any messing about in the PMC driver, and instead to let > __irq_domain_alloc_irqs() > do the culling, always, by looking for a NULL pointer in > irq_data->chip. > > Not any less ugly, but at least doesn't need any driver intervention. [still talking to myself...] I implemented that, and it has the advantage of placing the hack in a single location. It even booted on a garden variety of systems. I'll post an updated series, and we can compare the various levels of ugliness. M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel