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Documentation: fpga: dfl: Add description for DFL UIO support 

This patch adds description for UIO support for dfl devices on DFL
bus.

Reviewed-by: Tom Rix <trix@redhat.com>
Reviewed-by: Wu Hao <hao.wu@intel.com>
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/1615168776-8553-3-git-send-email-yilun.xu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xu Yilun 2021-03-08 09:59:36 +08:00 committed by Greg Kroah-Hartman
parent bbfb54e7b3
commit d72260cc78
1 changed files with 26 additions and 0 deletions
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26
Documentation/fpga/dfl.rst
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@ -7,6 +7,7 @@ Authors:
- Enno Luebbers <enno.luebbers@intel.com>
- Xiao Guangrong <guangrong.xiao@linux.intel.com>
- Wu Hao <hao.wu@intel.com>
- Xu Yilun <yilun.xu@intel.com>
The Device Feature List (DFL) FPGA framework (and drivers according to
this framework) hides the very details of low layer hardwares and provides
@ -530,6 +531,31 @@ Being able to specify more than one DFL per BAR has been considered, but it
was determined the use case did not provide value. Specifying a single DFL
per BAR simplifies the implementation and allows for extra error checking.
Userspace driver support for DFL devices
========================================
The purpose of an FPGA is to be reprogrammed with newly developed hardware
components. New hardware can instantiate a new private feature in the DFL, and
then present a DFL device in the system. In some cases users may need a
userspace driver for the DFL device:
* Users may need to run some diagnostic test for their hardware.
* Users may prototype the kernel driver in user space.
* Some hardware is designed for specific purposes and does not fit into one of
the standard kernel subsystems.
This requires direct access to MMIO space and interrupt handling from
userspace. The uio_dfl module exposes the UIO device interfaces for this
purpose.
Currently the uio_dfl driver only supports the Ether Group sub feature, which
has no irq in hardware. So the interrupt handling is not added in this driver.
UIO_DFL should be selected to enable the uio_dfl module driver. To support a
new DFL feature via UIO direct access, its feature id should be added to the
driver's id_table.
Open discussion
===============
FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration