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Currently, at probing time, the MSI domains of root buses are populated if either the information of MSI domain is available from firmware (DT or ACPI), or arch-specific sysdata is used to pass the fwnode of the MSI domain. These two conditions don't cover all, e.g. Hyper-V virtual PCI on ARM64, which doesn't have the MSI information in the firmware and couldn't use arch-specific sysdata because running on an architecture with PCI_DOMAINS_GENERIC=y. To support populating MSI domains of the root buses at the probing when neither of the above condition is true, the ->msi_domain of the corresponding bridge device is used: in pci_host_bridge_msi_domain(), which should return the MSI domain of the root bus, the ->msi_domain of the corresponding bridge is fetched first as a potential value of the MSI domain of the root bus. In order to use the approach to populate MSI domains, the driver needs to dev_set_msi_domain() on the bridge before calling pci_register_host_bridge(), and makes sure GENERIC_MSI_IRQ_DOMAIN=y. Another advantage of this new approach is providing an arch-independent way to populate MSI domains, which allows sharing the driver code as much as possible between architectures. Originally-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20210726180657.142727-3-boqun.feng@gmail.com Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.