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The COMEDI standalone 8255 driver can be used to configure a COMEDI device consisting of one of more subdevices, each using an 8255 digital I/O chip mapped to a range of port I/O addresses. The base port I/O address of each chip is specified in an array of integer option values by the `COMEDI_DEVCONFIG` ioctl. When support for multiple 8255 subdevices per device was added in the out-of-tree comedi 0.7.27 back in 1999, if any port I/O region could not be requested, then the corresponding subdevice was set to be an "unused" subdevice, and the COMEDI device would still be set-up OK as long as those were the only types of errors. That has persisted until the present day, but seems a bit odd in retrospect. All the other COMEDI drivers that use port I/O or memory regions will fail to set up the device if any region cannot be requested. It seems unlikely that the sys admin would deliberately choose a port that cannot be requested just to leave a gap in the device's usable subdevice numbers, and failing to set-up the device will provide a more noticeable indication that something hasn't been set-up correctly, so change the driver to fail to set up the device if any of the port I/O regions cannot be requested. Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Link: https://patch.msgid.link/20251028112833.15033-1-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 reStructuredText 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.