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NO_IRQ is a relic from the old days. It is not used anymore in core functions. By the way, function irq_of_parse_and_map() returns value 0 on error. In some drivers, NO_IRQ is erroneously used to check the return of irq_of_parse_and_map(). It is not a real bug today because the only architectures using the drivers being fixed by this patch define NO_IRQ as 0, but there are architectures which define NO_IRQ as -1. If one day those architectures start using the non fixed drivers, there will be a problem. Long time ago Linus advocated for not using NO_IRQ, see https://lore.kernel.org/all/Pine.LNX.4.64.0511211150040.13959@g5.osdl.org He re-iterated the same view recently in https://lore.kernel.org/all/CAHk-=wg2Pkb9kbfbstbB91AJA2SF6cySbsgHG-iQMq56j3VTcA@mail.gmail.com So test !irq instead of tesing irq == NO_IRQ. All other usage of NO_IRQ for powerpc were removed in previous cycles so the time has come to remove NO_IRQ completely for powerpc. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/4b8d4f96140af01dec3a3330924dda8b2451c316.1674476798.git.christophe.leroy@csgroup.eu
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.