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Subject[PATCH v6 2/2] Documentation: fpga: dfl: Add description for DFL UIO support
This patch adds description for UIO support for dfl devices on DFL

Signed-off-by: Xu Yilun <>
v2: no doc in v1, add it for v2.
v3: some documentation fixes.
v4: documentation change since the driver matching is changed.
v5: no change.
v6: improve the title of the userspace driver support section.
some word improvement.
Documentation/fpga/dfl.rst | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
index 0404fe6..c33b6d0 100644
--- a/Documentation/fpga/dfl.rst
+++ b/Documentation/fpga/dfl.rst
@@ -7,6 +7,7 @@ Authors:
- Enno Luebbers <>
- Xiao Guangrong <>
- Wu Hao <>
+- Xu Yilun <>

The Device Feature List (DFL) FPGA framework (and drivers according to
this framework) hides the very details of low layer hardwares and provides
@@ -502,6 +503,29 @@ FME Partial Reconfiguration Sub Feature driver (see drivers/fpga/dfl-fme-pr.c)
could be a reference.

+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 get a DFL device in their system. In some cases users may need a userspace
+driver for the DFL device:
+* Users may need to run some diagnostic test for their hardwares.
+* 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 dfl-uio-pdev module exposes the UIO device interfaces for this
+purpose. It adds the uio_pdrv_genirq platform device with the resources of
+the DFL feature, and lets the generic UIO platform device driver provide UIO
+support to userspace.
+FPGA_DFL_UIO_PDEV should be selected to enable the dfl-uio-pdev module driver.
+To support a new DFL feature been directly accessed via UIO, 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
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