bus: fsl-mc: add fsl-mc userspace support

Adding userspace support for the MC (Management Complex) means exporting
an ioctl capable device file representing the root resource container.

This new functionality in the fsl-mc bus driver intends to provide
userspace applications an interface to interact with the MC firmware.

Commands that are composed in userspace are sent to the MC firmware
through the FSL_MC_SEND_MC_COMMAND ioctl.  By default the implicit MC
I/O portal is used for this operation, but if the implicit one is busy,
a dynamic portal is allocated and then freed upon execution.

The command received through the ioctl interface is checked against a
known whitelist of accepted MC commands. Commands that attempt a change
in hardware configuration will need CAP_NET_ADMIN, while commands used
in debugging do not need it.
Acked-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20210114170752.2927915-4-ciorneiioana@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -180,6 +180,7 @@ Code  Seq#    Include File                                           Comments
 'R'   00-1F  linux/random.h                                          conflict!
 'R'   01     linux/rfkill.h                                          conflict!
 'R'   C0-DF  net/bluetooth/rfcomm.h
+'R'   E0     uapi/linux/fsl_mc.h
 'S'   all    linux/cdrom.h                                           conflict!
 'S'   80-81  scsi/scsi_ioctl.h                                       conflict!
 'S'   82-FF  scsi/scsi.h                                             conflict!

drivers/bus/fsl-mc/Kconfig

@@ -14,3 +14,10 @@ config FSL_MC_BUS
 	  architecture.  The fsl-mc bus driver handles discovery of
 	  DPAA2 objects (which are represented as Linux devices) and
 	  binding objects to drivers.
+
+config FSL_MC_UAPI_SUPPORT
+	bool "Management Complex (MC) userspace support"
+	depends on FSL_MC_BUS
+	help
+	  Provides userspace support for interrogating, creating, destroying or
+	  configuring DPAA2 objects exported by the Management Complex.

drivers/bus/fsl-mc/Makefile

@@ -16,3 +16,6 @@ mc-bus-driver-objs := fsl-mc-bus.o \
 		      fsl-mc-allocator.o \
 		      fsl-mc-msi.o \
 		      dpmcp.o
+
+# MC userspace support
+obj-$(CONFIG_FSL_MC_UAPI_SUPPORT) += fsl-mc-uapi.o

drivers/bus/fsl-mc/dprc-driver.c

@@ -603,6 +603,7 @@ int dprc_setup(struct fsl_mc_device *mc_dev)
 	struct irq_domain *mc_msi_domain;
 	bool mc_io_created = false;
 	bool msi_domain_set = false;
+	bool uapi_created = false;
 	u16 major_ver, minor_ver;
 	size_t region_size;
 	int error;
@@ -635,6 +636,11 @@ int dprc_setup(struct fsl_mc_device *mc_dev)
 			return error;
 
 		mc_io_created = true;
+	} else {
+		error = fsl_mc_uapi_create_device_file(mc_bus);
+		if (error < 0)
+			return -EPROBE_DEFER;
+		uapi_created = true;
 	}
 
 	mc_msi_domain = fsl_mc_find_msi_domain(&mc_dev->dev);
@@ -692,6 +698,9 @@ int dprc_setup(struct fsl_mc_device *mc_dev)
 		mc_dev->mc_io = NULL;
 	}
 
+	if (uapi_created)
+		fsl_mc_uapi_remove_device_file(mc_bus);
+
 	return error;
 }
 EXPORT_SYMBOL_GPL(dprc_setup);
@@ -763,6 +772,7 @@ static void dprc_teardown_irq(struct fsl_mc_device *mc_dev)
 
 int dprc_cleanup(struct fsl_mc_device *mc_dev)
 {
+	struct fsl_mc_bus *mc_bus = to_fsl_mc_bus(mc_dev);
 	int error;
 
 	/* this function should be called only for DPRCs, it
@@ -793,6 +803,8 @@ int dprc_cleanup(struct fsl_mc_device *mc_dev)
 	if (!fsl_mc_is_root_dprc(&mc_dev->dev)) {
 		fsl_destroy_mc_io(mc_dev->mc_io);
 		mc_dev->mc_io = NULL;
+	} else {
+		fsl_mc_uapi_remove_device_file(mc_bus);
 	}
 
 	return 0;

drivers/bus/fsl-mc/fsl-mc-private.h

@@ -10,6 +10,8 @@
 
 #include <linux/fsl/mc.h>
 #include <linux/mutex.h>
+#include <linux/ioctl.h>
+#include <linux/miscdevice.h>
 
 /*
  * Data Path Management Complex (DPMNG) General API
@@ -542,6 +544,22 @@ struct fsl_mc_resource_pool {
 	struct fsl_mc_bus *mc_bus;
 };
 
+/**
+ * struct fsl_mc_uapi - information associated with a device file
+ * @misc: struct miscdevice linked to the root dprc
+ * @device: newly created device in /dev
+ * @mutex: mutex lock to serialize the open/release operations
+ * @local_instance_in_use: local MC I/O instance in use or not
+ * @static_mc_io: pointer to the static MC I/O object
+ */
+struct fsl_mc_uapi {
+	struct miscdevice misc;
+	struct device *device;
+	struct mutex mutex; /* serialize open/release operations */
+	u32 local_instance_in_use;
+	struct fsl_mc_io *static_mc_io;
+};
+
 /**
  * struct fsl_mc_bus - logical bus that corresponds to a physical DPRC
  * @mc_dev: fsl-mc device for the bus device itself.
@@ -551,6 +569,7 @@ struct fsl_mc_resource_pool {
  * @irq_resources: Pointer to array of IRQ objects for the IRQ pool
  * @scan_mutex: Serializes bus scanning
  * @dprc_attr: DPRC attributes
+ * @uapi_misc: struct that abstracts the interaction with userspace
  */
 struct fsl_mc_bus {
 	struct fsl_mc_device mc_dev;
@@ -558,6 +577,7 @@ struct fsl_mc_bus {
 	struct fsl_mc_device_irq *irq_resources;
 	struct mutex scan_mutex;    /* serializes bus scanning */
 	struct dprc_attributes dprc_attr;
+	struct fsl_mc_uapi uapi_misc;
 };
 
 #define to_fsl_mc_bus(_mc_dev) \
@@ -614,4 +634,23 @@ struct fsl_mc_device *fsl_mc_device_lookup(struct fsl_mc_obj_desc *obj_desc,
 
 u16 mc_cmd_hdr_read_cmdid(struct fsl_mc_command *cmd);
 
+#ifdef CONFIG_FSL_MC_UAPI_SUPPORT
+
+int fsl_mc_uapi_create_device_file(struct fsl_mc_bus *mc_bus);
+
+void fsl_mc_uapi_remove_device_file(struct fsl_mc_bus *mc_bus);
+
+#else
+
+static inline int fsl_mc_uapi_create_device_file(struct fsl_mc_bus *mc_bus)
+{
+	return 0;
+}
+
+static inline void fsl_mc_uapi_remove_device_file(struct fsl_mc_bus *mc_bus)
+{
+}
+
+#endif
+
 #endif /* _FSL_MC_PRIVATE_H_ */

include/uapi/linux/fsl_mc.h

@@ -16,10 +16,19 @@
  * struct fsl_mc_command - Management Complex (MC) command structure
  * @header: MC command header
  * @params: MC command parameters
+ *
+ * Used by FSL_MC_SEND_MC_COMMAND
  */
 struct fsl_mc_command {
 	__le64 header;
 	__le64 params[MC_CMD_NUM_OF_PARAMS];
 };
 
+#define FSL_MC_SEND_CMD_IOCTL_TYPE	'R'
+#define FSL_MC_SEND_CMD_IOCTL_SEQ	0xE0
+
+#define FSL_MC_SEND_MC_COMMAND \
+	_IOWR(FSL_MC_SEND_CMD_IOCTL_TYPE, FSL_MC_SEND_CMD_IOCTL_SEQ, \
+	struct fsl_mc_command)
+
 #endif /* _UAPI_FSL_MC_H_ */