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When using dma_map_sg() to map the scatterlist with iommu enabled, the entries in the scatterlist can be mergerd into less but longer entries in the function __finalise_sg(). So that the number of valid mapped entries is actually smaller than ureq->num_reqs,and there are still some invalid entries in the scatterlist with dma_addr=0xffffffff and len=0. Writing these invalid sg entries into the dma_desc can cause a data transmission error. The function dma_map_sg() returns the number of valid map entries and the return value is assigned to usb_request::num_mapped_sgs in function usb_gadget_map_request_by_dev(). So that just write valid mapped entries into dma_desc according to the usb_request::num_mapped_sgs, and set the IOC bit if it's the last valid mapped entry. This patch poses no risk to no-iommu situation, cause ureq->num_mapped_sgs equals ureq->num_sgs while using dma_direct_map_sg() to map the scatterlist whith iommu disabled. Signed-off-by: Peng Hongchi <hongchi.peng@siengine.com> Link: https://lore.kernel.org/r/20240523100315.7226-1-hongchi.peng@siengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| README | ||
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.