media: visl: add virtual stateless decoder driver

A virtual stateless device for stateless uAPI development purposes.

This tool's objective is to help the development and testing of
userspace applications that use the V4L2 stateless API to decode media.

A userspace implementation can use visl to run a decoding loop even when
no hardware is available or when the kernel uAPI for the codec has not
been upstreamed yet. This can reveal bugs at an early stage.

This driver can also trace the contents of the V4L2 controls submitted
to it.  It can also dump the contents of the vb2 buffers through a
debugfs interface. This is in many ways similar to the tracing
infrastructure available for other popular encode/decode APIs out there
and can help develop a userspace application by using another (working)
one as a reference.

Note that no actual decoding of video frames is performed by visl. The
V4L2 test pattern generator is used to write various debug information
to the capture buffers instead.

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

22 files changed, 3827 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/v4l-drivers.rst b/Documentation/admin-guide/media/v4l-drivers.rst
index 9c7ebe2ca3bd..90a026ee05c6 100644
--- a/Documentation/admin-guide/media/v4l-drivers.rst
+++ b/Documentation/admin-guide/media/v4l-drivers.rst
@@ -31,4 +31,5 @@ Video4Linux (V4L) driver-specific documentation
 	si4713
 	si476x
 	vimc
+	visl
 	vivid
diff --git a/Documentation/admin-guide/media/visl.rst b/Documentation/admin-guide/media/visl.rst
new file mode 100644
index 000000000000..7d2dc78341c9
--- /dev/null
+++ b/Documentation/admin-guide/media/visl.rst
@@ -0,0 +1,175 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+The Virtual Stateless Decoder Driver (visl)
+===========================================
+
+A virtual stateless decoder device for stateless uAPI development
+purposes.
+
+This tool's objective is to help the development and testing of
+userspace applications that use the V4L2 stateless API to decode media.
+
+A userspace implementation can use visl to run a decoding loop even when
+no hardware is available or when the kernel uAPI for the codec has not
+been upstreamed yet. This can reveal bugs at an early stage.
+
+This driver can also trace the contents of the V4L2 controls submitted
+to it.  It can also dump the contents of the vb2 buffers through a
+debugfs interface. This is in many ways similar to the tracing
+infrastructure available for other popular encode/decode APIs out there
+and can help develop a userspace application by using another (working)
+one as a reference.
+
+.. note::
+
+        No actual decoding of video frames is performed by visl. The
+        V4L2 test pattern generator is used to write various debug information
+        to the capture buffers instead.
+
+Module parameters
+-----------------
+
+- visl_debug: Activates debug info, printing various debug messages through
+  dprintk. Also controls whether per-frame debug info is shown. Defaults to off.
+  Note that enabling this feature can result in slow performance through serial.
+
+- visl_transtime_ms: Simulated process time in milliseconds. Slowing down the
+  decoding speed can be useful for debugging.
+
+- visl_dprintk_frame_start, visl_dprintk_frame_nframes: Dictates a range of
+  frames where dprintk is activated. This only controls the dprintk tracing on a
+  per-frame basis. Note that printing a lot of data can be slow through serial.
+
+- keep_bitstream_buffers: Controls whether bitstream (i.e. OUTPUT) buffers are
+  kept after a decoding session. Defaults to false so as to reduce the amount of
+  clutter. keep_bitstream_buffers == false works well when live debugging the
+  client program with GDB.
+
+- bitstream_trace_frame_start, bitstream_trace_nframes: Similar to
+  visl_dprintk_frame_start, visl_dprintk_nframes, but controls the dumping of
+  buffer data through debugfs instead.
+
+What is the default use case for this driver?
+---------------------------------------------
+
+This driver can be used as a way to compare different userspace implementations.
+This assumes that a working client is run against visl and that the ftrace and
+OUTPUT buffer data is subsequently used to debug a work-in-progress
+implementation.
+
+Information on reference frames, their timestamps, the status of the OUTPUT and
+CAPTURE queues and more can be read directly from the CAPTURE buffers.
+
+Supported codecs
+----------------
+
+The following codecs are supported:
+
+- FWHT
+- MPEG2
+- VP8
+- VP9
+- H.264
+- HEVC
+
+visl trace events
+-----------------
+The trace events are defined on a per-codec basis, e.g.:
+
+.. code-block:: bash
+
+        $ ls /sys/kernel/debug/tracing/events/ | grep visl
+        visl_fwht_controls
+        visl_h264_controls
+        visl_hevc_controls
+        visl_mpeg2_controls
+        visl_vp8_controls
+        visl_vp9_controls
+
+For example, in order to dump HEVC SPS data:
+
+.. code-block:: bash
+
+        $ echo 1 >  /sys/kernel/debug/tracing/events/visl_hevc_controls/v4l2_ctrl_hevc_sps/enable
+
+The SPS data will be dumped to the trace buffer, i.e.:
+
+.. code-block:: bash
+
+        $ cat /sys/kernel/debug/tracing/trace
+        video_parameter_set_id 0
+        seq_parameter_set_id 0
+        pic_width_in_luma_samples 1920
+        pic_height_in_luma_samples 1080
+        bit_depth_luma_minus8 0
+        bit_depth_chroma_minus8 0
+        log2_max_pic_order_cnt_lsb_minus4 4
+        sps_max_dec_pic_buffering_minus1 6
+        sps_max_num_reorder_pics 2
+        sps_max_latency_increase_plus1 0
+        log2_min_luma_coding_block_size_minus3 0
+        log2_diff_max_min_luma_coding_block_size 3
+        log2_min_luma_transform_block_size_minus2 0
+        log2_diff_max_min_luma_transform_block_size 3
+        max_transform_hierarchy_depth_inter 2
+        max_transform_hierarchy_depth_intra 2
+        pcm_sample_bit_depth_luma_minus1 0
+        pcm_sample_bit_depth_chroma_minus1 0
+        log2_min_pcm_luma_coding_block_size_minus3 0
+        log2_diff_max_min_pcm_luma_coding_block_size 0
+        num_short_term_ref_pic_sets 0
+        num_long_term_ref_pics_sps 0
+        chroma_format_idc 1
+        sps_max_sub_layers_minus1 0
+        flags AMP_ENABLED|SAMPLE_ADAPTIVE_OFFSET|TEMPORAL_MVP_ENABLED|STRONG_INTRA_SMOOTHING_ENABLED
+
+
+Dumping OUTPUT buffer data through debugfs
+------------------------------------------
+
+If the **VISL_DEBUGFS** Kconfig is enabled, visl will populate
+**/sys/kernel/debug/visl/bitstream** with OUTPUT buffer data according to the
+values of bitstream_trace_frame_start and bitstream_trace_nframes. This can
+highlight errors as broken clients may fail to fill the buffers properly.
+
+A single file is created for each processed OUTPUT buffer. Its name contains an
+integer that denotes the buffer sequence, i.e.:
+
+.. code-block:: c
+
+	snprintf(name, 32, "bitstream%d", run->src->sequence);
+
+Dumping the values is simply a matter of reading from the file, i.e.:
+
+For the buffer with sequence == 0:
+
+.. code-block:: bash
+
+        $ xxd /sys/kernel/debug/visl/bitstream/bitstream0
+        00000000: 2601 af04 d088 bc25 a173 0e41 a4f2 3274  &......%.s.A..2t
+        00000010: c668 cb28 e775 b4ac f53a ba60 f8fd 3aa1  .h.(.u...:.`..:.
+        00000020: 46b4 bcfc 506c e227 2372 e5f5 d7ea 579f  F...Pl.'#r....W.
+        00000030: 6371 5eb5 0eb8 23b5 ca6a 5de5 983a 19e4  cq^...#..j]..:..
+        00000040: e8c3 4320 b4ba a226 cbc1 4138 3a12 32d6  ..C ...&..A8:.2.
+        00000050: fef3 247b 3523 4e90 9682 ac8e eb0c a389  ..${5#N.........
+        00000060: ddd0 6cfc 0187 0e20 7aae b15b 1812 3d33  ..l.... z..[..=3
+        00000070: e1c5 f425 a83a 00b7 4f18 8127 3c4c aefb  ...%.:..O..'<L..
+
+For the buffer with sequence == 1:
+
+.. code-block:: bash
+
+        $ xxd /sys/kernel/debug/visl/bitstream/bitstream1
+        00000000: 0201 d021 49e1 0c40 aa11 1449 14a6 01dc  ...!I..@...I....
+        00000010: 7023 889a c8cd 2cd0 13b4 dab0 e8ca 21fe  p#....,.......!.
+        00000020: c4c8 ab4c 486e 4e2f b0df 96cc c74e 8dde  ...LHnN/.....N..
+        00000030: 8ce7 ee36 d880 4095 4d64 30a0 ff4f 0c5e  ...6..@.Md0..O.^
+        00000040: f16b a6a1 d806 ca2a 0ece a673 7bea 1f37  .k.....*...s{..7
+        00000050: 370f 5bb9 1dc4 ba21 6434 bc53 0173 cba0  7.[....!d4.S.s..
+        00000060: dfe6 bc99 01ea b6e0 346b 92b5 c8de 9f5d  ........4k.....]
+        00000070: e7cc 3484 1769 fef2 a693 a945 2c8b 31da  ..4..i.....E,.1.
+
+And so on.
+
+By default, the files are removed during STREAMOFF. This is to reduce the amount
+of clutter.
diff --git a/MAINTAINERS b/MAINTAINERS
index 733d259cf1fc..375bf8ee1acb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21757,6 +21757,12 @@ F:	include/linux/virtio*.h
 F:	include/uapi/linux/virtio_*.h
 F:	tools/virtio/
 
+VISL VIRTUAL STATELESS DECODER DRIVER
+M:	Daniel Almeida <daniel.almeida@collabora.com>
+L:	linux-media@vger.kernel.org
+S:	Supported
+F:	drivers/media/test-drivers/visl
+
 IFCVF VIRTIO DATA PATH ACCELERATOR
 R:	Zhu Lingshan <lingshan.zhu@intel.com>
 F:	drivers/vdpa/ifcvf/
diff --git a/drivers/media/test-drivers/Kconfig b/drivers/media/test-drivers/Kconfig
index 51cf27834df0..459b433e9fae 100644
--- a/drivers/media/test-drivers/Kconfig
+++ b/drivers/media/test-drivers/Kconfig
@@ -20,6 +20,7 @@ config VIDEO_VIM2M
 source "drivers/media/test-drivers/vicodec/Kconfig"
 source "drivers/media/test-drivers/vimc/Kconfig"
 source "drivers/media/test-drivers/vivid/Kconfig"
+source "drivers/media/test-drivers/visl/Kconfig"
 
 endif #V4L_TEST_DRIVERS
 
diff --git a/drivers/media/test-drivers/Makefile b/drivers/media/test-drivers/Makefile
index ff390b687189..740714a4584d 100644
--- a/drivers/media/test-drivers/Makefile
+++ b/drivers/media/test-drivers/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_VIDEO_VICODEC) += vicodec/
 obj-$(CONFIG_VIDEO_VIM2M) += vim2m.o
 obj-$(CONFIG_VIDEO_VIMC) += vimc/
 obj-$(CONFIG_VIDEO_VIVID) += vivid/
+obj-$(CONFIG_VIDEO_VISL) += visl/
diff --git a/drivers/media/test-drivers/visl/Kconfig b/drivers/media/test-drivers/visl/Kconfig
new file mode 100644
index 000000000000..7508b904f196
--- /dev/null
+++ b/drivers/media/test-drivers/visl/Kconfig
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0+
+config VIDEO_VISL
+	tristate "Virtual Stateless Decoder Driver (visl)"
+	depends on VIDEO_DEV
+	select FONT_SUPPORT
+	select FONT_8x16
+	select VIDEOBUF2_VMALLOC
+	select V4L2_MEM2MEM_DEV
+	select MEDIA_CONTROLLER
+	select MEDIA_CONTROLLER_REQUEST_API
+	select VIDEO_V4L2_TPG
+	help
+
+	  A virtual stateless decoder device for uAPI development purposes.
+
+	  A userspace implementation can use visl to run a decoding loop even
+	  when no hardware is available or when the kernel uAPI for the codec
+	  has not been upstreamed yet. This can reveal bugs at an early stage.
+
+	  When in doubt, say N.
+
+config VISL_DEBUGFS
+	bool "Enable debugfs for visl"
+	depends on VIDEO_VISL
+	depends on DEBUG_FS
+
+	help
+	  Choose Y to dump the bitstream buffers through debugfs.
+	  When in doubt, say N.
diff --git a/drivers/media/test-drivers/visl/Makefile b/drivers/media/test-drivers/visl/Makefile
new file mode 100644
index 000000000000..fb4d5ae1b17f
--- /dev/null
+++ b/drivers/media/test-drivers/visl/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0+
+visl-y := visl-core.o visl-video.o visl-dec.o visl-trace-points.o
+
+ifeq ($(CONFIG_VISL_DEBUGFS),y)
+  visl-y += visl-debugfs.o
+endif
+
+obj-$(CONFIG_VIDEO_VISL) += visl.o
diff --git a/drivers/media/test-drivers/visl/visl-core.c b/drivers/media/test-drivers/visl/visl-core.c
new file mode 100644
index 000000000000..9cb60ab653bf
--- /dev/null
+++ b/drivers/media/test-drivers/visl/visl-core.c
@@ -0,0 +1,541 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A virtual stateless decoder device for stateless uAPI development purposes.
+ *
+ * This tool's objective is to help the development and testing of userspace
+ * applications that use the V4L2 stateless API to decode media.
+ *
+ * A userspace implementation can use visl to run a decoding loop even when no
+ * hardware is available or when the kernel uAPI for the codec has not been
+ * upstreamed yet. This can reveal bugs at an early stage.
+ *
+ * This driver can also trace the contents of the V4L2 controls submitted to it.
+ * It can also dump the contents of the vb2 buffers through a debugfs
+ * interface. This is in many ways similar to the tracing infrastructure
+ * available for other popular encode/decode APIs out there and can help develop
+ * a userspace application by using another (working) one as a reference.
+ *
+ * Note that no actual decoding of video frames is performed by visl. The V4L2
+ * test pattern generator is used to write various debug information to the
+ * capture buffers instead.
+ *
+ * Copyright (C) 2022 Collabora, Ltd.
+ *
+ * Based on the vim2m driver, that is:
+ *
+ * Copyright (c) 2009-2010 Samsung Electronics Co., Ltd.
+ * Pawel Osciak, <pawel@osciak.com>
+ * Marek Szyprowski, <m.szyprowski@samsung.com>
+ *
+ * Based on the vicodec driver, that is:
+ *
+ * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * Based on the Cedrus VPU driver, that is:
+ *
+ * Copyright (C) 2016 Florent Revest <florent.revest@free-electrons.com>
+ * Copyright (C) 2018 Paul Kocialkowski <paul.kocialkowski@bootlin.com>
+ * Copyright (C) 2018 Bootlin
+ */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <media/v4l2-ctrls.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-ioctl.h>
+#include <media/v4l2-mem2mem.h>
+
+#include "visl.h"
+#include "visl-dec.h"
+#include "visl-debugfs.h"
+#include "visl-video.h"
+
+unsigned int visl_debug;
+module_param(visl_debug, uint, 0644);
+MODULE_PARM_DESC(visl_debug, " activates debug info");
+
+unsigned int visl_transtime_ms;
+module_param(visl_transtime_ms, uint, 0644);
+MODULE_PARM_DESC(visl_transtime_ms, " simulated process time in milliseconds.");
+
+/*
+ * dprintk can be slow through serial. This lets one limit the tracing to a
+ * particular number of frames
+ */
+int visl_dprintk_frame_start = -1;
+module_param(visl_dprintk_frame_start, int, 0);
+MODULE_PARM_DESC(visl_dprintk_frame_start,
+		 " a frame number to start tracing with dprintk");
+
+unsigned int visl_dprintk_nframes;
+module_param(visl_dprintk_nframes, uint, 0);
+MODULE_PARM_DESC(visl_dprintk_nframes,
+		 " the number of frames to trace with dprintk");
+
+bool keep_bitstream_buffers;
+module_param(keep_bitstream_buffers, bool, false);
+MODULE_PARM_DESC(keep_bitstream_buffers,
+		 " keep bitstream buffers in debugfs after streaming is stopped");
+
+int bitstream_trace_frame_start = -1;
+module_param(bitstream_trace_frame_start, int, 0);
+MODULE_PARM_DESC(bitstream_trace_frame_start,
+		 " a frame number to start dumping the bitstream through debugfs");
+
+unsigned int bitstream_trace_nframes;
+module_param(bitstream_trace_nframes, uint, 0);
+MODULE_PARM_DESC(bitstream_trace_nframes,
+		 " the number of frames to dump the bitstream through debugfs");
+
+static const struct visl_ctrl_desc visl_fwht_ctrl_descs[] = {
+	{
+		.cfg.id = V4L2_CID_STATELESS_FWHT_PARAMS,
+	},
+};
+
+const struct visl_ctrls visl_fwht_ctrls = {
+	.ctrls = visl_fwht_ctrl_descs,
+	.num_ctrls = ARRAY_SIZE(visl_fwht_ctrl_descs)
+};
+
+static const struct visl_ctrl_desc visl_mpeg2_ctrl_descs[] = {
+	{
+		.cfg.id = V4L2_CID_STATELESS_MPEG2_SEQUENCE,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_MPEG2_PICTURE,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_MPEG2_QUANTISATION,
+	},
+};
+
+const struct visl_ctrls visl_mpeg2_ctrls = {
+	.ctrls = visl_mpeg2_ctrl_descs,
+	.num_ctrls = ARRAY_SIZE(visl_mpeg2_ctrl_descs),
+};
+
+static const struct visl_ctrl_desc visl_vp8_ctrl_descs[] = {
+	{
+		.cfg.id = V4L2_CID_STATELESS_VP8_FRAME,
+	},
+};
+
+const struct visl_ctrls visl_vp8_ctrls = {
+	.ctrls = visl_vp8_ctrl_descs,
+	.num_ctrls = ARRAY_SIZE(visl_vp8_ctrl_descs),
+};
+
+static const struct visl_ctrl_desc visl_vp9_ctrl_descs[] = {
+	{
+		.cfg.id = V4L2_CID_STATELESS_VP9_FRAME,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_VP9_COMPRESSED_HDR,
+	},
+};
+
+const struct visl_ctrls visl_vp9_ctrls = {
+	.ctrls = visl_vp9_ctrl_descs,
+	.num_ctrls = ARRAY_SIZE(visl_vp9_ctrl_descs),
+};
+
+static const struct visl_ctrl_desc visl_h264_ctrl_descs[] = {
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_DECODE_PARAMS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_SPS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_PPS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_SCALING_MATRIX,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_DECODE_MODE,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_START_CODE,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_SLICE_PARAMS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_H264_PRED_WEIGHTS,
+	},
+};
+
+const struct visl_ctrls visl_h264_ctrls = {
+	.ctrls = visl_h264_ctrl_descs,
+	.num_ctrls = ARRAY_SIZE(visl_h264_ctrl_descs),
+};
+
+static const struct visl_ctrl_desc visl_hevc_ctrl_descs[] = {
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_SPS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_PPS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_SLICE_PARAMS,
+		/* The absolute maximum for level > 6 */
+		.cfg.dims = { 600 },
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_SCALING_MATRIX,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_DECODE_PARAMS,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_DECODE_MODE,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_START_CODE,
+	},
+	{
+		.cfg.id = V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS,
+		.cfg.dims = { 256 },
+		.cfg.max = 0xffffffff,
+		.cfg.step = 1,
+	},
+
+};
+
+const struct visl_ctrls visl_hevc_ctrls = {
+	.ctrls = visl_hevc_ctrl_descs,
+	.num_ctrls = ARRAY_SIZE(visl_hevc_ctrl_descs),
+};
+
+struct v4l2_ctrl *visl_find_control(struct visl_ctx *ctx, u32 id)
+{
+	struct v4l2_ctrl_handler *hdl = &ctx->hdl;
+
+	return v4l2_ctrl_find(hdl, id);
+}
+
+void *visl_find_control_data(struct visl_ctx *ctx, u32 id)
+{
+	struct v4l2_ctrl *ctrl;
+
+	ctrl = visl_find_control(ctx, id);
+	if (ctrl)
+		return ctrl->p_cur.p;
+
+	return NULL;
+}
+
+u32 visl_control_num_elems(struct visl_ctx *ctx, u32 id)
+{
+	struct v4l2_ctrl *ctrl;
+
+	ctrl = visl_find_control(ctx, id);
+	if (ctrl)
+		return ctrl->elems;
+
+	return 0;
+}
+
+static void visl_device_release(struct video_device *vdev)
+{
+	struct visl_dev *dev = container_of(vdev, struct visl_dev, vfd);
+
+	v4l2_device_unregister(&dev->v4l2_dev);
+	v4l2_m2m_release(dev->m2m_dev);
+	media_device_cleanup(&dev->mdev);
+	visl_debugfs_deinit(dev);
+	kfree(dev);
+}
+
+#define VISL_CONTROLS_COUNT	ARRAY_SIZE(visl_controls)
+
+static int visl_init_ctrls(struct visl_ctx *ctx)
+{
+	struct visl_dev *dev = ctx->dev;
+	struct v4l2_ctrl_handler *hdl = &ctx->hdl;
+	unsigned int ctrl_cnt = 0;
+	unsigned int i;
+	unsigned int j;
+	const struct visl_ctrls *ctrls;
+
+	for (i = 0; i < num_coded_fmts; i++)
+		ctrl_cnt += visl_coded_fmts[i].ctrls->num_ctrls;
+
+	v4l2_ctrl_handler_init(hdl, ctrl_cnt);
+
+	for (i = 0; i < num_coded_fmts; i++) {
+		ctrls = visl_coded_fmts[i].ctrls;
+		for (j = 0; j < ctrls->num_ctrls; j++)
+			v4l2_ctrl_new_custom(hdl, &ctrls->ctrls[j].cfg, NULL);
+	}
+
+	if (hdl->error) {
+		v4l2_err(&dev->v4l2_dev,
+			 "Failed to initialize control handler\n");
+		v4l2_ctrl_handler_free(hdl);
+		return hdl->error;
+	}
+
+	ctx->fh.ctrl_handler = hdl;
+	v4l2_ctrl_handler_setup(hdl);
+
+	return 0;
+}
+
+static int visl_open(struct file *file)
+{
+	struct visl_dev *dev = video_drvdata(file);
+	struct visl_ctx *ctx = NULL;
+	int rc = 0;
+
+	if (mutex_lock_interruptible(&dev->dev_mutex))
+		return -ERESTARTSYS;
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx) {
+		rc = -ENOMEM;
+		goto unlock;
+	}
+
+	ctx->tpg_str_buf = kzalloc(TPG_STR_BUF_SZ, GFP_KERNEL);
+
+	v4l2_fh_init(&ctx->fh, video_devdata(file));
+	file->private_data = &ctx->fh;
+	ctx->dev = dev;
+
+	rc = visl_init_ctrls(ctx);
+	if (rc)
+		goto free_ctx;
+
+	ctx->fh.m2m_ctx = v4l2_m2m_ctx_init(dev->m2m_dev, ctx, &visl_queue_init);
+
+	mutex_init(&ctx->vb_mutex);
+
+	if (IS_ERR(ctx->fh.m2m_ctx)) {
+		rc = PTR_ERR(ctx->fh.m2m_ctx);
+		goto free_hdl;
+	}
+
+	rc = visl_set_default_format(ctx);
+	if (rc)
+		goto free_m2m_ctx;
+
+	v4l2_fh_add(&ctx->fh);
+
+	dprintk(dev, "Created instance: %p, m2m_ctx: %p\n",
+		ctx, ctx->fh.m2m_ctx);
+
+	mutex_unlock(&dev->dev_mutex);
+	return rc;
+
+free_m2m_ctx:
+	v4l2_m2m_ctx_release(ctx->fh.m2m_ctx);
+free_hdl:
+	v4l2_ctrl_handler_free(&ctx->hdl);
+	v4l2_fh_exit(&ctx->fh);
+free_ctx:
+	kfree(ctx->tpg_str_buf);
+	kfree(ctx);
+unlock:
+	mutex_unlock(&dev->dev_mutex);
+	return rc;
+}
+
+static int visl_release(struct file *file)
+{
+	struct visl_dev *dev = video_drvdata(file);
+	struct visl_ctx *ctx = visl_file_to_ctx(file);
+
+	dprintk(dev, "Releasing instance %p\n", ctx);
+
+	tpg_free(&ctx->tpg);
+	v4l2_fh_del(&ctx->fh);
+	v4l2_fh_exit(&ctx->fh);
+	v4l2_ctrl_handler_free(&ctx->hdl);
+	mutex_lock(&dev->dev_mutex);
+	v4l2_m2m_ctx_release(ctx->fh.m2m_ctx);
+	mutex_unlock(&dev->dev_mutex);
+
+	kfree(ctx->tpg_str_buf);
+	kfree(ctx);
+
+	return 0;
+}
+
+static const struct v4l2_file_operations visl_fops = {
+	.owner		= THIS_MODULE,
+	.open		= visl_open,
+	.release	= visl_release,
+	.poll		= v4l2_m2m_fop_poll,
+	.unlocked_ioctl	= video_ioctl2,
+	.mmap		= v4l2_m2m_fop_mmap,
+};
+
+static const struct video_device visl_videodev = {
+	.name		= VISL_NAME,
+	.vfl_dir	= VFL_DIR_M2M,
+	.fops		= &visl_fops,
+	.ioctl_ops	= &visl_ioctl_ops,
+	.minor		= -1,
+	.release	= visl_device_release,
+	.device_caps	= V4L2_CAP_VIDEO_M2M_MPLANE | V4L2_CAP_STREAMING,
+};
+
+static const struct v4l2_m2m_ops visl_m2m_ops = {
+	.device_run	= visl_device_run,
+};
+
+static const struct media_device_ops visl_m2m_media_ops = {
+	.req_validate	= visl_request_validate,
+	.req_queue	= v4l2_m2m_request_queue,
+};
+
+static int visl_probe(struct platform_device *pdev)
+{
+	struct visl_dev *dev;
+	struct video_device *vfd;
+	int ret;
+	int rc;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
+	if (ret)
+		goto error_visl_dev;
+
+	mutex_init(&dev->dev_mutex);
+
+	dev->vfd = visl_videodev;
+	vfd = &dev->vfd;
+	vfd->lock = &dev->dev_mutex;
+	vfd->v4l2_dev = &dev->v4l2_dev;
+
+	video_set_drvdata(vfd, dev);
+
+	platform_set_drvdata(pdev, dev);
+
+	dev->m2m_dev = v4l2_m2m_init(&visl_m2m_ops);
+	if (IS_ERR(dev->m2m_dev)) {
+		v4l2_err(&dev->v4l2_dev, "Failed to init mem2mem device\n");
+		ret = PTR_ERR(dev->m2m_dev);
+		dev->m2m_dev = NULL;
+		goto error_dev;
+	}
+
+	dev->mdev.dev = &pdev->dev;
+	strscpy(dev->mdev.model, "visl", sizeof(dev->mdev.model));
+	strscpy(dev->mdev.bus_info, "platform:visl",
+		sizeof(dev->mdev.bus_info));
+	media_device_init(&dev->mdev);
+	dev->mdev.ops = &visl_m2m_media_ops;
+	dev->v4l2_dev.mdev = &dev->mdev;
+
+	ret = video_register_device(vfd, VFL_TYPE_VIDEO, -1);
+	if (ret) {
+		v4l2_err(&dev->v4l2_dev, "Failed to register video device\n");
+		goto error_m2m;
+	}
+
+	v4l2_info(&dev->v4l2_dev,
+		  "Device registered as /dev/video%d\n", vfd->num);
+
+	ret = v4l2_m2m_register_media_controller(dev->m2m_dev, vfd,
+						 MEDIA_ENT_F_PROC_VIDEO_DECODER);
+	if (ret) {
+		v4l2_err(&dev->v4l2_dev, "Failed to init mem2mem media controller\n");
+		goto error_v4l2;
+	}
+
+	ret = media_device_register(&dev->mdev);
+	if (ret) {
+		v4l2_err(&dev->v4l2_dev, "Failed to register mem2mem media device\n");
+		goto error_m2m_mc;
+	}
+
+	rc = visl_debugfs_init(dev);
+	if (rc)
+		dprintk(dev, "visl_debugfs_init failed: %d\n"
+			"Continuing without debugfs support\n", rc);
+
+	return 0;
+
+error_m2m_mc:
+	v4l2_m2m_unregister_media_controller(dev->m2m_dev);
+error_v4l2:
+	video_unregister_device(&dev->vfd);
+	/* visl_device_release called by video_unregister_device to release various objects */
+	return ret;
+error_m2m:
+	v4l2_m2m_release(dev->m2m_dev);
+error_dev:
+	v4l2_device_unregister(&dev->v4l2_dev);
+error_visl_dev:
+	kfree(dev);
+
+	return ret;
+}
+
+static int visl_remove(struct platform_device *pdev)
+{
+	struct visl_dev *dev = platform_get_drvdata(pdev);
+
+	v4l2_info(&dev->v4l2_dev, "Removing " VISL_NAME);
+
+#ifdef CONFIG_MEDIA_CONTROLLER
+	if (media_devnode_is_registered(dev->mdev.devnode)) {
+		media_device_unregister(&dev->mdev);
+		v4l2_m2m_unregister_media_controller(dev->m2m_dev);
+	}
+#endif
+	video_unregister_device(&dev->vfd);
+
+	return 0;
+}
+
+static struct platform_driver visl_pdrv = {
+	.probe		= visl_probe,
+	.remove		= visl_remove,
+	.driver		= {
+		.name	= VISL_NAME,
+	},
+};
+
+static void visl_dev_release(struct device *dev) {}
+
+static struct platform_device visl_pdev = {
+	.name		= VISL_NAME,
+	.dev.release	= visl_dev_release,
+};
+
+static void __exit visl_exit(void)
+{
+	platform_driver_unregister(&visl_pdrv);
+	platform_device_unregister(&visl_pdev);
+}
+
+static int __init visl_init(void)
+{
+	int ret;
+
+	ret = platform_device_register(&visl_pdev);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&visl_pdrv);
+	if (ret)
+		platform_device_unregister(&visl_pdev);
+
+	return ret;
+}
+
+MODULE_DESCRIPTION("Virtual stateless decoder device");
+MODULE_AUTHOR("Daniel Almeida <daniel.almeida@collabora.com>");
+MODULE_LICENSE("GPL");
+
+module_init(visl_init);
+module_exit(visl_exit);
diff --git a/drivers/media/test-drivers/visl/visl-debugfs.c b/drivers/media/test-drivers/visl/visl-debugfs.c
new file mode 100644
index 000000000000..45f2a8268014
--- /dev/null
+++ b/drivers/media/test-drivers/visl/visl-debugfs.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Debugfs tracing for bitstream buffers. This is similar to VA-API's
+ * LIBVA_TRACE_BUFDATA in that the raw bitstream can be dumped as a debugging
+ * aid.
+ *
+ * Produces one file per OUTPUT buffer. Files are automatically cleared on
+ * STREAMOFF unless the module parameter "keep_bitstream_buffers" is set.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <media/v4l2-mem2mem.h>
+
+#include "visl-debugfs.h"
+
+int visl_debugfs_init(struct visl_dev *dev)
+{
+	dev->debugfs_root = debugfs_create_dir("visl", NULL);
+	INIT_LIST_HEAD(&dev->bitstream_blobs);
+	mutex_init(&dev->bitstream_lock);
+
+	if (IS_ERR(dev->debugfs_root))
+		return PTR_ERR(dev->debugfs_root);
+
+	return visl_debugfs_bitstream_init(dev);
+}
+
+int visl_debugfs_bitstream_init(struct visl_dev *dev)
+{
+	dev->bitstream_debugfs = debugfs_create_dir("bitstream",
+						    dev->debugfs_root);
+	if (IS_ERR(dev->bitstream_debugfs))
+		return PTR_ERR(dev->bitstream_debugfs);
+
+	return 0;
+}
+
+void visl_trace_bitstream(struct visl_ctx *ctx, struct visl_run *run)
+{
+	u8 *vaddr = vb2_plane_vaddr(&run->src->vb2_buf, 0);
+	struct visl_blob *blob;
+	size_t data_sz = vb2_get_plane_payload(&run->src->vb2_buf, 0);
+	struct dentry *dentry;
+	char name[32];
+
+	blob  = kzalloc(sizeof(*blob), GFP_KERNEL);
+	if (!blob)
+		return;
+
+	blob->blob.data = vzalloc(data_sz);
+	if (!blob->blob.data)
+		goto err_vmalloc;
+
+	blob->blob.size = data_sz;
+	snprintf(name, 32, "bitstream%d", run->src->sequence);
+
+	memcpy(blob->blob.data, vaddr, data_sz);
+
+	dentry = debugfs_create_blob(name, 0444, ctx->dev->bitstream_debugfs,
+				     &blob->blob);
+	if (IS_ERR(dentry))
+		goto err_debugfs;
+
+	blob->dentry = dentry;
+
+	mutex_lock(&ctx->dev->bitstream_lock);