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Thu, 09 Apr 2026 16:41:22 -0700 (PDT) Received: from localhost ([2a00:79e0:2e7c:8:5d1f:ad34:cf0d:7e41]) by smtp.gmail.com with UTF8SMTPSA id a92af1059eb24-12c345b6208sm1610261c88.8.2026.04.09.16.41.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Apr 2026 16:41:21 -0700 (PDT) Date: Thu, 9 Apr 2026 16:41:20 -0700 From: Brian Norris To: Bjorn Helgaas Cc: Bjorn Helgaas , linux-kernel@vger.kernel.org, Lukas Wunner , Manivannan Sadhasivam , linux-pci@vger.kernel.org Subject: Re: [PATCH v2] PCI/portdrv: Allow probing even without child services Message-ID: References: <20260220164046.GA3528004@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Apr 09, 2026 at 04:20:27PM -0700, Brian Norris wrote: > So is pci_set_master() a one-way operation done in child services (never > call pci_clear_master()), and the only clear is via > pcie_portdrv_remove() -> pci_disable_device()? One other thought about this: it's actually a non-trivial question as to whether the port is actually going to use MSI (and therefore, need bus mastering). It depends on the result of pcie_init_service_irqs(), whether we succeed with MSI or INTx. We don't actually attempt to answer that question today. But if we did, we'd have to be scattering that code across all our IRQ-utilizing child services. I wonder if all that churn is worthwhile, when it's a relatively rare/strange case that a port really does *not* want bus mastering enabled. Brian