[PATCH V4 XRT Alveo 06/20] fpga: xrt: char dev node helper functions

[Lizhi Hou]

Helper functions for char device node creation / removal for platform
drivers. This is part of platform driver infrastructure.

Signed-off-by: Sonal Santan <sonal.santan@xxxxxxxxxx>
Signed-off-by: Max Zhen <max.zhen@xxxxxxxxxx>
Signed-off-by: Lizhi Hou <lizhi.hou@xxxxxxxxxx>
---
 drivers/fpga/xrt/lib/cdev.c | 232 ++++++++++++++++++++++++++++++++++++
 1 file changed, 232 insertions(+)
 create mode 100644 drivers/fpga/xrt/lib/cdev.c

diff --git a/drivers/fpga/xrt/lib/cdev.c b/drivers/fpga/xrt/lib/cdev.c
new file mode 100644
index 000000000000..38efd24b6e10
--- /dev/null
+++ b/drivers/fpga/xrt/lib/cdev.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xilinx Alveo FPGA device node helper functions.
+ *
+ * Copyright (C) 2020-2021 Xilinx, Inc.
+ *
+ * Authors:
+ *	Cheng Zhen <maxz@xxxxxxxxxx>
+ */
+
+#include "xleaf.h"
+
+extern struct class *xrt_class;
+
+#define XRT_CDEV_DIR		"xfpga"
+#define INODE2PDATA(inode)	\
+	container_of((inode)->i_cdev, struct xrt_subdev_platdata, xsp_cdev)
+#define INODE2PDEV(inode)	\
+	to_platform_device(kobj_to_dev((inode)->i_cdev->kobj.parent))
+#define CDEV_NAME(sysdev)	(strchr((sysdev)->kobj.name, '!') + 1)
+
+/* Allow it to be accessed from cdev. */
+static void xleaf_devnode_allowed(struct platform_device *pdev)
+{
+	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
+
+	/* Allow new opens. */
+	mutex_lock(&pdata->xsp_devnode_lock);
+	pdata->xsp_devnode_online = true;
+	mutex_unlock(&pdata->xsp_devnode_lock);
+}
+
+/* Turn off access from cdev and wait for all existing user to go away. */
+static int xleaf_devnode_disallowed(struct platform_device *pdev)
+{
+	int ret = 0;
+	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
+
+	mutex_lock(&pdata->xsp_devnode_lock);
+
+	/* Prevent new opens. */
+	pdata->xsp_devnode_online = false;
+	/* Wait for existing user to close. */
+	while (!ret && pdata->xsp_devnode_ref) {
+		int rc;
+
+		mutex_unlock(&pdata->xsp_devnode_lock);
+		rc = wait_for_completion_killable(&pdata->xsp_devnode_comp);
+		mutex_lock(&pdata->xsp_devnode_lock);
+
+		if (rc == -ERESTARTSYS) {
+			/* Restore online state. */
+			pdata->xsp_devnode_online = true;
+			xrt_err(pdev, "%s is in use, ref=%d",
+				CDEV_NAME(pdata->xsp_sysdev),
+				pdata->xsp_devnode_ref);
+			ret = -EBUSY;
+		}
+	}
+
+	mutex_unlock(&pdata->xsp_devnode_lock);
+
+	return ret;
+}
+
+static struct platform_device *
+__xleaf_devnode_open(struct inode *inode, bool excl)
+{
+	struct xrt_subdev_platdata *pdata = INODE2PDATA(inode);
+	struct platform_device *pdev = INODE2PDEV(inode);
+	bool opened = false;
+
+	mutex_lock(&pdata->xsp_devnode_lock);
+
+	if (pdata->xsp_devnode_online) {
+		if (excl && pdata->xsp_devnode_ref) {
+			xrt_err(pdev, "%s has already been opened exclusively",
+				CDEV_NAME(pdata->xsp_sysdev));
+		} else if (!excl && pdata->xsp_devnode_excl) {
+			xrt_err(pdev, "%s has been opened exclusively",
+				CDEV_NAME(pdata->xsp_sysdev));
+		} else {
+			pdata->xsp_devnode_ref++;
+			pdata->xsp_devnode_excl = excl;
+			opened = true;
+			xrt_info(pdev, "opened %s, ref=%d",
+				 CDEV_NAME(pdata->xsp_sysdev),
+				 pdata->xsp_devnode_ref);
+		}
+	} else {
+		xrt_err(pdev, "%s is offline", CDEV_NAME(pdata->xsp_sysdev));
+	}
+
+	mutex_unlock(&pdata->xsp_devnode_lock);
+
+	pdev = opened ? pdev : NULL;
+	return pdev;
+}
+
+struct platform_device *
+xleaf_devnode_open_excl(struct inode *inode)
+{
+	return __xleaf_devnode_open(inode, true);
+}
+
+struct platform_device *
+xleaf_devnode_open(struct inode *inode)
+{
+	return __xleaf_devnode_open(inode, false);
+}
+EXPORT_SYMBOL_GPL(xleaf_devnode_open);
+
+void xleaf_devnode_close(struct inode *inode)
+{
+	struct xrt_subdev_platdata *pdata = INODE2PDATA(inode);
+	struct platform_device *pdev = INODE2PDEV(inode);
+	bool notify = false;
+
+	mutex_lock(&pdata->xsp_devnode_lock);
+
+	WARN_ON(pdata->xsp_devnode_ref == 0);
+	pdata->xsp_devnode_ref--;
+	if (pdata->xsp_devnode_ref == 0) {
+		pdata->xsp_devnode_excl = false;
+		notify = true;
+	}
+	if (notify) {
+		xrt_info(pdev, "closed %s, ref=%d",
+			 CDEV_NAME(pdata->xsp_sysdev), pdata->xsp_devnode_ref);
+	} else {
+		xrt_info(pdev, "closed %s, notifying waiter",
+			 CDEV_NAME(pdata->xsp_sysdev));
+	}
+
+	mutex_unlock(&pdata->xsp_devnode_lock);
+
+	if (notify)
+		complete(&pdata->xsp_devnode_comp);
+}
+EXPORT_SYMBOL_GPL(xleaf_devnode_close);
+
+static inline enum xrt_subdev_file_mode
+devnode_mode(struct xrt_subdev_drvdata *drvdata)
+{
+	return drvdata->xsd_file_ops.xsf_mode;
+}
+
+int xleaf_devnode_create(struct platform_device *pdev, const char *file_name,
+			 const char *inst_name)
+{
+	struct xrt_subdev_drvdata *drvdata = DEV_DRVDATA(pdev);
+	struct xrt_subdev_file_ops *fops = &drvdata->xsd_file_ops;
+	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
+	struct cdev *cdevp;
+	struct device *sysdev;
+	int ret = 0;
+	char fname[256];
+
+	mutex_init(&pdata->xsp_devnode_lock);
+	init_completion(&pdata->xsp_devnode_comp);
+
+	cdevp = &DEV_PDATA(pdev)->xsp_cdev;
+	cdev_init(cdevp, &fops->xsf_ops);
+	cdevp->owner = fops->xsf_ops.owner;
+	cdevp->dev = MKDEV(MAJOR(fops->xsf_dev_t), pdev->id);
+
+	/*
+	 * Set pdev as parent of cdev so that when pdev (and its platform
+	 * data) will not be freed when cdev is not freed.
+	 */
+	cdev_set_parent(cdevp, &DEV(pdev)->kobj);
+
+	ret = cdev_add(cdevp, cdevp->dev, 1);
+	if (ret) {
+		xrt_err(pdev, "failed to add cdev: %d", ret);
+		goto failed;
+	}
+	if (!file_name)
+		file_name = pdev->name;
+	if (!inst_name) {
+		if (devnode_mode(drvdata) == XRT_SUBDEV_FILE_MULTI_INST) {
+			snprintf(fname, sizeof(fname), "%s/%s/%s.%u",
+				 XRT_CDEV_DIR, DEV_PDATA(pdev)->xsp_root_name,
+				 file_name, pdev->id);
+		} else {
+			snprintf(fname, sizeof(fname), "%s/%s/%s",
+				 XRT_CDEV_DIR, DEV_PDATA(pdev)->xsp_root_name,
+				 file_name);
+		}
+	} else {
+		snprintf(fname, sizeof(fname), "%s/%s/%s.%s", XRT_CDEV_DIR,
+			 DEV_PDATA(pdev)->xsp_root_name, file_name, inst_name);
+	}
+	sysdev = device_create(xrt_class, NULL, cdevp->dev, NULL, "%s", fname);
+	if (IS_ERR(sysdev)) {
+		ret = PTR_ERR(sysdev);
+		xrt_err(pdev, "failed to create device node: %d", ret);
+		goto failed_cdev_add;
+	}
+	pdata->xsp_sysdev = sysdev;
+
+	xleaf_devnode_allowed(pdev);
+
+	xrt_info(pdev, "created (%d, %d): /dev/%s",
+		 MAJOR(cdevp->dev), pdev->id, fname);
+	return 0;
+
+failed_cdev_add:
+	cdev_del(cdevp);
+failed:
+	cdevp->owner = NULL;
+	return ret;
+}
+
+int xleaf_devnode_destroy(struct platform_device *pdev)
+{
+	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
+	struct cdev *cdevp = &pdata->xsp_cdev;
+	dev_t dev = cdevp->dev;
+	int rc;
+
+	rc = xleaf_devnode_disallowed(pdev);
+	if (rc)
+		return rc;
+
+	xrt_info(pdev, "removed (%d, %d): /dev/%s/%s", MAJOR(dev), MINOR(dev),
+		 XRT_CDEV_DIR, CDEV_NAME(pdata->xsp_sysdev));
+	device_destroy(xrt_class, cdevp->dev);
+	pdata->xsp_sysdev = NULL;
+	cdev_del(cdevp);
+	return 0;
+}
-- 
2.27.0