7e08baf6a8
On s390 systems (aka mainframes), it has classic channel devices for networking and permanent storage that are currently even more common than PCI devices. Hence it could have a fully functional s390 kernel with CONFIG_PCI=n, then the relevant iomem mapping functions [including ioremap(), devm_ioremap(), etc.] are not available. In LKP error report at below on s390: ------ ld: kernel/dma/coherent.o: in function `dma_init_coherent_memory': coherent.c:(.text+0x102): undefined reference to `memremap' ld: coherent.c:(.text+0x226): undefined reference to `memunmap' ld: kernel/dma/coherent.o: in function `dma_declare_coherent_memory': coherent.c:(.text+0x8b8): undefined reference to `memunmap' ld: kernel/dma/coherent.o: in function `dma_release_coherent_memory': coherent.c:(.text+0x9aa): undefined reference to `memunmap' ------ In the config file, several Kconfig options are: ------ '# CONFIG_PCI is not set' CONFIG_OF_EARLY_FLATTREE=y CONFIG_DMA_DECLARE_COHERENT=y ------ So, enabling OF_EARLY_FLATTREE will select DMA_DECLARE_COHERENT and cause above building errors even though they are not needed because CONFIG_PCI is disabled. Here let OF_EARLY_FLATTREE depend on HAS_IOMEM so that it won't be built to cause compiling error if PCI is unset. Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202306211329.ticOJCSv-lkp@intel.com/ Signed-off-by: Baoquan He <bhe@redhat.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Frank Rowand <frowand.list@gmail.com> Cc: devicetree@vger.kernel.org Link: https://lore.kernel.org/r/20230707135852.24292-9-bhe@redhat.com Signed-off-by: Rob Herring <robh@kernel.org>
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.