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authorXu Yilun <yilun.xu@intel.com>2021-03-08 04:59:36 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-03-28 15:58:18 +0300
commitd72260cc7879c72c186900e7c153007a6137ed8e (patch)
tree316d95232beaa8ad34a78df037b764333b089f30 /Documentation/fpga
parentbbfb54e7b3e484943f8c00c58a0d6549e9078640 (diff)
downloadlinux-d72260cc7879c72c186900e7c153007a6137ed8e.tar.xz
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>
Diffstat (limited to 'Documentation/fpga')
-rw-r--r--Documentation/fpga/dfl.rst26
1 files changed, 26 insertions, 0 deletions
diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
index c41ac76ffaae..f3a1223f2517 100644
--- a/Documentation/fpga/dfl.rst
+++ b/Documentation/fpga/dfl.rst
@@ -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