uio: uio_dfl: add userspace i/o driver for DFL bus

This patch supports the DFL drivers be written in userspace. This is
realized by exposing the userspace I/O device interfaces.

The driver now only binds the ether group feature, which has no irq. So
the irq support is not implemented yet.

Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Reviewed-by: Tom Rix <trix@redhat.com>

Author: yilunxu1984

MAINTAINERS

@@ -6895,6 +6895,7 @@ S:	Maintained
 F:	Documentation/ABI/testing/sysfs-bus-dfl*
 F:	Documentation/fpga/dfl.rst
 F:	drivers/fpga/dfl*
+F:	drivers/uio/uio_dfl.c
 F:	include/linux/dfl.h
 F:	include/uapi/linux/fpga-dfl.h
 

drivers/uio/Kconfig

@@ -165,4 +165,21 @@ config UIO_HV_GENERIC
 	  to network and storage devices from userspace.
 
 	  If you compile this as a module, it will be called uio_hv_generic.
+
+config UIO_DFL
+	tristate "Generic driver for DFL (Device Feature List) bus"
+	depends on FPGA_DFL
+	help
+	  Generic DFL (Device Feature List) driver for Userspace I/O devices.
+	  It is useful to provide direct access to DFL devices from userspace.
+	  A sample userspace application using this driver is available for
+	  download in a git repository:
+
+	    git clone https://github.com/OPAE/opae-sdk.git
+
+	  It could be found at:
+
+	    opae-sdk/tools/libopaeuio/
+
+	  If you compile this as a module, it will be called uio_dfl.
 endif

drivers/uio/Makefile

@@ -11,3 +11,4 @@ obj-$(CONFIG_UIO_PRUSS)         += uio_pruss.o
 obj-$(CONFIG_UIO_MF624)         += uio_mf624.o
 obj-$(CONFIG_UIO_FSL_ELBC_GPCM)	+= uio_fsl_elbc_gpcm.o
 obj-$(CONFIG_UIO_HV_GENERIC)	+= uio_hv_generic.o
+obj-$(CONFIG_UIO_DFL)	+= uio_dfl.o

drivers/uio/uio_dfl.c

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic DFL driver for Userspace I/O devicess
+ *
+ * Copyright (C) 2021 Intel Corporation, Inc.
+ */
+#include <linux/dfl.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/uio_driver.h>
+
+#define DRIVER_NAME "uio_dfl"
+
+static int uio_dfl_probe(struct dfl_device *ddev)
+{
+	struct resource *r = &ddev->mmio_res;
+	struct device *dev = &ddev->dev;
+	struct uio_info *uioinfo;
+	struct uio_mem *uiomem;
+	int ret;
+
+	uioinfo = devm_kzalloc(dev, sizeof(struct uio_info), GFP_KERNEL);
+	if (!uioinfo)
+		return -ENOMEM;
+
+	uioinfo->name = DRIVER_NAME;
+	uioinfo->version = "0";
+
+	uiomem = &uioinfo->mem[0];
+	uiomem->memtype = UIO_MEM_PHYS;
+	uiomem->addr = r->start & PAGE_MASK;
+	uiomem->offs = r->start & ~PAGE_MASK;
+	uiomem->size = (uiomem->offs + resource_size(r)
+			+ PAGE_SIZE - 1) & PAGE_MASK;
+	uiomem->name = r->name;
+
+	/* Irq is yet to be supported */
+	uioinfo->irq = UIO_IRQ_NONE;
+
+	ret = devm_uio_register_device(dev, uioinfo);
+	if (ret)
+		dev_err(dev, "unable to register uio device\n");
+
+	return ret;
+}
+
+#define FME_FEATURE_ID_ETH_GROUP	0x10
+
+static const struct dfl_device_id uio_dfl_ids[] = {
+	{ FME_ID, FME_FEATURE_ID_ETH_GROUP },
+	{ }
+};
+MODULE_DEVICE_TABLE(dfl, uio_dfl_ids);
+
+static struct dfl_driver uio_dfl_driver = {
+	.drv = {
+		.name = DRIVER_NAME,
+	},
+	.id_table	= uio_dfl_ids,
+	.probe		= uio_dfl_probe,
+};
+module_dfl_driver(uio_dfl_driver);
+
+MODULE_DESCRIPTION("Generic DFL driver for Userspace I/O devices");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");