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The value of the "resource_alignment" can be specified using a kernel
command-line argument ("pci=resource_alignment=") or through the
corresponding sysfs attribute under the /sys/bus/pci path.
Previously, when the value was set via the kernel command-line argument,
and then subsequently accessed through sysfs attribute, the value read back
was not correct:
# grep -oE 'pci=resource_alignment.+' /proc/cmdline
pci=resource_alignment=20@00:1f.2
# cat /sys/bus/pci/resource_alignment
20@00:1f.
This was also true when the value was set through the sysfs attribute
without including a trailing newline:
# echo -n 20@00:1f.2 > /sys/bus/pci/resource_alignment
# cat /sys/bus/pci/resource_alignment
20@00:1f.
When it was set through the sysfs attribute *including* a newline,
reading it back worked as intended:
# echo 20@00:1f.2 > /sys/bus/pci/resource_alignment
# cat /sys/bus/pci/resource_alignment
20@00:1f.2
To fix this inconsistency, append a trailing newline in the show() function
and strip the trailing line in the store() function if one is present.
Also, allow for the value previously set using either a command-line
argument or through the sysfs object to be cleared at run-time.
[bhelgaas: fold in kfree fix from
https://lore.kernel.org/linux-pci/20210604133230.983956-4-kw@linux.com]
Fixes: e499081da1 ("PCI: Force trailing new line to resource_alignment_param in sysfs")
Link: https://lore.kernel.org/r/20210603000112.703037-4-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.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.