[PATCH v6 07/29] fpga: dfl: add chardev support for feature devices

[Wu Hao]

For feature devices drivers, both the FPGA Management Engine (FME) and
Accelerated Function Unit (AFU) driver need to expose user interfaces via
the device file, for example, mmap and ioctls.

This patch adds chardev support in the dfl driver for feature devices,
FME and AFU. It reserves the chardev regions for FME and AFU, and provide
interfaces for FME and AFU driver to register their device file operations.

Signed-off-by: Tim Whisonant <tim.whisonant@xxxxxxxxx>
Signed-off-by: Enno Luebbers <enno.luebbers@xxxxxxxxx>
Signed-off-by: Shiva Rao <shiva.rao@xxxxxxxxx>
Signed-off-by: Christopher Rauer <christopher.rauer@xxxxxxxxx>
Signed-off-by: Zhang Yi <yi.z.zhang@xxxxxxxxx>
Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
---
v2: rebased
v3: move chardev support to fpga-dfl framework
v4: rebase, and add more comments in code.
v5: rebase, and add dfl_ prefix to APIs and data structures.
v6: add index in dfl_devs to link to dfl_chrdevs.
    improve naming on APIs.
---
 drivers/fpga/dfl.c | 125 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 drivers/fpga/dfl.h |   8 ++++
 2 files changed, 130 insertions(+), 3 deletions(-)

diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index 24bc83f..702b3ce 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -22,6 +22,11 @@
  * dfl_devs table which is indexed by dfl_id_type, e.g name string used for
  * platform device creation (define name strings in dfl.h, as they could be
  * reused by platform device drivers).
+ *
+ * if the new feature dev needs chardev support, then it's required to add
+ * a new item in dfl_chardevs table, and configure dfl_devs[i].devt_type as
+ * index to dfl_chardevs table. If no chardev support just set devt_type
+ * as one invalid index (DFL_FPGA_DEVT_MAX).
  */
 enum dfl_id_type {
 	FME_ID,		/* fme id allocation and mapping */
@@ -29,22 +34,48 @@ enum dfl_id_type {
 	DFL_ID_MAX,
 };
 
+enum dfl_fpga_devt_type {
+	DFL_FPGA_DEVT_FME,
+	DFL_FPGA_DEVT_PORT,
+	DFL_FPGA_DEVT_MAX,
+};
+
 /**
  * dfl_dev_info - dfl feature device information.
  * @name: name string of the feature platform device.
  * @dfh_id: id value in Device Feature Header (DFH) register by DFL spec.
  * @id: idr id of the feature dev.
+ * @devt_type: index to dfl_chrdevs[].
  */
 struct dfl_dev_info {
 	const char *name;
 	u32 dfh_id;
 	struct idr id;
+	enum dfl_fpga_devt_type devt_type;
 };
 
 /* it is indexed by dfl_id_type */
 static struct dfl_dev_info dfl_devs[] = {
-	{.name = DFL_FPGA_FEATURE_DEV_FME, .dfh_id = DFH_ID_FIU_FME},
-	{.name = DFL_FPGA_FEATURE_DEV_PORT, .dfh_id = DFH_ID_FIU_PORT},
+	{.name = DFL_FPGA_FEATURE_DEV_FME, .dfh_id = DFH_ID_FIU_FME,
+	 .devt_type = DFL_FPGA_DEVT_FME},
+	{.name = DFL_FPGA_FEATURE_DEV_PORT, .dfh_id = DFH_ID_FIU_PORT,
+	 .devt_type = DFL_FPGA_DEVT_PORT},
+};
+
+/**
+ * dfl_chardev_info - chardev information of dfl feature device
+ * @name: nmae string of the char device.
+ * @devt: devt of the char device.
+ */
+struct dfl_chardev_info {
+	const char *name;
+	dev_t devt;
+};
+
+/* indexed by enum dfl_fpga_devt_type */
+struct dfl_chardev_info dfl_chrdevs[] = {
+	{.name = DFL_FPGA_FEATURE_DEV_FME},
+	{.name = DFL_FPGA_FEATURE_DEV_PORT},
 };
 
 static void dfl_ids_init(void)
@@ -105,6 +136,86 @@ static enum dfl_id_type dfh_id_to_type(u32 id)
 	return DFL_ID_MAX;
 }
 
+static void dfl_chardev_uinit(void)
+{
+	int i;
+
+	for (i = 0; i < DFL_FPGA_DEVT_MAX; i++)
+		if (MAJOR(dfl_chrdevs[i].devt)) {
+			unregister_chrdev_region(dfl_chrdevs[i].devt,
+						 MINORMASK);
+			dfl_chrdevs[i].devt = MKDEV(0, 0);
+		}
+}
+
+static int dfl_chardev_init(void)
+{
+	int i, ret;
+
+	for (i = 0; i < DFL_FPGA_DEVT_MAX; i++) {
+		ret = alloc_chrdev_region(&dfl_chrdevs[i].devt, 0, MINORMASK,
+					  dfl_chrdevs[i].name);
+		if (ret)
+			goto exit;
+	}
+
+	return 0;
+
+exit:
+	dfl_chardev_uinit();
+	return ret;
+}
+
+static dev_t dfl_get_devt(enum dfl_fpga_devt_type type, int id)
+{
+	if (type >= DFL_FPGA_DEVT_MAX)
+		return 0;
+
+	return MKDEV(MAJOR(dfl_chrdevs[type].devt), id);
+}
+
+/**
+ * dfl_fpga_dev_ops_register - register cdev ops for feature dev
+ *
+ * @pdev: feature dev.
+ * @fops: file operations for feature dev's cdev.
+ * @owner: owning module/driver.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int dfl_fpga_dev_ops_register(struct platform_device *pdev,
+			      const struct file_operations *fops,
+			      struct module *owner)
+{
+	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
+
+	cdev_init(&pdata->cdev, fops);
+	pdata->cdev.owner = owner;
+
+	/*
+	 * set parent to the feature device so that its refcount is
+	 * decreased after the last refcount of cdev is gone, that
+	 * makes sure the feature device is valid during device
+	 * file's life-cycle.
+	 */
+	pdata->cdev.kobj.parent = &pdev->dev.kobj;
+
+	return cdev_add(&pdata->cdev, pdev->dev.devt, 1);
+}
+EXPORT_SYMBOL_GPL(dfl_fpga_dev_ops_register);
+
+/**
+ * dfl_fpga_dev_ops_unregister - unregister cdev ops for feature dev
+ * @pdev: feature dev.
+ */
+void dfl_fpga_dev_ops_unregister(struct platform_device *pdev)
+{
+	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
+
+	cdev_del(&pdata->cdev);
+}
+EXPORT_SYMBOL_GPL(dfl_fpga_dev_ops_unregister);
+
 /**
  * struct build_feature_devs_info - info collected during feature dev build.
  *
@@ -266,6 +377,7 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
 		return fdev->id;
 
 	fdev->dev.parent = &binfo->cdev->region->dev;
+	fdev->dev.devt = dfl_get_devt(dfl_devs[type].devt_type, fdev->id);
 
 	return 0;
 }
@@ -703,13 +815,20 @@ void dfl_fpga_feature_devs_remove(struct dfl_fpga_cdev *cdev)
 
 static int __init dfl_fpga_init(void)
 {
+	int ret;
+
 	dfl_ids_init();
 
-	return 0;
+	ret = dfl_chardev_init();
+	if (ret)
+		dfl_ids_destroy();
+
+	return ret;
 }
 
 static void __exit dfl_fpga_exit(void)
 {
+	dfl_chardev_uinit();
 	dfl_ids_destroy();
 }
 
diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
index 47ecb3b..66c2ade 100644
--- a/drivers/fpga/dfl.h
+++ b/drivers/fpga/dfl.h
@@ -15,6 +15,7 @@
 #define __FPGA_DFL_H
 
 #include <linux/bitfield.h>
+#include <linux/cdev.h>
 #include <linux/delay.h>
 #include <linux/fs.h>
 #include <linux/iopoll.h>
@@ -150,6 +151,7 @@ struct dfl_feature {
  *
  * @node: node to link feature devs to container device's port_dev_list.
  * @lock: mutex to protect platform data.
+ * @cdev: cdev of feature dev.
  * @dev: ptr to platform device linked with this platform data.
  * @dfl_cdev: ptr to container device.
  * @disable_count: count for port disable.
@@ -159,6 +161,7 @@ struct dfl_feature {
 struct dfl_feature_platform_data {
 	struct list_head node;
 	struct mutex lock;
+	struct cdev cdev;
 	struct platform_device *dev;
 	struct dfl_fpga_cdev *dfl_cdev;
 	unsigned int disable_count;
@@ -176,6 +179,11 @@ static inline int dfl_feature_platform_data_size(const int num)
 		num * sizeof(struct dfl_feature);
 }
 
+int dfl_fpga_dev_ops_register(struct platform_device *pdev,
+			      const struct file_operations *fops,
+			      struct module *owner);
+void dfl_fpga_dev_ops_unregister(struct platform_device *pdev);
+
 #define dfl_fpga_dev_for_each_feature(pdata, feature)			    \
 	for ((feature) = (pdata)->features;				    \
 	   (feature) < (pdata)->features + (pdata)->num; (feature)++)
-- 
1.8.3.1