cfbad64706
The EtherAVB device requires the SKB data to be aligned to 128 bytes. The alignment is done by allocating an skb 128 bytes larger than the maximum frame size supported by the device and adjusting the headroom to fit the requirement. This code has been refactored a few times and small issues have been added along the way. The issues are not harmful but prevent merging parts of the Rx code which have been split in two implementations with the addition of RZ/G2L support, a device that supports larger frame sizes. This change removes the need for duplicated and somewhat inaccurate hardware alignment constrains stored in the hardware information struct by creating a helper to handle the allocation of an skb and alignment of an skb data. For the R-Car class of devices the maximum frame size is 4K and each descriptor is limited to 2K of data. The current implementation does not support split descriptors, this limits the frame size to 2K. The current hardware information however records the descriptor size just under 2K due to bad understanding of the device when larger MTUs where added. For the RZ/G2L device the maximum frame size is 8K and each descriptor is limited to 4K of data. The current hardware information records this correctly, but it gets the alignment constrains wrong as just aligns it by 128, it does not extend it by 128 bytes to allow the full frame to be stored. This works because the RZ/G2L device supports split descriptors and allocates each skb to 8K and aligns each 4K descriptor in this space. Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Reviewed-by: Paul Barker <paul.barker.ct@bp.renesas.com> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru> Signed-off-by: David S. Miller <davem@davemloft.net>
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.