Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
To:     mchehab@kernel.org, "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
Cc:     linux-media@vger.kernel.org,
        linux-kernel-mentees@lists.linuxfoundation.o,
        linux-kernel@vger.kernel.org
Subject: [PATCH 3/3] media: vidtv: add initial debugfs interface
Date:   Thu, 24 Dec 2020 12:04:02 -0300
Message-Id: <20201224150402.1945788-3-dwlsalmeida@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Add a debugfs interface for testing purposes  that can be enabled
by selecting **DVB_VIDTV_DEBUGFS**. This makes it possible to:

dynamically inject errors at runtime by interacting with the files
at /sys/kernel/debug/vidtv/*

read some dvbv5 statistics from userspace more easily.

This is entirely optional and the driver will work without this option
selected.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 .../driver-api/media/drivers/vidtv.rst        |  80 +++---
 drivers/media/test-drivers/vidtv/Kconfig      |  13 +
 .../media/test-drivers/vidtv/vidtv_bridge.c   |  13 +
 .../media/test-drivers/vidtv/vidtv_bridge.h   |   2 +
 .../media/test-drivers/vidtv/vidtv_debugfs.h  |  42 +++
 drivers/media/test-drivers/vidtv/vidtv_mux.c  | 272 ++++++++++++++++++
 drivers/media/test-drivers/vidtv/vidtv_mux.h  |   7 +
 drivers/media/test-drivers/vidtv/vidtv_ts.c   |   8 +
 drivers/media/test-drivers/vidtv/vidtv_ts.h   |   8 +
 9 files changed, 412 insertions(+), 33 deletions(-)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_debugfs.h

diff --git a/Documentation/driver-api/media/drivers/vidtv.rst b/Documentation/driver-api/media/drivers/vidtv.rst
index 673bdff919ea..e7c450289774 100644
--- a/Documentation/driver-api/media/drivers/vidtv.rst
+++ b/Documentation/driver-api/media/drivers/vidtv.rst
@@ -227,6 +227,9 @@ vidtv_mux.[ch]
 	#. Delivering the resulting TS packets to the bridge
 	   driver so it can pass them to the demux.
 
+vidtv_debugfs.h
+	Exposes data structures used in vidtv's debugfs interface.
+
 Testing vidtv with v4l-utils
 ----------------------------
 
@@ -431,27 +434,53 @@ For more information on dvb-zap check its online documentation here:
 See also: `zap <https://www.linuxtv.org/wiki/index.php/Zap>`_.
 
 
-What can still be improved in vidtv
------------------------------------
+Vidtv *debugfs* integration
+___________________________
+
+Vidtv now comes with a *debugfs* interface that can be enabled by selecting
+**DVB_VIDTV_DEBUGFS**. Using it, one can
+
+#. dynamically inject errors at runtime by interacting with the files at /sys/kernel/debug/vidtv/*
+
+#. read some dvbv5 statistics from userspace more easily
+
+.. note::
+	This is entirely optional and the driver will work without this option selected.
+
+At boot, vidtv will set up a directory per simulated frontend. Here is a list of
+created files and their associated functionality once they are written to:
+
+noise
+	The probability of adding random noise in the packets (0 - 10000).
+drop
+	Drop n packets at random
+shl
+	Shift left n bytes at random
+shr
+	Shift right n bytes at random
+discontinuity
+	Create n discontinuities at random. This means artificially increasing
+	the continuity counters such that a discontinuity error is generated.
+
+Another option is to provide a probability of such events ocurring. Drop, shl,
+shr, and discontinuity have versions that take in a probability in the [0,
+10000] range.
 
-Add *debugfs* integration
-~~~~~~~~~~~~~~~~~~~~~~~~~
+Writing to the files at the frontend directory will target all packets in the
+mux buffer. Alternatively, vidtv will also create a directory per PID. Writing
+to these files will, in turn, only affect that particular PID.
 
-Although frontend drivers provide DVBv5 statistics via the .read_status
-call, a nice addition would be to make additional statistics available to
-userspace via debugfs, which is a simple-to-use, RAM-based filesystem
-specifically designed for debug purposes.
 
-The logic for this would be implemented on a separate file so as not to
-pollute the frontend driver.  These statistics are driver-specific and can
-be useful during tests.
+What can still be improved in vidtv
+-----------------------------------
+
+Improve debugfs support
+~~~~~~~~~~~~~~~~~~~~~~~
 
-The Siano driver is one example of a driver using
-debugfs to convey driver-specific statistics to userspace and it can be
-used as a reference.
+Vidtv offers support for dynamically injecting errors and retrieving some dvbv5
+stats via *debugfs*. This can be improved upon to add new ways of testing from
+userspace.
 
-This should be further enabled and disabled via a Kconfig
-option for convenience.
 
 Add a way to test video
 ~~~~~~~~~~~~~~~~~~~~~~~
@@ -468,23 +497,6 @@ which resides at::
 	drivers/media/common/v4l2-tpg/
 
 
-Add white noise simulation
-~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The vidtv tuner already has code to identify whether the chosen frequency
-is too far away from a table of valid frequencies. For now, this means that
-the demodulator can eventually lose the lock on the signal, since the tuner will
-report a bad signal quality.
-
-A nice addition is to simulate some noise when the signal quality is bad by:
-
-- Randomly dropping some TS packets. This will trigger a continuity error if the
-  continuity counter is updated but the packet is not passed on to the demux.
-
-- Updating the error statistics accordingly (e.g. BER, etc).
-
-- Simulating some noise in the encoded data.
-
 Functions and structs used within vidtv
 ---------------------------------------
 
@@ -511,3 +523,5 @@ Functions and structs used within vidtv
 .. kernel-doc:: drivers/media/test-drivers/vidtv/vidtv_common.c
 
 .. kernel-doc:: drivers/media/test-drivers/vidtv/vidtv_tuner.c
+
+.. kernel-doc:: drivers/media/test-drivers/vidtv/vidtv_debugfs.h
diff --git a/drivers/media/test-drivers/vidtv/Kconfig b/drivers/media/test-drivers/vidtv/Kconfig
index 22c4fd39461f..05513f1c67e1 100644
--- a/drivers/media/test-drivers/vidtv/Kconfig
+++ b/drivers/media/test-drivers/vidtv/Kconfig
@@ -8,4 +8,17 @@ config DVB_VIDTV
 	  working on userspace applications.
 
 
+	  When in doubt, say N.
+
+config DVB_VIDTV_DEBUGFS
+	bool "Enable debugfs for vidtv"
+	depends on DVB_VIDTV
+	depends on DEBUG_FS
+
+	help
+	  Choose Y to enable the vidtv debugfs interface. Currently allows for
+	  dynamically introducing errors in the generated MPEG Transport Stream
+	  for testing purposes.
+
+
 	  When in doubt, say N.
diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.c b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
index fc64d0c8492a..d5ebe680724f 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_bridge.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
@@ -10,6 +10,7 @@
  * Copyright (C) 2020 Daniel W. S. Almeida
  */
 
+#include <linux/debugfs.h>
 #include <linux/dev_printk.h>
 #include <linux/moduleparam.h>
 #include <linux/mutex.h>
@@ -172,6 +173,7 @@ static int vidtv_start_streaming(struct vidtv_dvb *dvb)
 		.transport_stream_id         = VIDTV_DEFAULT_TS_ID,
 		.network_id                  = VIDTV_DEFAULT_NETWORK_ID,
 		.network_name                = VIDTV_DEFAULT_NETWORK_NAME,
+		.debugfs_root                = dvb->debugfs_root,
 		.priv                        = dvb,
 	};
 	struct device *dev = &dvb->pdev->dev;
@@ -485,6 +487,7 @@ static int vidtv_bridge_dvb_init(struct vidtv_dvb *dvb)
 static int vidtv_bridge_probe(struct platform_device *pdev)
 {
 	struct vidtv_dvb *dvb;
+	struct dentry *debugfs_root;
 	int ret;
 
 	dvb = kzalloc(sizeof(*dvb), GFP_KERNEL);
@@ -501,6 +504,12 @@ static int vidtv_bridge_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, dvb);
 
+#ifdef CONFIG_DVB_VIDTV_DEBUGFS
+	debugfs_root = debugfs_create_dir("vidtv", NULL);
+	if (!IS_ERR(debugfs_root))
+		dvb->debugfs_root = debugfs_root;
+#endif //CONFIG_DVB_VIDTV_DEBUGFS
+
 	dev_info(&pdev->dev, "Successfully initialized vidtv!\n");
 	return ret;
 
@@ -516,6 +525,10 @@ static int vidtv_bridge_remove(struct platform_device *pdev)
 
 	dvb = platform_get_drvdata(pdev);
 
+#ifdef CONFIG_DVB_VIDTV_DEBUGFS
+	debugfs_remove_recursive(dvb->debugfs_root);
+#endif //CONFIG_DVB_VIDTV_DEBUGFS
+
 	mutex_destroy(&dvb->feed_lock);
 
 	for (i = 0; i < NUM_FE; ++i) {
diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.h b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
index 2528adaee27d..9ef37d8ad2cc 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_bridge.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
@@ -42,6 +42,7 @@
  * @feed_lock: Protects access to the start/stop stream logic/data.
  * @streaming: Whether we are streaming now.
  * @mux: The abstraction responsible for delivering MPEG TS packets to the bridge.
+ * @debugfs_root: A handle to vidtv's debugfs directory
  */
 struct vidtv_dvb {
 	struct platform_device *pdev;
@@ -60,6 +61,7 @@ struct vidtv_dvb {
 	bool streaming;
 
 	struct vidtv_mux *mux;
+	struct dentry *debugfs_root;
 };
 
 #endif // VIDTV_BRIDG_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_debugfs.h b/drivers/media/test-drivers/vidtv/vidtv_debugfs.h
new file mode 100644
index 000000000000..1743fe6d96cf
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_debugfs.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * Copyright (C) 2020 Daniel W. S. Almeida
+ */
+
+#ifndef VIDTV_DEBUGFS_H
+#define VIDTV_DEBUGFS_H
+#include <linux/debugfs.h>
+
+/**
+ * struct vidtv_debugfs - Represents the vidtv debugfs interface
+ *
+ * @dir_dentry: A handle to the debugfs dentry
+ * @noise: Probability of adding noise to a byte in a packet [0, 10000]
+ * @drop: Drop n packets at random.
+ * @drop_probability: Probability to randomly drop a packet [0, 10000]
+ * @shl_probability: Probability to randomly shift left a byte in a packet [0, 10000]
+ * @shr_probability: Probability to randomly shift right a byte in a packet [0, 10000]
+ * @discontinuity_probability: Probability of artificially creating a
+ * discontinuity error [0, 10000]
+ * @shl: Shift n bytes left at random, i.e. byte[i] = byte[i] << 1;
+ * @shr: Shift n bytes right at random, i.e. byte[i] = byte[i] >>1;
+ * @discontinuity: Create n discontinuity errors
+ */
+struct vidtv_debugfs {
+	struct dentry *dir_dentry;
+	u32 noise;
+	u32 drop_probability;
+	u32 shl_probability;
+	u32 shr_probability;
+	u32 discontinuity_probability;
+	u32 drop;
+	u32 shl;
+	u32 shr;
+	u32 discontinuity;
+};
+
+#endif //VIDTV_DEBUGFS_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_mux.c b/drivers/media/test-drivers/vidtv/vidtv_mux.c
index b51e6a3b8cbe..e6d69fe01908 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_mux.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_mux.c
@@ -12,11 +12,14 @@
  * Copyright (C) 2020 Daniel W. S. Almeida
  */
 
+#include "vidtv_debugfs.h"
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/dev_printk.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/math64.h>
+#include <linux/random.h>
 #include <linux/ratelimit.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -385,6 +388,204 @@ static void vidtv_mux_clear(struct vidtv_mux *m)
 	m->mux_buf_offset = 0;
 }
 
+static void vidtv_mux_add_random_noise(struct vidtv_mux *m, u32 noise_prob, u32 pkt_start)
+{
+	u8 noise;
+	u8 *pkt = m->mux_buf + pkt_start;
+	u32 i;
+
+	for (i = 0; i < TS_PACKET_LEN; i++)
+		if (prandom_u32_max(10000) < noise_prob) {
+			noise = prandom_u32_max(0xff);
+			pkt[i] = pkt[i] + noise;
+		}
+}
+
+static void vidtv_mux_drop_random(struct vidtv_mux *m, u32 drop_prob, u32 pkt_start, u32 *nbytes)
+{
+	u8 *pkt = m->mux_buf + pkt_start;
+	u8 *last_pkt = m->mux_buf + m->mux_buf_offset - TS_PACKET_LEN;
+	u32 npkts = m->mux_buf_offset / 188;
+
+	if (!npkts)
+		return;
+
+	if (prandom_u32_max(10000) < drop_prob) {
+		if (npkts > 1 && pkt != last_pkt) {
+			//overwrite victim with last packet
+			memcpy(pkt, last_pkt, TS_PACKET_LEN);
+			//remove last packet from buffer
+			memset(last_pkt, 0, TS_PACKET_LEN);
+		} else {
+			//just erase it
+			memset(pkt, 0, TS_PACKET_LEN);
+		}
+
+		//keep track of the loss of this packet
+		m->mux_buf_offset -= TS_PACKET_LEN;
+		*nbytes -= TS_PACKET_LEN;
+	}
+}
+
+static void vidtv_mux_shl_random(struct vidtv_mux *m, u32 shl_prob, u32 pkt_start)
+{
+	u8 *pkt = m->mux_buf + pkt_start;
+	/* select one of the 188 bytes at random */
+	u8 *byte = pkt + prandom_u32_max(TS_PACKET_LEN);
+
+	if (prandom_u32_max(10000) < shl_prob)
+		*byte = *byte << 1;
+}
+
+static void vidtv_mux_shr_random(struct vidtv_mux *m, u32 shr_prob, u32 pkt_start)
+{
+	u8 *pkt = m->mux_buf + pkt_start;
+	/* select one of the 188 bytes at random */
+	u8 *byte = pkt + prandom_u32_max(TS_PACKET_LEN);
+
+	if (prandom_u32_max(10000) < shr_prob)
+		*byte = *byte >> 1;
+}
+
+static void vidtv_mux_discontinuity_random(struct vidtv_mux *m, u32 disc_prob, u16 pid)
+{
+	struct vidtv_mux_pid_ctx *ctx = vidtv_mux_get_pid_ctx(m, pid);
+
+	/* if the pkt was previously corrupted such that we cannot retrieve its pid context
+	 * anymore, then bail
+	 */
+	if (!ctx)
+		return;
+
+	if (prandom_u32_max(10000) < disc_prob)
+		vidtv_ts_inc_cc(&ctx->cc);
+}
+
+static u32 vidtv_mux_get_random_pkt_offset(struct vidtv_mux *m)
+{
+	u32 npkts = m->mux_buf_offset / TS_PACKET_LEN;
+	u32 pkt_offset = prandom_u32_max(npkts) * TS_PACKET_LEN;
+
+	return pkt_offset;
+}
+
+static u32 vidtv_mux_get_random_pkt_offset_for_pid(struct vidtv_mux *m, u16 pid, bool *found)
+{
+	u32 npkts_total = m->mux_buf_offset / TS_PACKET_LEN;
+	u8 *buf = kcalloc(npkts_total, sizeof(u32), GFP_KERNEL);
+	u32 npkt = 0;
+	u32 pkt_offset = 0;
+	u32 offset;
+	u16 pkt_pid;
+
+	for (offset = 0; offset < m->mux_buf_offset; offset += TS_PACKET_LEN) {
+		pkt_pid = vidtv_ts_get_pid(&m->mux_buf[offset]);
+		if (pkt_pid == pid) {
+			buf[npkt] = offset;
+			npkt++;
+		}
+	}
+
+	*found = (npkt != 0);
+	pkt_offset = buf[prandom_u32_max(npkt)];
+	kfree(buf);
+	return pkt_offset;
+}
+
+static void vidtv_mux_handle_debugfs_input(struct vidtv_mux *m, u32 *nbytes)
+{
+	struct vidtv_mux_pid_ctx *ctx;
+	u32 pkt_offset;
+	u16 pid;
+	int bkt;
+	bool found;
+	u32 offset;
+
+#ifndef CONFIG_DVB_VIDTV_DEBUGFS
+	return;
+#endif //CONFIG_DVB_VIDTV_DEBUGFS
+
+	if (m->mux_buf_offset == 0)
+		return;
+
+	while (m->debugfs.discontinuity > 0) {
+		pkt_offset = vidtv_mux_get_random_pkt_offset(m);
+		pid = vidtv_ts_get_pid(&m->mux_buf[pkt_offset]);
+		vidtv_mux_discontinuity_random(m, 10000, pid);
+		m->debugfs.discontinuity--;
+	}
+
+	while (m->debugfs.drop > 0) {
+		pkt_offset = vidtv_mux_get_random_pkt_offset(m);
+		vidtv_mux_drop_random(m, 10000, pkt_offset, nbytes);
+		m->debugfs.drop--;
+	}
+
+	while (m->debugfs.shl > 0) {
+		pkt_offset = vidtv_mux_get_random_pkt_offset(m);
+		vidtv_mux_shl_random(m, 10000, pkt_offset);
+		m->debugfs.shl--;
+	}
+
+	while (m->debugfs.shr > 0) {
+		pkt_offset = vidtv_mux_get_random_pkt_offset(m);
+		vidtv_mux_shr_random(m, 10000, pkt_offset);
+		m->debugfs.shr--;
+	}
+
+	for (offset = 0; offset < m->mux_buf_offset; offset += TS_PACKET_LEN) {
+		pid = vidtv_ts_get_pid(&m->mux_buf[offset]);
+		vidtv_mux_discontinuity_random(m, m->debugfs.discontinuity_probability, pid);
+		vidtv_mux_add_random_noise(m, m->debugfs.noise, offset);
+		vidtv_mux_drop_random(m, m->debugfs.drop_probability, offset, nbytes);
+		vidtv_mux_shl_random(m, m->debugfs.shl_probability, offset);
+		vidtv_mux_shr_random(m, m->debugfs.shr_probability, offset);
+	}
+
+	hash_for_each(m->pid_ctx, bkt, ctx, h) {
+		while (ctx->debugfs.discontinuity > 0) {
+			pkt_offset = vidtv_mux_get_random_pkt_offset_for_pid(m, ctx->pid, &found);
+			vidtv_mux_discontinuity_random(m, 10000, ctx->pid);
+			ctx->debugfs.discontinuity--;
+		}
+
+		while (ctx->debugfs.drop > 0) {
+			pkt_offset = vidtv_mux_get_random_pkt_offset_for_pid(m, ctx->pid, &found);
+			if (found)
+				vidtv_mux_drop_random(m, 10000, pkt_offset, nbytes);
+			ctx->debugfs.drop--;
+		}
+
+		while (ctx->debugfs.shl > 0) {
+			pkt_offset = vidtv_mux_get_random_pkt_offset_for_pid(m, ctx->pid, &found);
+			if (found)
+				vidtv_mux_shl_random(m, 10000, pkt_offset);
+			ctx->debugfs.shl--;
+		}
+
+		while (ctx->debugfs.shr > 0) {
+			pkt_offset = vidtv_mux_get_random_pkt_offset_for_pid(m, ctx->pid, &found);
+			if (found)
+				vidtv_mux_shr_random(m, 10000, pkt_offset);
+			ctx->debugfs.shr--;
+		}
+
+		for (offset = 0; offset < m->mux_buf_offset; offset += TS_PACKET_LEN) {
+			pid = vidtv_ts_get_pid(&m->mux_buf[offset]);
+			if (ctx->pid == pid) {
+				vidtv_mux_discontinuity_random(m,
+							       m->debugfs.discontinuity_probability,
+							       pid);
+				vidtv_mux_add_random_noise(m, ctx->debugfs.noise, offset);
+				vidtv_mux_drop_random(m, ctx->debugfs.drop_probability,
+						      offset, nbytes);
+				vidtv_mux_shl_random(m, ctx->debugfs.shl_probability, offset);
+				vidtv_mux_shr_random(m, ctx->debugfs.shr_probability, offset);
+			}
+		}
+	}
+}
+
 #define ERR_RATE 10000000
 static void vidtv_mux_tick(struct work_struct *work)
 {
@@ -410,6 +611,7 @@ static void vidtv_mux_tick(struct work_struct *work)
 		nbytes += vidtv_mux_poll_encoders(m);
 		nbytes += vidtv_mux_pad_with_nulls(m, 256);
 
+		vidtv_mux_handle_debugfs_input(m, &nbytes);
 		npkts = nbytes / TS_PACKET_LEN;
 
 		/* if the buffer is not aligned there is a bug somewhere */
@@ -474,6 +676,71 @@ void vidtv_mux_stop_thread(struct vidtv_mux *m)
 	}
 }
 
+static void vidtv_mux_debugfs_init(struct vidtv_mux *m, struct dentry *parent)
+{
+	struct dentry *frontend_dir;
+	struct dentry *pid_dir;
+	struct vidtv_mux_pid_ctx *ctx;
+	int bkt;
+	char name[16];
+	struct dtv_frontend_properties *c;
+
+#ifndef CONFIG_DVB_VIDTV_DEBUGFS
+	return;
+#endif //CONFIG_DVB_VIDTV_DEBUGFS
+
+	c = &m->fe->dtv_property_cache;
+	//Change this if vidtv ever supports simulating more than one frontend
+	frontend_dir = debugfs_create_dir("frontend0", parent);
+	if (IS_ERR(frontend_dir))
+		return;
+
+	debugfs_create_u64("pre_bit_count", 0444, frontend_dir, &c->pre_bit_count.stat[0].uvalue);
+	debugfs_create_u64("post_bit_count", 0444, frontend_dir, &c->post_bit_count.stat[0].uvalue);
+	debugfs_create_u64("block_count", 0444, frontend_dir, &c->block_count.stat[0].uvalue);
+
+	/* these work at random for any PID in this mux */
+	debugfs_create_u32("noise", 0644, frontend_dir, &m->debugfs.noise);
+	debugfs_create_u32("drop_probability", 0644, frontend_dir, &m->debugfs.drop_probability);
+	debugfs_create_u32("shl_probability", 0644, frontend_dir, &m->debugfs.shl_probability);
+	debugfs_create_u32("shr_probability", 0644, frontend_dir, &m->debugfs.shr_probability);
+	debugfs_create_u32("discontinuity_probability", 0644, frontend_dir,
+			   &m->debugfs.discontinuity_probability);
+	debugfs_create_u32("drop", 0644, frontend_dir, &m->debugfs.drop);
+	debugfs_create_u32("shl", 0644, frontend_dir, &m->debugfs.shl);
+	debugfs_create_u32("shr", 0644, frontend_dir, &m->debugfs.shr);
+	debugfs_create_u32("discontinuity", 0644, frontend_dir, &m->debugfs.discontinuity);
+
+	hash_for_each(m->pid_ctx, bkt, ctx, h) {
+		memset(name, 0, ARRAY_SIZE(name));
+		snprintf(name, ARRAY_SIZE(name), "PID_%d", ctx->pid);
+
+		pid_dir = debugfs_create_dir(name, frontend_dir);
+		if (IS_ERR(pid_dir))
+			return;
+
+		/* these will affect the chosen PID only */
+		debugfs_create_u32("noise", 0644, pid_dir, &ctx->debugfs.noise);
+		debugfs_create_u32("drop_probability", 0644, pid_dir,
+				   &ctx->debugfs.drop_probability);
+		debugfs_create_u32("shl_probability", 0644, pid_dir,
+				   &ctx->debugfs.shl_probability);
+		debugfs_create_u32("shr_probability", 0644, pid_dir,
+				   &ctx->debugfs.shr_probability);
+		debugfs_create_u32("discontinuity_probability", 0644, pid_dir,
+				   &ctx->debugfs.discontinuity_probability);
+		debugfs_create_u32("drop", 0644, pid_dir, &ctx->debugfs.drop);
+		debugfs_create_u32("shl", 0644, pid_dir, &ctx->debugfs.shl);
+		debugfs_create_u32("shr", 0644, pid_dir, &ctx->debugfs.shr);
+		debugfs_create_u32("discontinuity", 0644, pid_dir,
+				   &ctx->debugfs.discontinuity);
+
+		ctx->debugfs.dir_dentry = pid_dir;
+	}
+
+	m->debugfs.dir_dentry = frontend_dir;
+}
+
 struct vidtv_mux *vidtv_mux_init(struct dvb_frontend *fe,
 				 struct device *dev,
 				 struct vidtv_mux_init_args *args)
@@ -521,6 +788,8 @@ struct vidtv_mux *vidtv_mux_init(struct dvb_frontend *fe,
 	if (vidtv_mux_pid_ctx_init(m) < 0)
 		goto free_channel_si;
 
+	vidtv_mux_debugfs_init(m, args->debugfs_root);
+
 	return m;
 
 free_channel_si:
@@ -542,5 +811,8 @@ void vidtv_mux_destroy(struct vidtv_mux *m)
 	vidtv_channels_destroy(m);
 	kfree(m->network_name);
 	vfree(m->mux_buf);
+#ifdef CONFIG_DVB_VIDTV_DEBUGFS
+	debugfs_remove_recursive(m->debugfs.dir_dentry);
+#endif //CONFIG_DVB_VIDTV_DEBUGFS
 	kfree(m);
 }
diff --git a/drivers/media/test-drivers/vidtv/vidtv_mux.h b/drivers/media/test-drivers/vidtv/vidtv_mux.h
index ad82eb72b841..b6ca9f330afd 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_mux.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_mux.h
@@ -22,6 +22,7 @@
 #include <media/dvb_frontend.h>
 
 #include "vidtv_psi.h"
+#include "vidtv_debugfs.h"
 
 /**
  * struct vidtv_mux_timing - Timing related information
@@ -77,11 +78,13 @@ struct vidtv_mux_si {
  * @cc: The continuity counter for this PID. It is incremented on every TS
  * pack and it will wrap around at 0xf0. If the decoder notices a sudden jump in
  * this counter this will trigger a discontinuity state.
+ * @debugfs: debugfs interface for this mpeg pid
  * @h: This is embedded in a hash table, mapping pid -> vidtv_mux_pid_ctx
  */
 struct vidtv_mux_pid_ctx {
 	u16 pid;
 	u8 cc; /* continuity counter */
+	struct vidtv_debugfs debugfs;
 	struct hlist_node h;
 };
 
@@ -108,6 +111,7 @@ struct vidtv_mux_pid_ctx {
  * @transport_stream_id: The transport stream ID
  * @network_id: The network ID
  * @network_name: The network name
+ * @debugfs: The debugfs interface for the whole mux, if any.
  * @priv: Private data.
  */
 struct vidtv_mux {
@@ -139,6 +143,7 @@ struct vidtv_mux {
 	u16 transport_stream_id;
 	u16 network_id;
 	char *network_name;
+	struct vidtv_debugfs debugfs;
 	void *priv;
 };
 
@@ -155,6 +160,7 @@ struct vidtv_mux {
  * @channels: an optional list of channels to use
  * @network_id: The network ID
  * @network_name: The network name
+ * @debugfs_root: the debugfs root directory, if any
  * @priv: Private data.
  */
 struct vidtv_mux_init_args {
@@ -168,6 +174,7 @@ struct vidtv_mux_init_args {
 	struct vidtv_channel *channels;
 	u16 network_id;
 	char *network_name;
+	struct dentry *debugfs_root;
 	void *priv;
 };
 
diff --git a/drivers/media/test-drivers/vidtv/vidtv_ts.c b/drivers/media/test-drivers/vidtv/vidtv_ts.c
index ca4bb9c40b78..dca6fa8afa57 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_ts.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_ts.c
@@ -134,3 +134,11 @@ u32 vidtv_ts_pcr_write_into(struct pcr_write_args args)
 
 	return nbytes;
 }
+
+u16 vidtv_ts_get_pid(u8 *pkt)
+{
+	struct vidtv_mpeg_ts *ts_pkt = (struct vidtv_mpeg_ts *)pkt;
+	u16 bitfield = be16_to_cpu(ts_pkt->bitfield);
+	u16 ret = bitfield & GENMASK(12, 0);
+	return ret;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_ts.h b/drivers/media/test-drivers/vidtv/vidtv_ts.h
index 09b4ffd02829..f19824021966 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_ts.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_ts.h
@@ -103,4 +103,12 @@ u32 vidtv_ts_null_write_into(struct null_packet_write_args args);
  */
 u32 vidtv_ts_pcr_write_into(struct pcr_write_args args);
 
+/**
+ * vidtv_ts_get_pid - Extract the MPEG PID value out of a mpeg ts packet
+ * @pkt: pointer to packet
+ *
+ * Return: The mpeg ts pid in cpu endianness
+ */
+u16 vidtv_ts_get_pid(u8 *pkt);
+
 #endif //VIDTV_TS_H
-- 
2.29.2