Merge branch 'wwan-debugfs-tweaks'

Sergey Ryazanov says:

====================
WWAN debugfs tweaks

This is a follow-up series to just applied IOSM (and WWAN) debugfs
interface support [1]. The series has two main goals:
1. move the driver-specific debugfs knobs to a subdirectory;
2. make the debugfs interface optional for both IOSM and for the WWAN
   core.

As for the first part, I must say that it was my mistake. I suggested to
place debugfs entries under a common per WWAN device directory. But I
missed the driver subdirectory in the example, so it become:

/sys/kernel/debugfs/wwan/wwan0/trace

Since the traces collection is a driver-specific feature, it is better
to keep it under the driver-specific subdirectory:

/sys/kernel/debugfs/wwan/wwan0/iosm/trace

It is desirable to be able to entirely disable the debugfs interface. It
can be disabled for several reasons, including security and consumed
storage space. See detailed rationale with usage example in the 4th
patch.

The changes themselves are relatively simple, but require a code
rearrangement. So to make changes clear, I chose to split them into
preparatory and main changes and properly describe each of them.

IOSM part is compile-tested only since I do not have IOSM supported
device, so it needs Ack from the driver developers.

I would like to thank Johannes Berg and Leon Romanovsky. Their
suggestions and comments helped a lot to rework the initial
over-engineered solution to something less confusing and much more
simple. Thanks!

1. https://lore.kernel.org/netdev/20211120162155.1216081-1-m.chetan.kumar@linux.intel.com
2. https://patchwork.kernel.org/project/netdevbpf/patch/20211204174033.950528-1-arnd@kernel.org/
====================

Link: https://lore.kernel.org/r/20211207092140.19142-1-ryazanov.s.a@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

12 files changed, 134 insertions, 41 deletions

diff --git a/drivers/net/wwan/Kconfig b/drivers/net/wwan/Kconfig
index 9f5111a77da9..609fd4a2c865 100644
--- a/drivers/net/wwan/Kconfig
+++ b/drivers/net/wwan/Kconfig
@@ -16,6 +16,17 @@ config WWAN
 
 if WWAN
 
+config WWAN_DEBUGFS
+	bool "WWAN devices debugfs interface" if EXPERT
+	depends on DEBUG_FS
+	default y
+	help
+	  Enables debugfs infrastructure for the WWAN core and device drivers.
+
+	  If this option is selected, then you can find the debug interface
+	  elements for each WWAN device in a directory that is corresponding to
+	  the device name: debugfs/wwan/wwanX.
+
 config WWAN_HWSIM
 	tristate "Simulated WWAN device"
 	help
@@ -85,7 +96,7 @@ config IOSM
 	tristate "IOSM Driver for Intel M.2 WWAN Device"
 	depends on INTEL_IOMMU
 	select NET_DEVLINK
-	select RELAY
+	select RELAY if WWAN_DEBUGFS
 	help
 	  This driver enables Intel M.2 WWAN Device communication.
 
diff --git a/drivers/net/wwan/iosm/Makefile b/drivers/net/wwan/iosm/Makefile
index 5c2528beca2a..fa8d6afd18e1 100644
--- a/drivers/net/wwan/iosm/Makefile
+++ b/drivers/net/wwan/iosm/Makefile
@@ -21,7 +21,10 @@ iosm-y = \
 	iosm_ipc_mux_codec.o		\
 	iosm_ipc_devlink.o		\
 	iosm_ipc_flash.o		\
-	iosm_ipc_coredump.o		\
+	iosm_ipc_coredump.o
+
+iosm-$(CONFIG_WWAN_DEBUGFS) += \
+	iosm_ipc_debugfs.o		\
 	iosm_ipc_trace.o
 
 obj-$(CONFIG_IOSM) := iosm.o
diff --git a/drivers/net/wwan/iosm/iosm_ipc_debugfs.c b/drivers/net/wwan/iosm/iosm_ipc_debugfs.c
new file mode 100644
index 000000000000..f2f57751a7d2
--- /dev/null
+++ b/drivers/net/wwan/iosm/iosm_ipc_debugfs.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020-2021 Intel Corporation.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/wwan.h>
+
+#include "iosm_ipc_imem.h"
+#include "iosm_ipc_trace.h"
+#include "iosm_ipc_debugfs.h"
+
+void ipc_debugfs_init(struct iosm_imem *ipc_imem)
+{
+	struct dentry *debugfs_pdev = wwan_get_debugfs_dir(ipc_imem->dev);
+
+	ipc_imem->debugfs_dir = debugfs_create_dir(KBUILD_MODNAME,
+						   debugfs_pdev);
+
+	ipc_imem->trace = ipc_trace_init(ipc_imem);
+	if (!ipc_imem->trace)
+		dev_warn(ipc_imem->dev, "trace channel init failed");
+}
+
+void ipc_debugfs_deinit(struct iosm_imem *ipc_imem)
+{
+	ipc_trace_deinit(ipc_imem->trace);
+	debugfs_remove_recursive(ipc_imem->debugfs_dir);
+}
diff --git a/drivers/net/wwan/iosm/iosm_ipc_debugfs.h b/drivers/net/wwan/iosm/iosm_ipc_debugfs.h
new file mode 100644
index 000000000000..8a84bfa2c14a
--- /dev/null
+++ b/drivers/net/wwan/iosm/iosm_ipc_debugfs.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only
+ *
+ * Copyright (C) 2020-2021 Intel Corporation.
+ */
+
+#ifndef IOSM_IPC_DEBUGFS_H
+#define IOSM_IPC_DEBUGFS_H
+
+#ifdef CONFIG_WWAN_DEBUGFS
+void ipc_debugfs_init(struct iosm_imem *ipc_imem);
+void ipc_debugfs_deinit(struct iosm_imem *ipc_imem);
+#else
+static inline void ipc_debugfs_init(struct iosm_imem *ipc_imem) {}
+static inline void ipc_debugfs_deinit(struct iosm_imem *ipc_imem) {}
+#endif
+
+#endif
diff --git a/drivers/net/wwan/iosm/iosm_ipc_imem.c b/drivers/net/wwan/iosm/iosm_ipc_imem.c
index 1be07114c85d..2a6ddd7c6c88 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_imem.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_imem.c
@@ -11,6 +11,7 @@
 #include "iosm_ipc_imem.h"
 #include "iosm_ipc_port.h"
 #include "iosm_ipc_trace.h"
+#include "iosm_ipc_debugfs.h"
 
 /* Check the wwan ips if it is valid with Channel as input. */
 static int ipc_imem_check_wwan_ips(struct ipc_mem_channel *chnl)
@@ -272,8 +273,8 @@ static void ipc_imem_dl_skb_process(struct iosm_imem *ipc_imem,
 		if (port_id == IPC_MEM_CTRL_CHL_ID_7)
 			ipc_imem_sys_devlink_notify_rx(ipc_imem->ipc_devlink,
 						       skb);
-		else if (port_id == ipc_imem->trace->chl_id)
-			ipc_trace_port_rx(ipc_imem->trace, skb);
+		else if (ipc_is_trace_channel(ipc_imem, port_id))
+			ipc_trace_port_rx(ipc_imem, skb);
 		else
 			wwan_port_rx(ipc_imem->ipc_port[port_id]->iosm_port,
 				     skb);
@@ -554,11 +555,7 @@ static void ipc_imem_run_state_worker(struct work_struct *instance)
 		ctrl_chl_idx++;
 	}
 
-	ipc_imem->trace = ipc_imem_trace_channel_init(ipc_imem);
-	if (!ipc_imem->trace) {
-		dev_err(ipc_imem->dev, "trace channel init failed");
-		return;
-	}
+	ipc_debugfs_init(ipc_imem);
 
 	ipc_task_queue_send_task(ipc_imem, ipc_imem_send_mdm_rdy_cb, 0, NULL, 0,
 				 false);
@@ -1175,7 +1172,7 @@ void ipc_imem_cleanup(struct iosm_imem *ipc_imem)
 
 	if (test_and_clear_bit(FULLY_FUNCTIONAL, &ipc_imem->flag)) {
 		ipc_mux_deinit(ipc_imem->mux);
-		ipc_trace_deinit(ipc_imem->trace);
+		ipc_debugfs_deinit(ipc_imem);
 		ipc_wwan_deinit(ipc_imem->wwan);
 		ipc_port_deinit(ipc_imem->ipc_port);
 	}
diff --git a/drivers/net/wwan/iosm/iosm_ipc_imem.h b/drivers/net/wwan/iosm/iosm_ipc_imem.h
index cec38009c44a..86a1ffe61729 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_imem.h
+++ b/drivers/net/wwan/iosm/iosm_ipc_imem.h
@@ -341,6 +341,7 @@ enum ipc_phase {
  * @ev_mux_net_transmit_pending:0 means inform the IPC tasklet to pass
  * @reset_det_n:		Reset detect flag
  * @pcie_wake_n:		Pcie wake flag
+ * @debugfs_dir:		Debug FS directory for driver-specific entries
  */
 struct iosm_imem {
 	struct iosm_mmio *mmio;
@@ -350,7 +351,9 @@ struct iosm_imem {
 	struct iosm_mux *mux;
 	struct iosm_cdev *ipc_port[IPC_MEM_MAX_CHANNELS];
 	struct iosm_pcie *pcie;
+#ifdef CONFIG_WWAN_DEBUGFS
 	struct iosm_trace *trace;
+#endif
 	struct device *dev;
 	enum ipc_mem_device_ipc_state ipc_requested_state;
 	struct ipc_mem_channel channels[IPC_MEM_MAX_CHANNELS];
@@ -380,6 +383,9 @@ struct iosm_imem {
 	   ev_mux_net_transmit_pending:1,
 	   reset_det_n:1,
 	   pcie_wake_n:1;
+#ifdef CONFIG_WWAN_DEBUGFS
+	struct dentry *debugfs_dir;
+#endif
 };
 
 /**
diff --git a/drivers/net/wwan/iosm/iosm_ipc_imem_ops.c b/drivers/net/wwan/iosm/iosm_ipc_imem_ops.c
index 43f1796a8984..d2072a84ab08 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_imem_ops.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_imem_ops.c
@@ -11,7 +11,6 @@
 #include "iosm_ipc_imem_ops.h"
 #include "iosm_ipc_port.h"
 #include "iosm_ipc_task_queue.h"
-#include "iosm_ipc_trace.h"
 
 /* Open a packet data online channel between the network layer and CP. */
 int ipc_imem_sys_wwan_open(struct iosm_imem *ipc_imem, int if_id)
@@ -108,23 +107,6 @@ void ipc_imem_wwan_channel_init(struct iosm_imem *ipc_imem,
 			"failed to register the ipc_wwan interfaces");
 }
 
-/**
- * ipc_imem_trace_channel_init - Initializes trace channel.
- * @ipc_imem:          Pointer to iosm_imem struct.
- *
- * Returns: Pointer to trace instance on success else NULL
- */
-struct iosm_trace *ipc_imem_trace_channel_init(struct iosm_imem *ipc_imem)
-{
-	struct ipc_chnl_cfg chnl_cfg = { 0 };
-
-	ipc_chnl_cfg_get(&chnl_cfg, IPC_MEM_CTRL_CHL_ID_3);
-	ipc_imem_channel_init(ipc_imem, IPC_CTYPE_CTRL, chnl_cfg,
-			      IRQ_MOD_OFF);
-
-	return ipc_trace_init(ipc_imem);
-}
-
 /* Map SKB to DMA for transfer */
 static int ipc_imem_map_skb_to_dma(struct iosm_imem *ipc_imem,
 				   struct sk_buff *skb)
diff --git a/drivers/net/wwan/iosm/iosm_ipc_imem_ops.h b/drivers/net/wwan/iosm/iosm_ipc_imem_ops.h
index e36ee2782629..f8afb217d9e2 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_imem_ops.h
+++ b/drivers/net/wwan/iosm/iosm_ipc_imem_ops.h
@@ -141,5 +141,5 @@ int ipc_imem_sys_devlink_read(struct iosm_devlink *ipc_devlink, u8 *data,
  */
 int ipc_imem_sys_devlink_write(struct iosm_devlink *ipc_devlink,
 			       unsigned char *buf, int count);
-struct iosm_trace *ipc_imem_trace_channel_init(struct iosm_imem *ipc_imem);
+
 #endif
diff --git a/drivers/net/wwan/iosm/iosm_ipc_trace.c b/drivers/net/wwan/iosm/iosm_ipc_trace.c
index c5fa12599c2b..eeecfa3d10c5 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_trace.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_trace.c
@@ -17,11 +17,13 @@
 
 /**
  * ipc_trace_port_rx - Receive trace packet from cp and write to relay buffer
- * @ipc_trace:  Pointer to the ipc trace data-struct
+ * @ipc_imem:   Pointer to iosm_imem structure
  * @skb:        Pointer to struct sk_buff
  */
-void ipc_trace_port_rx(struct iosm_trace *ipc_trace, struct sk_buff *skb)
+void ipc_trace_port_rx(struct iosm_imem *ipc_imem, struct sk_buff *skb)
 {
+	struct iosm_trace *ipc_trace = ipc_imem->trace;
+
 	if (ipc_trace->ipc_rchan)
 		relay_write(ipc_trace->ipc_rchan, skb->data, skb->len);
 
@@ -132,9 +134,14 @@ static const struct file_operations ipc_trace_fops = {
  */
 struct iosm_trace *ipc_trace_init(struct iosm_imem *ipc_imem)
 {
-	struct iosm_trace *ipc_trace = kzalloc(sizeof(*ipc_trace), GFP_KERNEL);
-	struct dentry *debugfs_pdev;
+	struct ipc_chnl_cfg chnl_cfg = { 0 };
+	struct iosm_trace *ipc_trace;
+
+	ipc_chnl_cfg_get(&chnl_cfg, IPC_MEM_CTRL_CHL_ID_3);
+	ipc_imem_channel_init(ipc_imem, IPC_CTYPE_CTRL, chnl_cfg,
+			      IRQ_MOD_OFF);
 
+	ipc_trace = kzalloc(sizeof(*ipc_trace), GFP_KERNEL);
 	if (!ipc_trace)
 		return NULL;
 
@@ -144,15 +151,14 @@ struct iosm_trace *ipc_trace_init(struct iosm_imem *ipc_imem)
 	ipc_trace->chl_id = IPC_MEM_CTRL_CHL_ID_3;
 
 	mutex_init(&ipc_trace->trc_mutex);
-	debugfs_pdev = wwan_get_debugfs_dir(ipc_imem->dev);
 
 	ipc_trace->ctrl_file = debugfs_create_file(IOSM_TRC_DEBUGFS_TRACE_CTRL,
 						   IOSM_TRC_FILE_PERM,
-						   debugfs_pdev,
+						   ipc_imem->debugfs_dir,
 						   ipc_trace, &ipc_trace_fops);
 
 	ipc_trace->ipc_rchan = relay_open(IOSM_TRC_DEBUGFS_TRACE,
-					  debugfs_pdev,
+					  ipc_imem->debugfs_dir,
 					  IOSM_TRC_SUB_BUFF_SIZE,
 					  IOSM_TRC_N_SUB_BUFF,
 					  &relay_callbacks, NULL);
@@ -166,6 +172,9 @@ struct iosm_trace *ipc_trace_init(struct iosm_imem *ipc_imem)
  */
 void ipc_trace_deinit(struct iosm_trace *ipc_trace)
 {
+	if (!ipc_trace)
+		return;
+
 	debugfs_remove(ipc_trace->ctrl_file);
 	relay_close(ipc_trace->ipc_rchan);
 	mutex_destroy(&ipc_trace->trc_mutex);
diff --git a/drivers/net/wwan/iosm/iosm_ipc_trace.h b/drivers/net/wwan/iosm/iosm_ipc_trace.h
index 53346183af9c..5ebe7790585c 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_trace.h
+++ b/drivers/net/wwan/iosm/iosm_ipc_trace.h
@@ -45,7 +45,30 @@ struct iosm_trace {
 	enum trace_ctrl_mode mode;
 };
 
+#ifdef CONFIG_WWAN_DEBUGFS
+
+static inline bool ipc_is_trace_channel(struct iosm_imem *ipc_mem, u16 chl_id)
+{
+	return ipc_mem->trace && ipc_mem->trace->chl_id == chl_id;
+}
+
 struct iosm_trace *ipc_trace_init(struct iosm_imem *ipc_imem);
 void ipc_trace_deinit(struct iosm_trace *ipc_trace);
-void ipc_trace_port_rx(struct iosm_trace *ipc_trace, struct sk_buff *skb);
+void ipc_trace_port_rx(struct iosm_imem *ipc_imem, struct sk_buff *skb);
+
+#else
+
+static inline bool ipc_is_trace_channel(struct iosm_imem *ipc_mem, u16 chl_id)
+{
+	return false;
+}
+
+static inline void ipc_trace_port_rx(struct iosm_imem *ipc_imem,
+				     struct sk_buff *skb)
+{
+	dev_kfree_skb(skb);
+}
+
+#endif
+
 #endif
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 5bf62dc35ac7..1508dc2a497b 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -50,7 +50,9 @@ struct wwan_device {
 	atomic_t port_id;
 	const struct wwan_ops *ops;
 	void *ops_ctxt;
+#ifdef CONFIG_WWAN_DEBUGFS
 	struct dentry *debugfs_dir;
+#endif
 };
 
 /**
@@ -146,6 +148,7 @@ static struct wwan_device *wwan_dev_get_by_name(const char *name)
 	return to_wwan_dev(dev);
 }
 
+#ifdef CONFIG_WWAN_DEBUGFS
 struct dentry *wwan_get_debugfs_dir(struct device *parent)
 {
 	struct wwan_device *wwandev;
@@ -157,6 +160,7 @@ struct dentry *wwan_get_debugfs_dir(struct device *parent)
 	return wwandev->debugfs_dir;
 }
 EXPORT_SYMBOL_GPL(wwan_get_debugfs_dir);
+#endif
 
 /* This function allocates and registers a new WWAN device OR if a WWAN device
  * already exist for the given parent, it gets a reference and return it.
@@ -166,7 +170,6 @@ EXPORT_SYMBOL_GPL(wwan_get_debugfs_dir);
 static struct wwan_device *wwan_create_dev(struct device *parent)
 {
 	struct wwan_device *wwandev;
-	const char *wwandev_name;
 	int err, id;
 
 	/* The 'find-alloc-register' operation must be protected against
@@ -206,9 +209,11 @@ static struct wwan_device *wwan_create_dev(struct device *parent)
 		goto done_unlock;
 	}
 
-	wwandev_name = kobject_name(&wwandev->dev.kobj);
-	wwandev->debugfs_dir = debugfs_create_dir(wwandev_name,
-						  wwan_debugfs_dir);
+#ifdef CONFIG_WWAN_DEBUGFS
+	wwandev->debugfs_dir =
+			debugfs_create_dir(kobject_name(&wwandev->dev.kobj),
+					   wwan_debugfs_dir);
+#endif
 
 done_unlock:
 	mutex_unlock(&wwan_register_lock);
@@ -240,7 +245,9 @@ static void wwan_remove_dev(struct wwan_device *wwandev)
 		ret = device_for_each_child(&wwandev->dev, NULL, is_wwan_child);
 
 	if (!ret) {
+#ifdef CONFIG_WWAN_DEBUGFS
 		debugfs_remove_recursive(wwandev->debugfs_dir);
+#endif
 		device_unregister(&wwandev->dev);
 	} else {
 		put_device(&wwandev->dev);
@@ -1140,7 +1147,9 @@ static int __init wwan_init(void)
 		goto destroy;
 	}
 
+#ifdef CONFIG_WWAN_DEBUGFS
 	wwan_debugfs_dir = debugfs_create_dir("wwan", NULL);
+#endif
 
 	return 0;
 
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
index 1646aa3e6779..e143c88bf4b0 100644
--- a/include/linux/wwan.h
+++ b/include/linux/wwan.h
@@ -171,6 +171,13 @@ int wwan_register_ops(struct device *parent, const struct wwan_ops *ops,
 
 void wwan_unregister_ops(struct device *parent);
 
+#ifdef CONFIG_WWAN_DEBUGFS
 struct dentry *wwan_get_debugfs_dir(struct device *parent);
+#else
+static inline struct dentry *wwan_get_debugfs_dir(struct device *parent)
+{
+	return ERR_PTR(-ENODEV);
+}
+#endif
 
 #endif /* __WWAN_H */