[PATCH 2/2] fpga: dfl: add the userspace I/O device support for DFL devices

[Xu Yilun <yilun.xu@intel.com>]

This patch supports the DFL drivers be written in userspace. This is
realized by exposing the userspace I/O device interfaces. The driver
leverages the uio_pdrv_genirq, it adds the uio_pdrv_genirq platform
device with the DFL device's resources, and let the generic UIO platform
device driver provide support to userspace access to kernel interrupts
and memory locations.

Signed-off-by: Xu Yilun <yilun.xu@intel.com>
---
 drivers/fpga/Kconfig        | 10 ++++++
 drivers/fpga/Makefile       |  1 +
 drivers/fpga/dfl-uio-pdev.c | 83 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+)
 create mode 100644 drivers/fpga/dfl-uio-pdev.c

diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
index 5d7f0ae..e054722 100644
--- a/drivers/fpga/Kconfig
+++ b/drivers/fpga/Kconfig
@@ -202,6 +202,16 @@ config FPGA_DFL_NIOS_INTEL_PAC_N3000
 	  the card. It also instantiates the SPI master (spi-altera) for
 	  the card's BMC (Board Management Controller).
 
+config FPGA_DFL_UIO_PDEV
+	tristate "FPGA DFL Driver for Userspace I/O platform devices"
+	depends on FPGA_DFL && UIO_PDRV_GENIRQ
+	help
+	  Enable this to allow some DFL drivers be written in userspace. It
+	  adds the uio_pdrv_genirq platform device with the DFL device's
+	  resources, and let the generic UIO platform device driver provide
+	  support to userspace access to kernel interrupts and memory
+	  locations.
+
 config FPGA_DFL_PCI
 	tristate "FPGA DFL PCIe Device Driver"
 	depends on PCI && FPGA_DFL
diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
index 18dc9885..e07b3d5 100644
--- a/drivers/fpga/Makefile
+++ b/drivers/fpga/Makefile
@@ -45,6 +45,7 @@ dfl-afu-objs := dfl-afu-main.o dfl-afu-region.o dfl-afu-dma-region.o
 dfl-afu-objs += dfl-afu-error.o
 
 obj-$(CONFIG_FPGA_DFL_NIOS_INTEL_PAC_N3000)	+= dfl-n3000-nios.o
+obj-$(CONFIG_FPGA_DFL_UIO_PDEV)	+= dfl-uio-pdev.o
 
 # Drivers for FPGAs which implement DFL
 obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o
diff --git a/drivers/fpga/dfl-uio-pdev.c b/drivers/fpga/dfl-uio-pdev.c
new file mode 100644
index 0000000..d35b846
--- /dev/null
+++ b/drivers/fpga/dfl-uio-pdev.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DFL driver for Userspace I/O platform devices
+ *
+ * Copyright (C) 2020 Intel Corporation, Inc.
+ */
+#include <linux/dfl.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/uio_driver.h>
+
+#define DRIVER_NAME "dfl-uio-pdev"
+
+static int dfl_uio_pdev_probe(struct dfl_device *ddev)
+{
+	struct device *dev = &ddev->dev;
+	struct platform_device_info pdevinfo = { 0 };
+	struct uio_info uio_pdata = { 0 };
+	struct platform_device *uio_pdev;
+	struct resource *res;
+	int i, idx = 0;
+
+	pdevinfo.name = "uio_pdrv_genirq";
+
+	res = kcalloc(ddev->num_irqs + 1, sizeof(*res), GFP_KERNEL);
+	if (!res)
+		return -ENOMEM;
+
+	res[idx].parent = &ddev->mmio_res;
+	res[idx].flags = IORESOURCE_MEM;
+	res[idx].start = ddev->mmio_res.start;
+	res[idx].end = ddev->mmio_res.end;
+	++idx;
+
+	/* then add irq resource */
+	for (i = 0; i < ddev->num_irqs; i++) {
+		res[idx].flags = IORESOURCE_IRQ;
+		res[idx].start = ddev->irqs[i];
+		res[idx].end = ddev->irqs[i];
+		++idx;
+	}
+
+	uio_pdata.name = DRIVER_NAME;
+	uio_pdata.version = "0";
+
+	pdevinfo.res = res;
+	pdevinfo.num_res = idx;
+	pdevinfo.parent = &ddev->dev;
+	pdevinfo.id = PLATFORM_DEVID_AUTO;
+	pdevinfo.data = &uio_pdata;
+	pdevinfo.size_data = sizeof(uio_pdata);
+
+	uio_pdev = platform_device_register_full(&pdevinfo);
+	if (!IS_ERR(uio_pdev))
+		dev_set_drvdata(dev, uio_pdev);
+
+	kfree(res);
+
+	return PTR_ERR_OR_ZERO(uio_pdev);
+}
+
+static void dfl_uio_pdev_remove(struct dfl_device *ddev)
+{
+	struct platform_device *uio_pdev = dev_get_drvdata(&ddev->dev);
+
+	platform_device_unregister(uio_pdev);
+}
+
+static struct dfl_driver dfl_uio_pdev_driver = {
+	.drv	= {
+		.name       = DRIVER_NAME,
+	},
+	.probe	= dfl_uio_pdev_probe,
+	.remove	= dfl_uio_pdev_remove,
+};
+module_dfl_driver(dfl_uio_pdev_driver);
+
+MODULE_DESCRIPTION("DFL driver for Userspace I/O platform devices");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4