summaryrefslogtreecommitdiffstats
path: root/drivers/media/platform/allegro-dvt/nal-h264.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/media/platform/allegro-dvt/nal-h264.c')
-rw-r--r--drivers/media/platform/allegro-dvt/nal-h264.c605
1 files changed, 605 insertions, 0 deletions
diff --git a/drivers/media/platform/allegro-dvt/nal-h264.c b/drivers/media/platform/allegro-dvt/nal-h264.c
new file mode 100644
index 000000000..326637663
--- /dev/null
+++ b/drivers/media/platform/allegro-dvt/nal-h264.c
@@ -0,0 +1,605 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Pengutronix, Michael Tretter <kernel@pengutronix.de>
+ *
+ * Convert NAL units between raw byte sequence payloads (RBSP) and C structs
+ *
+ * The conversion is defined in "ITU-T Rec. H.264 (04/2017) Advanced video
+ * coding for generic audiovisual services". Decoder drivers may use the
+ * parser to parse RBSP from encoded streams and configure the hardware, if
+ * the hardware is not able to parse RBSP itself. Encoder drivers may use the
+ * generator to generate the RBSP for SPS/PPS nal units and add them to the
+ * encoded stream if the hardware does not generate the units.
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/v4l2-controls.h>
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/log2.h>
+
+#include "nal-h264.h"
+#include "nal-rbsp.h"
+
+/*
+ * See Rec. ITU-T H.264 (04/2017) Table 7-1 - NAL unit type codes, syntax
+ * element categories, and NAL unit type classes
+ */
+enum nal_unit_type {
+ SEQUENCE_PARAMETER_SET = 7,
+ PICTURE_PARAMETER_SET = 8,
+ FILLER_DATA = 12,
+};
+
+static void nal_h264_write_start_code_prefix(struct rbsp *rbsp)
+{
+ u8 *p = rbsp->data + DIV_ROUND_UP(rbsp->pos, 8);
+ int i = 4;
+
+ if (DIV_ROUND_UP(rbsp->pos, 8) + i > rbsp->size) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ p[0] = 0x00;
+ p[1] = 0x00;
+ p[2] = 0x00;
+ p[3] = 0x01;
+
+ rbsp->pos += i * 8;
+}
+
+static void nal_h264_read_start_code_prefix(struct rbsp *rbsp)
+{
+ u8 *p = rbsp->data + DIV_ROUND_UP(rbsp->pos, 8);
+ int i = 4;
+
+ if (DIV_ROUND_UP(rbsp->pos, 8) + i > rbsp->size) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ if (p[0] != 0x00 || p[1] != 0x00 || p[2] != 0x00 || p[3] != 0x01) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ rbsp->pos += i * 8;
+}
+
+static void nal_h264_write_filler_data(struct rbsp *rbsp)
+{
+ u8 *p = rbsp->data + DIV_ROUND_UP(rbsp->pos, 8);
+ int i;
+
+ /* Keep 1 byte extra for terminating the NAL unit */
+ i = rbsp->size - DIV_ROUND_UP(rbsp->pos, 8) - 1;
+ memset(p, 0xff, i);
+ rbsp->pos += i * 8;
+}
+
+static void nal_h264_read_filler_data(struct rbsp *rbsp)
+{
+ u8 *p = rbsp->data + DIV_ROUND_UP(rbsp->pos, 8);
+
+ while (*p == 0xff) {
+ if (DIV_ROUND_UP(rbsp->pos, 8) > rbsp->size) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ p++;
+ rbsp->pos += 8;
+ }
+}
+
+static void nal_h264_rbsp_hrd_parameters(struct rbsp *rbsp,
+ struct nal_h264_hrd_parameters *hrd)
+{
+ unsigned int i;
+
+ if (!hrd) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ rbsp_uev(rbsp, &hrd->cpb_cnt_minus1);
+ rbsp_bits(rbsp, 4, &hrd->bit_rate_scale);
+ rbsp_bits(rbsp, 4, &hrd->cpb_size_scale);
+
+ for (i = 0; i <= hrd->cpb_cnt_minus1; i++) {
+ rbsp_uev(rbsp, &hrd->bit_rate_value_minus1[i]);
+ rbsp_uev(rbsp, &hrd->cpb_size_value_minus1[i]);
+ rbsp_bit(rbsp, &hrd->cbr_flag[i]);
+ }
+
+ rbsp_bits(rbsp, 5, &hrd->initial_cpb_removal_delay_length_minus1);
+ rbsp_bits(rbsp, 5, &hrd->cpb_removal_delay_length_minus1);
+ rbsp_bits(rbsp, 5, &hrd->dpb_output_delay_length_minus1);
+ rbsp_bits(rbsp, 5, &hrd->time_offset_length);
+}
+
+static void nal_h264_rbsp_vui_parameters(struct rbsp *rbsp,
+ struct nal_h264_vui_parameters *vui)
+{
+ if (!vui) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ rbsp_bit(rbsp, &vui->aspect_ratio_info_present_flag);
+ if (vui->aspect_ratio_info_present_flag) {
+ rbsp_bits(rbsp, 8, &vui->aspect_ratio_idc);
+ if (vui->aspect_ratio_idc == 255) {
+ rbsp_bits(rbsp, 16, &vui->sar_width);
+ rbsp_bits(rbsp, 16, &vui->sar_height);
+ }
+ }
+
+ rbsp_bit(rbsp, &vui->overscan_info_present_flag);
+ if (vui->overscan_info_present_flag)
+ rbsp_bit(rbsp, &vui->overscan_appropriate_flag);
+
+ rbsp_bit(rbsp, &vui->video_signal_type_present_flag);
+ if (vui->video_signal_type_present_flag) {
+ rbsp_bits(rbsp, 3, &vui->video_format);
+ rbsp_bit(rbsp, &vui->video_full_range_flag);
+
+ rbsp_bit(rbsp, &vui->colour_description_present_flag);
+ if (vui->colour_description_present_flag) {
+ rbsp_bits(rbsp, 8, &vui->colour_primaries);
+ rbsp_bits(rbsp, 8, &vui->transfer_characteristics);
+ rbsp_bits(rbsp, 8, &vui->matrix_coefficients);
+ }
+ }
+
+ rbsp_bit(rbsp, &vui->chroma_loc_info_present_flag);
+ if (vui->chroma_loc_info_present_flag) {
+ rbsp_uev(rbsp, &vui->chroma_sample_loc_type_top_field);
+ rbsp_uev(rbsp, &vui->chroma_sample_loc_type_bottom_field);
+ }
+
+ rbsp_bit(rbsp, &vui->timing_info_present_flag);
+ if (vui->timing_info_present_flag) {
+ rbsp_bits(rbsp, 32, &vui->num_units_in_tick);
+ rbsp_bits(rbsp, 32, &vui->time_scale);
+ rbsp_bit(rbsp, &vui->fixed_frame_rate_flag);
+ }
+
+ rbsp_bit(rbsp, &vui->nal_hrd_parameters_present_flag);
+ if (vui->nal_hrd_parameters_present_flag)
+ nal_h264_rbsp_hrd_parameters(rbsp, &vui->nal_hrd_parameters);
+
+ rbsp_bit(rbsp, &vui->vcl_hrd_parameters_present_flag);
+ if (vui->vcl_hrd_parameters_present_flag)
+ nal_h264_rbsp_hrd_parameters(rbsp, &vui->vcl_hrd_parameters);
+
+ if (vui->nal_hrd_parameters_present_flag ||
+ vui->vcl_hrd_parameters_present_flag)
+ rbsp_bit(rbsp, &vui->low_delay_hrd_flag);
+
+ rbsp_bit(rbsp, &vui->pic_struct_present_flag);
+
+ rbsp_bit(rbsp, &vui->bitstream_restriction_flag);
+ if (vui->bitstream_restriction_flag) {
+ rbsp_bit(rbsp, &vui->motion_vectors_over_pic_boundaries_flag);
+ rbsp_uev(rbsp, &vui->max_bytes_per_pic_denom);
+ rbsp_uev(rbsp, &vui->max_bits_per_mb_denom);
+ rbsp_uev(rbsp, &vui->log2_max_mv_length_horizontal);
+ rbsp_uev(rbsp, &vui->log21_max_mv_length_vertical);
+ rbsp_uev(rbsp, &vui->max_num_reorder_frames);
+ rbsp_uev(rbsp, &vui->max_dec_frame_buffering);
+ }
+}
+
+static void nal_h264_rbsp_sps(struct rbsp *rbsp, struct nal_h264_sps *sps)
+{
+ unsigned int i;
+
+ if (!sps) {
+ rbsp->error = -EINVAL;
+ return;
+ }
+
+ rbsp_bits(rbsp, 8, &sps->profile_idc);
+ rbsp_bit(rbsp, &sps->constraint_set0_flag);
+ rbsp_bit(rbsp, &sps->constraint_set1_flag);
+ rbsp_bit(rbsp, &sps->constraint_set2_flag);
+ rbsp_bit(rbsp, &sps->constraint_set3_flag);
+ rbsp_bit(rbsp, &sps->constraint_set4_flag);
+ rbsp_bit(rbsp, &sps->constraint_set5_flag);
+ rbsp_bits(rbsp, 2, &sps->reserved_zero_2bits);
+ rbsp_bits(rbsp, 8, &sps->level_idc);
+
+ rbsp_uev(rbsp, &sps->seq_parameter_set_id);
+
+ if (sps->profile_idc == 100 || sps->profile_idc == 110 ||
+ sps->profile_idc == 122 || sps->profile_idc == 244 ||
+ sps->profile_idc == 44 || sps->profile_idc == 83 ||
+ sps->profile_idc == 86 || sps->profile_idc == 118 ||
+ sps->profile_idc == 128 || sps->profile_idc == 138 ||
+ sps->profile_idc == 139 || sps->profile_idc == 134 ||
+ sps->profile_idc == 135) {
+ rbsp_uev(rbsp, &sps->chroma_format_idc);
+
+ if (sps->chroma_format_idc == 3)
+ rbsp_bit(rbsp, &sps->separate_colour_plane_flag);
+ rbsp_uev(rbsp, &sps->bit_depth_luma_minus8);
+ rbsp_uev(rbsp, &sps->bit_depth_chroma_minus8);
+ rbsp_bit(rbsp, &sps->qpprime_y_zero_transform_bypass_flag);
+ rbsp_bit(rbsp, &sps->seq_scaling_matrix_present_flag);
+ if (sps->seq_scaling_matrix_present_flag)
+ rbsp->error = -EINVAL;
+ }
+
+ rbsp_uev(rbsp, &sps->log2_max_frame_num_minus4);
+
+ rbsp_uev(rbsp, &sps->pic_order_cnt_type);
+ switch (sps->pic_order_cnt_type) {
+ case 0:
+ rbsp_uev(rbsp, &sps->log2_max_pic_order_cnt_lsb_minus4);
+ break;
+ case 1:
+ rbsp_bit(rbsp, &sps->delta_pic_order_always_zero_flag);
+ rbsp_sev(rbsp, &sps->offset_for_non_ref_pic);
+ rbsp_sev(rbsp, &sps->offset_for_top_to_bottom_field);
+
+ rbsp_uev(rbsp, &sps->num_ref_frames_in_pic_order_cnt_cycle);
+ for (i = 0; i < sps->num_ref_frames_in_pic_order_cnt_cycle; i++)
+ rbsp_sev(rbsp, &sps->offset_for_ref_frame[i]);
+ break;
+ default:
+ rbsp->error = -EINVAL;
+ break;
+ }
+
+ rbsp_uev(rbsp, &sps->max_num_ref_frames);
+ rbsp_bit(rbsp, &sps->gaps_in_frame_num_value_allowed_flag);
+ rbsp_uev(rbsp, &sps->pic_width_in_mbs_minus1);
+ rbsp_uev(rbsp, &sps->pic_height_in_map_units_minus1);
+
+ rbsp_bit(rbsp, &sps->frame_mbs_only_flag);
+ if (!sps->frame_mbs_only_flag)
+ rbsp_bit(rbsp, &sps->mb_adaptive_frame_field_flag);
+
+ rbsp_bit(rbsp, &sps->direct_8x8_inference_flag);
+
+ rbsp_bit(rbsp, &sps->frame_cropping_flag);
+ if (sps->frame_cropping_flag) {
+ rbsp_uev(rbsp, &sps->crop_left);
+ rbsp_uev(rbsp, &sps->crop_right);
+ rbsp_uev(rbsp, &sps->crop_top);
+ rbsp_uev(rbsp, &sps->crop_bottom);
+ }
+
+ rbsp_bit(rbsp, &sps->vui_parameters_present_flag);
+ if (sps->vui_parameters_present_flag)
+ nal_h264_rbsp_vui_parameters(rbsp, &sps->vui);
+}
+
+static void nal_h264_rbsp_pps(struct rbsp *rbsp, struct nal_h264_pps *pps)
+{
+ int i;
+
+ rbsp_uev(rbsp, &pps->pic_parameter_set_id);
+ rbsp_uev(rbsp, &pps->seq_parameter_set_id);
+ rbsp_bit(rbsp, &pps->entropy_coding_mode_flag);
+ rbsp_bit(rbsp, &pps->bottom_field_pic_order_in_frame_present_flag);
+ rbsp_uev(rbsp, &pps->num_slice_groups_minus1);
+ if (pps->num_slice_groups_minus1 > 0) {
+ rbsp_uev(rbsp, &pps->slice_group_map_type);
+ switch (pps->slice_group_map_type) {
+ case 0:
+ for (i = 0; i < pps->num_slice_groups_minus1; i++)
+ rbsp_uev(rbsp, &pps->run_length_minus1[i]);
+ break;
+ case 2:
+ for (i = 0; i < pps->num_slice_groups_minus1; i++) {
+ rbsp_uev(rbsp, &pps->top_left[i]);
+ rbsp_uev(rbsp, &pps->bottom_right[i]);
+ }
+ break;
+ case 3: case 4: case 5:
+ rbsp_bit(rbsp, &pps->slice_group_change_direction_flag);
+ rbsp_uev(rbsp, &pps->slice_group_change_rate_minus1);
+ break;
+ case 6:
+ rbsp_uev(rbsp, &pps->pic_size_in_map_units_minus1);
+ for (i = 0; i < pps->pic_size_in_map_units_minus1; i++)
+ rbsp_bits(rbsp,
+ order_base_2(pps->num_slice_groups_minus1 + 1),
+ &pps->slice_group_id[i]);
+ break;
+ default:
+ break;
+ }
+ }
+ rbsp_uev(rbsp, &pps->num_ref_idx_l0_default_active_minus1);
+ rbsp_uev(rbsp, &pps->num_ref_idx_l1_default_active_minus1);
+ rbsp_bit(rbsp, &pps->weighted_pred_flag);
+ rbsp_bits(rbsp, 2, &pps->weighted_bipred_idc);
+ rbsp_sev(rbsp, &pps->pic_init_qp_minus26);
+ rbsp_sev(rbsp, &pps->pic_init_qs_minus26);
+ rbsp_sev(rbsp, &pps->chroma_qp_index_offset);
+ rbsp_bit(rbsp, &pps->deblocking_filter_control_present_flag);
+ rbsp_bit(rbsp, &pps->constrained_intra_pred_flag);
+ rbsp_bit(rbsp, &pps->redundant_pic_cnt_present_flag);
+ if (/* more_rbsp_data() */ false) {
+ rbsp_bit(rbsp, &pps->transform_8x8_mode_flag);
+ rbsp_bit(rbsp, &pps->pic_scaling_matrix_present_flag);
+ if (pps->pic_scaling_matrix_present_flag)
+ rbsp->error = -EINVAL;
+ rbsp_sev(rbsp, &pps->second_chroma_qp_index_offset);
+ }
+}
+
+/**
+ * nal_h264_write_sps() - Write SPS NAL unit into RBSP format
+ * @dev: device pointer
+ * @dest: the buffer that is filled with RBSP data
+ * @n: maximum size of @dest in bytes
+ * @sps: &struct nal_h264_sps to convert to RBSP
+ *
+ * Convert @sps to RBSP data and write it into @dest.
+ *
+ * The size of the SPS NAL unit is not known in advance and this function will
+ * fail, if @dest does not hold sufficient space for the SPS NAL unit.
+ *
+ * Return: number of bytes written to @dest or negative error code
+ */
+ssize_t nal_h264_write_sps(const struct device *dev,
+ void *dest, size_t n, struct nal_h264_sps *sps)
+{
+ struct rbsp rbsp;
+ unsigned int forbidden_zero_bit = 0;
+ unsigned int nal_ref_idc = 0;
+ unsigned int nal_unit_type = SEQUENCE_PARAMETER_SET;
+
+ if (!dest)
+ return -EINVAL;
+
+ rbsp_init(&rbsp, dest, n, &write);
+
+ nal_h264_write_start_code_prefix(&rbsp);
+
+ rbsp_bit(&rbsp, &forbidden_zero_bit);
+ rbsp_bits(&rbsp, 2, &nal_ref_idc);
+ rbsp_bits(&rbsp, 5, &nal_unit_type);
+
+ nal_h264_rbsp_sps(&rbsp, sps);
+
+ rbsp_trailing_bits(&rbsp);
+
+ if (rbsp.error)
+ return rbsp.error;
+
+ return DIV_ROUND_UP(rbsp.pos, 8);
+}
+EXPORT_SYMBOL_GPL(nal_h264_write_sps);
+
+/**
+ * nal_h264_read_sps() - Read SPS NAL unit from RBSP format
+ * @dev: device pointer
+ * @sps: the &struct nal_h264_sps to fill from the RBSP data
+ * @src: the buffer that contains the RBSP data
+ * @n: size of @src in bytes
+ *
+ * Read RBSP data from @src and use it to fill @sps.
+ *
+ * Return: number of bytes read from @src or negative error code
+ */
+ssize_t nal_h264_read_sps(const struct device *dev,
+ struct nal_h264_sps *sps, void *src, size_t n)
+{
+ struct rbsp rbsp;
+ unsigned int forbidden_zero_bit;
+ unsigned int nal_ref_idc;
+ unsigned int nal_unit_type;
+
+ if (!src)
+ return -EINVAL;
+
+ rbsp_init(&rbsp, src, n, &read);
+
+ nal_h264_read_start_code_prefix(&rbsp);
+
+ rbsp_bit(&rbsp, &forbidden_zero_bit);
+ rbsp_bits(&rbsp, 2, &nal_ref_idc);
+ rbsp_bits(&rbsp, 5, &nal_unit_type);
+
+ if (rbsp.error ||
+ forbidden_zero_bit != 0 ||
+ nal_ref_idc != 0 ||
+ nal_unit_type != SEQUENCE_PARAMETER_SET)
+ return -EINVAL;
+
+ nal_h264_rbsp_sps(&rbsp, sps);
+
+ rbsp_trailing_bits(&rbsp);
+
+ if (rbsp.error)
+ return rbsp.error;
+
+ return DIV_ROUND_UP(rbsp.pos, 8);
+}
+EXPORT_SYMBOL_GPL(nal_h264_read_sps);
+
+/**
+ * nal_h264_write_pps() - Write PPS NAL unit into RBSP format
+ * @dev: device pointer
+ * @dest: the buffer that is filled with RBSP data
+ * @n: maximum size of @dest in bytes
+ * @pps: &struct nal_h264_pps to convert to RBSP
+ *
+ * Convert @pps to RBSP data and write it into @dest.
+ *
+ * The size of the PPS NAL unit is not known in advance and this function will
+ * fail, if @dest does not hold sufficient space for the PPS NAL unit.
+ *
+ * Return: number of bytes written to @dest or negative error code
+ */
+ssize_t nal_h264_write_pps(const struct device *dev,
+ void *dest, size_t n, struct nal_h264_pps *pps)
+{
+ struct rbsp rbsp;
+ unsigned int forbidden_zero_bit = 0;
+ unsigned int nal_ref_idc = 0;
+ unsigned int nal_unit_type = PICTURE_PARAMETER_SET;
+
+ if (!dest)
+ return -EINVAL;
+
+ rbsp_init(&rbsp, dest, n, &write);
+
+ nal_h264_write_start_code_prefix(&rbsp);
+
+ /* NAL unit header */
+ rbsp_bit(&rbsp, &forbidden_zero_bit);
+ rbsp_bits(&rbsp, 2, &nal_ref_idc);
+ rbsp_bits(&rbsp, 5, &nal_unit_type);
+
+ nal_h264_rbsp_pps(&rbsp, pps);
+
+ rbsp_trailing_bits(&rbsp);
+
+ if (rbsp.error)
+ return rbsp.error;
+
+ return DIV_ROUND_UP(rbsp.pos, 8);
+}
+EXPORT_SYMBOL_GPL(nal_h264_write_pps);
+
+/**
+ * nal_h264_read_pps() - Read PPS NAL unit from RBSP format
+ * @dev: device pointer
+ * @pps: the &struct nal_h264_pps to fill from the RBSP data
+ * @src: the buffer that contains the RBSP data
+ * @n: size of @src in bytes
+ *
+ * Read RBSP data from @src and use it to fill @pps.
+ *
+ * Return: number of bytes read from @src or negative error code
+ */
+ssize_t nal_h264_read_pps(const struct device *dev,
+ struct nal_h264_pps *pps, void *src, size_t n)
+{
+ struct rbsp rbsp;
+
+ if (!src)
+ return -EINVAL;
+
+ rbsp_init(&rbsp, src, n, &read);
+
+ nal_h264_read_start_code_prefix(&rbsp);
+
+ /* NAL unit header */
+ rbsp.pos += 8;
+
+ nal_h264_rbsp_pps(&rbsp, pps);
+
+ rbsp_trailing_bits(&rbsp);
+
+ if (rbsp.error)
+ return rbsp.error;
+
+ return DIV_ROUND_UP(rbsp.pos, 8);
+}
+EXPORT_SYMBOL_GPL(nal_h264_read_pps);
+
+/**
+ * nal_h264_write_filler() - Write filler data RBSP
+ * @dev: device pointer
+ * @dest: buffer to fill with filler data
+ * @n: size of the buffer to fill with filler data
+ *
+ * Write a filler data RBSP to @dest with a size of @n bytes and return the
+ * number of written filler data bytes.
+ *
+ * Use this function to generate dummy data in an RBSP data stream that can be
+ * safely ignored by h264 decoders.
+ *
+ * The RBSP format of the filler data is specified in Rec. ITU-T H.264
+ * (04/2017) 7.3.2.7 Filler data RBSP syntax.
+ *
+ * Return: number of filler data bytes (including marker) or negative error
+ */
+ssize_t nal_h264_write_filler(const struct device *dev, void *dest, size_t n)
+{
+ struct rbsp rbsp;
+ unsigned int forbidden_zero_bit = 0;
+ unsigned int nal_ref_idc = 0;
+ unsigned int nal_unit_type = FILLER_DATA;
+
+ if (!dest)
+ return -EINVAL;
+
+ rbsp_init(&rbsp, dest, n, &write);
+
+ nal_h264_write_start_code_prefix(&rbsp);
+
+ rbsp_bit(&rbsp, &forbidden_zero_bit);
+ rbsp_bits(&rbsp, 2, &nal_ref_idc);
+ rbsp_bits(&rbsp, 5, &nal_unit_type);
+
+ nal_h264_write_filler_data(&rbsp);
+
+ rbsp_trailing_bits(&rbsp);
+
+ return DIV_ROUND_UP(rbsp.pos, 8);
+}
+EXPORT_SYMBOL_GPL(nal_h264_write_filler);
+
+/**
+ * nal_h264_read_filler() - Read filler data RBSP
+ * @dev: device pointer
+ * @src: buffer with RBSP data that is read
+ * @n: maximum size of src that shall be read
+ *
+ * Read a filler data RBSP from @src up to a maximum size of @n bytes and
+ * return the size of the filler data in bytes including the marker.
+ *
+ * This function is used to parse filler data and skip the respective bytes in
+ * the RBSP data.
+ *
+ * The RBSP format of the filler data is specified in Rec. ITU-T H.264
+ * (04/2017) 7.3.2.7 Filler data RBSP syntax.
+ *
+ * Return: number of filler data bytes (including marker) or negative error
+ */
+ssize_t nal_h264_read_filler(const struct device *dev, void *src, size_t n)
+{
+ struct rbsp rbsp;
+ unsigned int forbidden_zero_bit;
+ unsigned int nal_ref_idc;
+ unsigned int nal_unit_type;
+
+ if (!src)
+ return -EINVAL;
+
+ rbsp_init(&rbsp, src, n, &read);
+
+ nal_h264_read_start_code_prefix(&rbsp);
+
+ rbsp_bit(&rbsp, &forbidden_zero_bit);
+ rbsp_bits(&rbsp, 2, &nal_ref_idc);
+ rbsp_bits(&rbsp, 5, &nal_unit_type);
+
+ if (rbsp.error)
+ return rbsp.error;
+ if (forbidden_zero_bit != 0 ||
+ nal_ref_idc != 0 ||
+ nal_unit_type != FILLER_DATA)
+ return -EINVAL;
+
+ nal_h264_read_filler_data(&rbsp);
+ rbsp_trailing_bits(&rbsp);
+
+ if (rbsp.error)
+ return rbsp.error;
+
+ return DIV_ROUND_UP(rbsp.pos, 8);
+}
+EXPORT_SYMBOL_GPL(nal_h264_read_filler);