path: root/drivers/media/test-drivers/vidtv/vidtv_psi.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains the logic to work with MPEG Program-Specific Information.
 * These are defined both in ISO/IEC 13818-1 (systems) and ETSI EN 300 468.
 * PSI is carried in the form of table structures, and although each table might
 * technically be broken into one or more sections, we do not do this here,
 * hence 'table' and 'section' are interchangeable for vidtv.
 *
 * This code currently supports three tables: PAT, PMT and SDT. These are the
 * bare minimum to get userspace to recognize our MPEG transport stream. It can
 * be extended to support more PSI tables in the future.
 *
 * Copyright (C) 2020 Daniel W. S. Almeida
 */

#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/crc32.h>
#include <linux/string.h>
#include <linux/printk.h>
#include <linux/ratelimit.h>
#include <linux/string.h>
#include <asm/byteorder.h>

#include "vidtv_psi.h"
#include "vidtv_common.h"
#include "vidtv_ts.h"

#define CRC_SIZE_IN_BYTES 4
#define MAX_VERSION_NUM 32

static const u32 CRC_LUT[256] = {
	/* from libdvbv5 */
	0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b,
	0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
	0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, 0x4c11db70, 0x48d0c6c7,
	0x4593e01e, 0x4152fda9, 0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
	0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3,
	0x709f7b7a, 0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
	0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58, 0xbaea46ef,
	0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
	0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 0xc7361b4c, 0xc3f706fb,
	0xceb42022, 0xca753d95, 0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
	0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0,
	0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
	0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 0x018aeb13, 0x054bf6a4,
	0x0808d07d, 0x0cc9cdca, 0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
	0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08,
	0x571d7dd1, 0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
	0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, 0xbb60adfc,
	0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
	0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a, 0xe0b41de7, 0xe4750050,
	0xe9362689, 0xedf73b3e, 0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
	0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34,
	0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
	0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb, 0x4f040d56, 0x4bc510e1,
	0x46863638, 0x42472b8f, 0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
	0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5,
	0x3f9b762c, 0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
	0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e, 0xf5ee4bb9,
	0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
	0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 0xc423cd6a, 0xc0e2d0dd,
	0xcda1f604, 0xc960ebb3, 0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
	0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71,
	0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
	0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, 0x4e8ee645, 0x4a4ffbf2,
	0x470cdd2b, 0x43cdc09c, 0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
	0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e,
	0x18197087, 0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
	0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d, 0x2056cd3a,
	0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
	0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c, 0xe3a1cbc1, 0xe760d676,
	0xea23f0af, 0xeee2ed18, 0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
	0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662,
	0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
	0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
};

static inline u32 dvb_crc32(u32 crc, u8 *data, u32 len)
{
	/* from libdvbv5 */
	while (len--)
		crc = (crc << 8) ^ CRC_LUT[((crc >> 24) ^ *data++) & 0xff];
	return crc;
}

static void vidtv_psi_update_version_num(struct vidtv_psi_table_header *h)
{
	h->version++;
}

static inline u16 vidtv_psi_sdt_serv_get_desc_loop_len(struct vidtv_psi_table_sdt_service *s)
{
	u16 mask;
	u16 ret;

	mask = GENMASK(11, 0);

	ret = be16_to_cpu(s->bitfield) & mask;
	return ret;
}

static inline u16 vidtv_psi_pmt_stream_get_desc_loop_len(struct vidtv_psi_table_pmt_stream *s)
{
	u16 mask;
	u16 ret;

	mask = GENMASK(9, 0);

	ret = be16_to_cpu(s->bitfield2) & mask;
	return ret;
}

static inline u16 vidtv_psi_pmt_get_desc_loop_len(struct vidtv_psi_table_pmt *p)
{
	u16 mask;
	u16 ret;

	mask = GENMASK(9, 0);

	ret = be16_to_cpu(p->bitfield2) & mask;
	return ret;
}

static inline u16 vidtv_psi_get_sec_len(struct vidtv_psi_table_header *h)
{
	u16 mask;
	u16 ret;

	mask = GENMASK(11, 0);

	ret = be16_to_cpu(h->bitfield) & mask;
	return ret;
}

inline u16 vidtv_psi_get_pat_program_pid(struct vidtv_psi_table_pat_program *p)
{
	u16 mask;
	u16 ret;

	mask = GENMASK(12, 0);

	ret = be16_to_cpu(p->bitfield) & mask;
	return ret;
}

inline u16 vidtv_psi_pmt_stream_get_elem_pid(struct vidtv_psi_table_pmt_stream *s)
{
	u16 mask;
	u16 ret;

	mask = GENMASK(12, 0);

	ret = be16_to_cpu(s->bitfield) & mask;
	return ret;
}

static inline void vidtv_psi_set_desc_loop_len(__be16 *bitfield, u16 new_len, u8 desc_len_nbits)
{
	u16 mask;
	__be16 new;

	mask = GENMASK(15, desc_len_nbits);

	new = cpu_to_be16((be16_to_cpu(*bitfield) & mask) | new_len);
	*bitfield = new;
}

static void vidtv_psi_set_sec_len(struct vidtv_psi_table_header *h, u16 new_len)
{
	u16 old_len = vidtv_psi_get_sec_len(h);
	__be16 new;
	u16 mask;

	mask = GENMASK(15, 13);

	new = cpu_to_be16((be16_to_cpu(h->bitfield) & mask) | new_len);

	if (old_len > MAX_SECTION_LEN)
		pr_warn_ratelimited("section length: %d > %d, old len was %d\n",
				    new_len,
				    MAX_SECTION_LEN,
				    old_len);

	h->bitfield = new;
}

static u32 vidtv_psi_ts_psi_write_into(struct psi_write_args args)
{
	/*
	 * Packetize PSI sections into TS packets:
	 * push a TS header (4bytes) every 184 bytes
	 * manage the continuity_counter
	 * add stuffing (i.e. padding bytes) after the CRC
	 */

	u32 nbytes_past_boundary = (args.dest_offset % TS_PACKET_LEN);
	bool aligned = (nbytes_past_boundary == 0);
	struct vidtv_mpeg_ts ts_header = {};

	/* number of bytes written by this function */
	u32 nbytes = 0;
	/* how much there is left to write */
	u32 remaining_len = args.len;
	/* how much we can be written in this packet */
	u32 payload_write_len = 0;
	/* where we are in the source */
	u32 payload_offset = 0;

	const u16 PAYLOAD_START = args.new_psi_section;

	if (!args.crc && !args.is_crc)
		pr_warn_ratelimited("Missing CRC for chunk\n");

	if (args.crc)
		*args.crc = dvb_crc32(*args.crc, args.from, args.len);

	if (args.new_psi_section && !aligned) {
		pr_warn_ratelimited("Cannot write a new PSI section in a misaligned buffer\n");

		/* forcibly align and hope for the best */
		nbytes += vidtv_memset(args.dest_buf,
				       args.dest_offset + nbytes,
				       args.dest_buf_sz,
				       TS_FILL_BYTE,
				       TS_PACKET_LEN - nbytes_past_boundary);
	}

	while (remaining_len) {
		nbytes_past_boundary = (args.dest_offset + nbytes) % TS_PACKET_LEN;
		aligned = (nbytes_past_boundary == 0);

		if (aligned) {
			/* if at a packet boundary, write a new TS header */
			ts_header.sync_byte = TS_SYNC_BYTE;
			ts_header.bitfield = cpu_to_be16((PAYLOAD_START << 14) | args.pid);
			ts_header.scrambling = 0;
			ts_header.continuity_counter = *args.continuity_counter;
			ts_header.payload = 1;
			/* no adaptation field */
			ts_header.adaptation_field = 0;

			/* copy the header */
			nbytes += vidtv_memcpy(args.dest_buf,
					       args.dest_offset + nbytes,
					       args.dest_buf_sz,
					       &ts_header,
					       sizeof(ts_header));
			/*
			 * This will trigger a discontinuity if the buffer is full,
			 * effectively dropping the packet.
			 */
			vidtv_ts_inc_cc(args.continuity_counter);
		}

		/* write the pointer_field in the first byte of the payload */
		if (args.new_psi_section)
			nbytes += vidtv_memset(args.dest_buf,
					       args.dest_offset + nbytes,
					       args.dest_buf_sz,
					       0x0,
					       1);

		/* write as much of the payload as possible */
		nbytes_past_boundary = (args.dest_offset + nbytes) % TS_PACKET_LEN;
		payload_write_len = min(TS_PACKET_LEN - nbytes_past_boundary, remaining_len);

		nbytes += vidtv_memcpy(args.dest_buf,
				       args.dest_offset + nbytes,
				       args.dest_buf_sz,
				       args.from + payload_offset,
				       payload_write_len);

		/* 'payload_write_len' written from a total of 'len' requested*/
		remaining_len -= payload_write_len;
		payload_offset += payload_write_len;
	}

	/*
	 * fill the rest of the packet if there is any remaining space unused
	 */

	nbytes_past_boundary = (args.dest_offset + nbytes) % TS_PACKET_LEN;

	if (args.is_crc)
		nbytes += vidtv_memset(args.dest_buf,
				       args.dest_offset + nbytes,
				       args.dest_buf_sz,
				       TS_FILL_BYTE,
				       TS_PACKET_LEN - nbytes_past_boundary);

	return nbytes;
}

static u32 table_section_crc32_write_into(struct crc32_write_args args)
{
	/* the CRC is the last entry in the section */
	u32 nbytes = 0;
	struct psi_write_args psi_args = {};

	psi_args.dest_buf           = args.dest_buf;
	psi_args.from               = &args.crc;
	psi_args.len                = CRC_SIZE_IN_BYTES;
	psi_args.dest_offset        = args.dest_offset;
	psi_args.pid                = args.pid;
	psi_args.new_psi_section    = false;
	psi_args.continuity_counter = args.continuity_counter;
	psi_args.is_crc             = true;
	psi_args.dest_buf_sz        = args.dest_buf_sz;

	nbytes += vidtv_psi_ts_psi_write_into(psi_args);

	return nbytes;
}

struct vidtv_psi_desc_service *vidtv_psi_service_desc_init(struct vidtv_psi_desc *head,
							   enum service_type service_type,
							   char *service_name,
							   char *provider_name)
{
	struct vidtv_psi_desc_service *desc;
	u32 service_name_len = service_name ? strlen(service_name) : 0;
	u32 provider_name_len = provider_name ? strlen(provider_name) : 0;

	desc = kzalloc(sizeof(*desc), GFP_KERNEL);

	desc->type = SERVICE_DESCRIPTOR;

	desc->length = sizeof_field(struct vidtv_psi_desc_service, service_type)
		       + sizeof_field(struct vidtv_psi_desc_service, provider_name_len)
		       + provider_name_len
		       + sizeof_field(struct vidtv_psi_desc_service, service_name_len)
		       + service_name_len;

	desc->service_type = service_type;

	desc->service_name_len = service_name_len;

	if (service_name && service_name_len)
		desc->service_name = kstrdup(service_name, GFP_KERNEL);

	desc->provider_name_len = provider_name_len;

	if (provider_name && provider_name_len)
		desc->provider_name = kstrdup(provider_name, GFP_KERNEL);

	if (head) {
		while (head->next)
			head = head->next;

		head->next = (struct vidtv_psi_desc *)desc;
	}
	return desc;
}

struct vidtv_psi_desc_registration
*vidtv_psi_registration_desc_init(struct vidtv_psi_desc *head,
				  __be32 format_id,
				  u8 *additional_ident_info,
				  u32 additional_info_len)
{
	struct vidtv_psi_desc_registration *desc;

	desc = kzalloc(sizeof(*desc) + sizeof(format_id) + additional_info_len, GFP_KERNEL);

	desc->type = REGISTRATION_DESCRIPTOR;

	desc->length = sizeof_field(struct vidtv_psi_desc_registration, format_id)
		       + additional_info_len;

	desc->format_id = format_id;

	if (additional_ident_info && additional_info_len)
		memcpy(desc->additional_identification_info,
		       additional_ident_info,
		       additional_info_len);

	if (head) {
		while (head->next)
			head = head->next;

		head->next = (struct vidtv_psi_desc *)desc;
	}

	return desc;
}

struct vidtv_psi_desc *vidtv_psi_desc_clone(struct vidtv_psi_desc *desc)
{
	struct vidtv_psi_desc *head = NULL;
	struct vidtv_psi_desc *prev = NULL;
	struct vidtv_psi_desc *curr = NULL;

	struct vidtv_psi_desc_service *service;

	while (desc) {
		switch (desc->type) {
		case SERVICE_DESCRIPTOR:
			service = (struct vidtv_psi_desc_service *)desc;
			curr = (struct vidtv_psi_desc *)
				vidtv_psi_service_desc_init(head,
							    service->service_type,
							    service->service_name,
							    service->provider_name);
		break;

		case REGISTRATION_DESCRIPTOR:
		default:
			curr = kzalloc(sizeof(*desc) + desc->length, GFP_KERNEL);
			memcpy(curr, desc, sizeof(*desc) + desc->length);
		break;
	}

		if (curr)
			curr->next = NULL;
		if (!head)
			head = curr;
		if (prev)
			prev->next = curr;

		prev = curr;
		desc = desc->next;
	}

	return head;
}

void vidtv_psi_desc_destroy(struct vidtv_psi_desc *desc)
{
	struct vidtv_psi_desc *curr = desc;
	struct vidtv_psi_desc *tmp  = NULL;

	while (curr) {
		tmp  = curr;
		curr = curr->next;

		switch (tmp->type) {
		case SERVICE_DESCRIPTOR:
			kfree(((struct vidtv_psi_desc_service *)tmp)->provider_name);
			kfree(((struct vidtv_psi_desc_service *)tmp)->service_name);

			break;
		case REGISTRATION_DESCRIPTOR:
			/* nothing to do */
			break;

		default:
			pr_warn_ratelimited("Possible leak: not handling descriptor type %d\n",
					    tmp->type);
			break;
		}

		kfree(tmp);
	}
}

static u16
vidtv_psi_desc_comp_loop_len(struct vidtv_psi_desc *desc)
{
	u32 length = 0;

	if (!desc)
		return 0;

	while (desc) {
		length += sizeof_field(struct vidtv_psi_desc, type);
		length += sizeof_field(struct vidtv_psi_desc, length);
		length += desc->length; /* from 'length' field until the end of the descriptor */
		desc    = desc->next;
	}

	return length;
}

void vidtv_psi_desc_assign(struct vidtv_psi_desc **to,
			   struct vidtv_psi_desc *desc)
{
	if (desc == *to)
		return;

	if (*to)
		vidtv_psi_desc_destroy(*to);

	*to = desc;
}

void vidtv_pmt_desc_assign(struct vidtv_psi_table_pmt *pmt,
			   struct vidtv_psi_desc **to,
			   struct vidtv_psi_desc *desc)
{
	vidtv_psi_desc_assign(to, desc);
	vidtv_psi_pmt_table_update_sec_len(pmt);

	if (vidtv_psi_get_sec_len(&pmt->header) > MAX_SECTION_LEN)
		vidtv_psi_desc_assign(to, NULL);

	vidtv_psi_update_version_num(&pmt->header);
}

void vidtv_sdt_desc_assign(struct vidtv_psi_table_sdt *sdt,
			   struct vidtv_psi_desc **to,
			   struct vidtv_psi_desc *desc)
{
	vidtv_psi_desc_assign(to, desc);
	vidtv_psi_sdt_table_update_sec_len(sdt);

	if (vidtv_psi_get_sec_len(&sdt->header) > MAX_SECTION_LEN)
		vidtv_psi_desc_assign(to, NULL);

	vidtv_psi_update_version_num(&sdt->header);
}

static u32 vidtv_psi_desc_write_into(struct desc_write_args args)
{
	/* the number of bytes written by this function */
	u32 nbytes = 0;
	struct psi_write_args psi_args = {};

	psi_args.dest_buf = args.dest_buf;
	psi_args.from     = &args.desc->type;

	psi_args.len = sizeof_field(struct vidtv_psi_desc, type) +
		       sizeof_field(struct vidtv_psi_desc, length);

	psi_args.dest_offset        = args.dest_offset + nbytes;
	psi_args.pid                = args.pid;
	psi_args.new_psi_section    = false;
	psi_args.continuity_counter = args.continuity_counter;
	psi_args.is_crc             = false;
	psi_args.dest_buf_sz        = args.dest_buf_sz;
	psi_args.crc                = args.crc;

	nbytes += vidtv_psi_ts_psi_write_into(psi_args);

	switch (args.desc->type) {
	case SERVICE_DESCRIPTOR:
		psi_args.dest_offset = args.dest_offset + nbytes;
		psi_args.len = sizeof_field(struct vidtv_psi_desc_service, service_type) +
			       sizeof_field(struct vidtv_psi_desc_service, provider_name_len);
		psi_args.from = &((struct vidtv_psi_desc_service *)args.desc)->service_type;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);

		psi_args.dest_offset = args.dest_offset + nbytes;
		psi_args.len = ((struct vidtv_psi_desc_service *)args.desc)->provider_name_len;
		psi_args.from = ((struct vidtv_psi_desc_service *)args.desc)->provider_name;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);

		psi_args.dest_offset = args.dest_offset + nbytes;
		psi_args.len = sizeof_field(struct vidtv_psi_desc_service, service_name_len);
		psi_args.from = &((struct vidtv_psi_desc_service *)args.desc)->service_name_len;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);

		psi_args.dest_offset = args.dest_offset + nbytes;
		psi_args.len = ((struct vidtv_psi_desc_service *)args.desc)->service_name_len;
		psi_args.from = ((struct vidtv_psi_desc_service *)args.desc)->service_name;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);
		break;

	case REGISTRATION_DESCRIPTOR:
	default:
		psi_args.dest_offset = args.dest_offset + nbytes;
		psi_args.len = args.desc->length;
		psi_args.from = &args.desc->data;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);
		break;
	}

	return nbytes;
}

static u32
vidtv_psi_table_header_write_into(struct header_write_args args)
{
	/* the number of bytes written by this function */
	u32 nbytes = 0;
	struct psi_write_args psi_args = {};

	psi_args.dest_buf           = args.dest_buf;
	psi_args.from               = args.h;
	psi_args.len                = sizeof(struct vidtv_psi_table_header);
	psi_args.dest_offset        = args.dest_offset;
	psi_args.pid                = args.pid;
	psi_args.new_psi_section    = true;
	psi_args.continuity_counter = args.continuity_counter;
	psi_args.is_crc             = false;
	psi_args.dest_buf_sz        = args.dest_buf_sz;
	psi_args.crc                = args.crc;

	nbytes += vidtv_psi_ts_psi_write_into(psi_args);

	return nbytes;
}

void
vidtv_psi_pat_table_update_sec_len(struct vidtv_psi_table_pat *pat)
{
	/* see ISO/IEC 13818-1 : 2000 p.43 */
	u16 length = 0;
	u32 i;

	/* from immediately after 'section_length' until 'last_section_number'*/
	length += PAT_LEN_UNTIL_LAST_SECTION_NUMBER;

	/* do not count the pointer */
	for (i = 0; i < pat->programs; ++i)
		length += sizeof(struct vidtv_psi_table_pat_program) -
			  sizeof(struct vidtv_psi_table_pat_program *);

	length += CRC_SIZE_IN_BYTES;

	vidtv_psi_set_sec_len(&pat->header, length);
}

void vidtv_psi_pmt_table_update_sec_len(struct vidtv_psi_table_pmt *pmt)
{
	/* see ISO/IEC 13818-1 : 2000 p.46 */
	u16 length = 0;
	struct vidtv_psi_table_pmt_stream *s = pmt->stream;
	u16 desc_loop_len;

	/* from immediately after 'section_length' until 'program_info_length'*/
	length += PMT_LEN_UNTIL_PROGRAM_INFO_LENGTH;

	desc_loop_len = vidtv_psi_desc_comp_loop_len(pmt->descriptor);
	vidtv_psi_set_desc_loop_len(&pmt->bitfield2, desc_loop_len, 10);

	length += desc_loop_len;

	while (s) {
		/* skip both pointers at the end */
		length += sizeof(struct vidtv_psi_table_pmt_stream) -
			  sizeof(struct vidtv_psi_desc *) -
			  sizeof(struct vidtv_psi_table_pmt_stream *);

		desc_loop_len = vidtv_psi_desc_comp_loop_len(s->descriptor);
		vidtv_psi_set_desc_loop_len(&s->bitfield2, desc_loop_len, 10);

		length += desc_loop_len;

		s = s->next;
	}

	length += CRC_SIZE_IN_BYTES;

	vidtv_psi_set_sec_len(&pmt->header, length);
}

void vidtv_psi_sdt_table_update_sec_len(struct vidtv_psi_table_sdt *sdt)
{
	/* see ETSI EN 300 468 V 1.10.1 p.24 */
	u16 length = 0;
	struct vidtv_psi_table_sdt_service *s = sdt->service;
	u16 desc_loop_len;

	/*
	 * from immediately after 'section_length' until
	 * 'reserved_for_future_use'
	 */
	length += SDT_LEN_UNTIL_RESERVED_FOR_FUTURE_USE;

	while (s) {
		/* skip both pointers at the end */
		length += sizeof(struct vidtv_psi_table_sdt_service) -
			  sizeof(struct vidtv_psi_desc *) -
			  sizeof(struct vidtv_psi_table_sdt_service *);

		desc_loop_len = vidtv_psi_desc_comp_loop_len(s->descriptor);
		vidtv_psi_set_desc_loop_len(&s->bitfield, desc_loop_len, 12);

		length += desc_loop_len;

		s = s->next;
	}

	length += CRC_SIZE_IN_BYTES;

	vidtv_psi_set_sec_len(&sdt->header, length);
}

struct vidtv_psi_table_pat_program*
vidtv_psi_pat_program_init(struct vidtv_psi_table_pat_program *head,
			   u16 service_id,
			   u16 program_map_pid)
{
	struct vidtv_psi_table_pat_program *program;
	const u16 RESERVED = 0x07;

	program = kzalloc(sizeof(*program), GFP_KERNEL);

	program->service_id = cpu_to_be16(service_id);

	/* pid for the PMT section in the TS */
	program->bitfield = cpu_to_be16((RESERVED << 13) | program_map_pid);
	program->next = NULL;

	if (head) {
		while (head->next)
			head = head->next;

		head->next = program;
	}

	return program;
}

void
vidtv_psi_pat_program_destroy(struct vidtv_psi_table_pat_program *p)
{
	struct vidtv_psi_table_pat_program *curr = p;
	struct vidtv_psi_table_pat_program *tmp  = NULL;

	while (curr) {
		tmp  = curr;
		curr = curr->next;
		kfree(tmp);
	}
}

void
vidtv_psi_pat_program_assign(struct vidtv_psi_table_pat *pat,
			     struct vidtv_psi_table_pat_program *p)
{
	/* This function transfers ownership of p to the table */

	u16 program_count = 0;
	struct vidtv_psi_table_pat_program *program = p;

	if (p == pat->program)
		return;

	while (program) {
		++program_count;
		program = program->next;
	}

	pat->programs = program_count;
	pat->program  = p;

	/* Recompute section length */
	vidtv_psi_pat_table_update_sec_len(pat);

	if (vidtv_psi_get_sec_len(&pat->header) > MAX_SECTION_LEN)
		vidtv_psi_pat_program_assign(pat, NULL);

	vidtv_psi_update_version_num(&pat->header);
}

struct vidtv_psi_table_pat *vidtv_psi_pat_table_init(u16 transport_stream_id)
{
	struct vidtv_psi_table_pat *pat = kzalloc(sizeof(*pat), GFP_KERNEL);
	const u16 SYNTAX = 0x1;
	const u16 ZERO = 0x0;
	const u16 ONES = 0x03;

	pat->header.table_id = 0x0;

	pat->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ZERO << 14) | (ONES << 12));
	pat->header.id           = cpu_to_be16(transport_stream_id);
	pat->header.current_next = 0x1;

	pat->header.version = 0x1f;

	pat->header.one2         = 0x03;
	pat->header.section_id   = 0x0;
	pat->header.last_section = 0x0;

	pat->programs = 0;

	vidtv_psi_pat_table_update_sec_len(pat);

	return pat;
}

u32 vidtv_psi_pat_write_into(struct vidtv_psi_pat_write_args args)
{
	/* the number of bytes written by this function */
	u32 nbytes = 0;
	const u16 pat_pid = VIDTV_PAT_PID;
	u32 crc = 0xffffffff;

	struct vidtv_psi_table_pat_program *p = args.pat->program;

	struct header_write_args h_args       = {};
	struct psi_write_args psi_args            = {};
	struct crc32_write_args c_args        = {};

	vidtv_psi_pat_table_update_sec_len(args.pat);

	h_args.dest_buf           = args.buf;
	h_args.dest_offset        = args.offset;
	h_args.h                  = &args.pat->header;
	h_args.pid                = pat_pid;
	h_args.continuity_counter = args.continuity_counter;
	h_args.dest_buf_sz        = args.buf_sz;
	h_args.crc = &crc;

	nbytes += vidtv_psi_table_header_write_into(h_args);

	/* note that the field 'u16 programs' is not really part of the PAT */

	psi_args.dest_buf           = args.buf;
	psi_args.pid                = pat_pid;
	psi_args.new_psi_section    = false;
	psi_args.continuity_counter = args.continuity_counter;
	psi_args.is_crc             = false;
	psi_args.dest_buf_sz        = args.buf_sz;
	psi_args.crc                = &crc;

	while (p) {
		/* copy the PAT programs */
		psi_args.from = p;
		/* skip the pointer */
		psi_args.len = sizeof(*p) -
			   sizeof(struct vidtv_psi_table_pat_program *);
		psi_args.dest_offset = args.offset + nbytes;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);

		p = p->next;
	}

	c_args.dest_buf           = args.buf;
	c_args.dest_offset        = args.offset + nbytes;
	c_args.crc                = cpu_to_be32(crc);
	c_args.pid                = pat_pid;
	c_args.continuity_counter = args.continuity_counter;
	c_args.dest_buf_sz        = args.buf_sz;

	/* Write the CRC32 at the end */
	nbytes += table_section_crc32_write_into(c_args);

	return nbytes;
}

void
vidtv_psi_pat_table_destroy(struct vidtv_psi_table_pat *p)
{
	vidtv_psi_pat_program_destroy(p->program);
	kfree(p);
}

struct vidtv_psi_table_pmt_stream*
vidtv_psi_pmt_stream_init(struct vidtv_psi_table_pmt_stream *head,
			  enum vidtv_psi_stream_types stream_type,
			  u16 es_pid)
{
	struct vidtv_psi_table_pmt_stream *stream;
	const u16 RESERVED1 = 0x07;
	const u16 RESERVED2 = 0x0f;
	const u16 ZERO = 0x0;
	u16 desc_loop_len;

	stream = kzalloc(sizeof(*stream), GFP_KERNEL);

	stream->type = stream_type;

	stream->bitfield = cpu_to_be16((RESERVED1 << 13) | es_pid);

	desc_loop_len = vidtv_psi_desc_comp_loop_len(stream->descriptor);

	stream->bitfield2 = cpu_to_be16((RESERVED2 << 12) |
					(ZERO << 10)      |
					desc_loop_len);
	stream->next = NULL;

	if (head) {
		while (head->next)
			head = head->next;

		head->next = stream;
	}

	return stream;
}

void vidtv_psi_pmt_stream_destroy(struct vidtv_psi_table_pmt_stream *s)
{
	struct vidtv_psi_table_pmt_stream *curr_stream = s;
	struct vidtv_psi_table_pmt_stream *tmp_stream  = NULL;

	while (curr_stream) {
		tmp_stream  = curr_stream;
		curr_stream = curr_stream->next;
		vidtv_psi_desc_destroy(tmp_stream->descriptor);
		kfree(tmp_stream);
	}
}

void vidtv_psi_pmt_stream_assign(struct vidtv_psi_table_pmt *pmt,
				 struct vidtv_psi_table_pmt_stream *s)
{
	/* This function transfers ownership of s to the table */
	if (s == pmt->stream)
		return;

	pmt->stream = s;
	vidtv_psi_pmt_table_update_sec_len(pmt);

	if (vidtv_psi_get_sec_len(&pmt->header) > MAX_SECTION_LEN)
		vidtv_psi_pmt_stream_assign(pmt, NULL);

	vidtv_psi_update_version_num(&pmt->header);
}

u16 vidtv_psi_pmt_get_pid(struct vidtv_psi_table_pmt *section,
			  struct vidtv_psi_table_pat *pat)
{
	struct vidtv_psi_table_pat_program *program = pat->program;

	/*
	 * service_id is the same as program_number in the
	 * corresponding program_map_section
	 * see ETSI EN 300 468 v1.15.1 p. 24
	 */
	while (program) {
		if (program->service_id == section->header.id)
			return vidtv_psi_get_pat_program_pid(program);

		program = program->next;
	}

	return TS_LAST_VALID_PID + 1; /* not found */
}

struct vidtv_psi_table_pmt *vidtv_psi_pmt_table_init(u16 program_number,
						     u16 pcr_pid)
{
	struct vidtv_psi_table_pmt *pmt = kzalloc(sizeof(*pmt), GFP_KERNEL);
	const u16 SYNTAX = 0x1;
	const u16 ZERO = 0x0;
	const u16 ONES = 0x03;
	const u16 RESERVED1 = 0x07;
	const u16 RESERVED2 = 0x0f;
	u16 desc_loop_len;

	if (!pcr_pid)
		pcr_pid = 0x1fff;

	pmt->header.table_id = 0x2;

	pmt->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ZERO << 14) | (ONES << 12));

	pmt->header.id = cpu_to_be16(program_number);
	pmt->header.current_next = 0x1;

	pmt->header.version = 0x1f;

	pmt->header.one2 = ONES;
	pmt->header.section_id   = 0;
	pmt->header.last_section = 0;

	pmt->bitfield = cpu_to_be16((RESERVED1 << 13) | pcr_pid);

	desc_loop_len = vidtv_psi_desc_comp_loop_len(pmt->descriptor);

	pmt->bitfield2 = cpu_to_be16((RESERVED2 << 12) |
				     (ZERO << 10)      |
				     desc_loop_len);

	vidtv_psi_pmt_table_update_sec_len(pmt);

	return pmt;
}

u32 vidtv_psi_pmt_write_into(struct vidtv_psi_pmt_write_args args)
{
	/* the number of bytes written by this function */
	u32 nbytes = 0;
	u32 crc = 0xffffffff;

	struct vidtv_psi_desc *table_descriptor   = args.pmt->descriptor;
	struct vidtv_psi_table_pmt_stream *stream = args.pmt->stream;
	struct vidtv_psi_desc *stream_descriptor  = (stream) ?
						    args.pmt->stream->descriptor :
						    NULL;

	struct header_write_args h_args = {};
	struct psi_write_args psi_args  = {};
	struct desc_write_args d_args   = {};
	struct crc32_write_args c_args  = {};

	vidtv_psi_pmt_table_update_sec_len(args.pmt);

	h_args.dest_buf           = args.buf;
	h_args.dest_offset        = args.offset;
	h_args.h                  = &args.pmt->header;
	h_args.pid                = args.pid;
	h_args.continuity_counter = args.continuity_counter;
	h_args.dest_buf_sz        = args.buf_sz;
	h_args.crc                = &crc;

	nbytes += vidtv_psi_table_header_write_into(h_args);

	/* write the two bitfields */
	psi_args.dest_buf = args.buf;
	psi_args.from     = &args.pmt->bitfield;
	psi_args.len      = sizeof_field(struct vidtv_psi_table_pmt, bitfield) +
			    sizeof_field(struct vidtv_psi_table_pmt, bitfield2);

	psi_args.dest_offset        = args.offset + nbytes;
	psi_args.pid                = args.pid;
	psi_args.new_psi_section    = false;
	psi_args.continuity_counter = args.continuity_counter;
	psi_args.is_crc             = false;
	psi_args.dest_buf_sz        = args.buf_sz;
	psi_args.crc                = &crc;

	nbytes += vidtv_psi_ts_psi_write_into(psi_args);

	while (table_descriptor) {
		/* write the descriptors, if any */
		d_args.dest_buf           = args.buf;
		d_args.dest_offset        = args.offset + nbytes;
		d_args.desc               = table_descriptor;
		d_args.pid                = args.pid;
		d_args.continuity_counter = args.continuity_counter;
		d_args.dest_buf_sz        = args.buf_sz;
		d_args.crc                = &crc;

		nbytes += vidtv_psi_desc_write_into(d_args);

		table_descriptor = table_descriptor->next;
	}

	while (stream) {
		/* write the streams, if any */
		psi_args.from = stream;
		psi_args.len  = sizeof_field(struct vidtv_psi_table_pmt_stream, type) +
				sizeof_field(struct vidtv_psi_table_pmt_stream, bitfield) +
				sizeof_field(struct vidtv_psi_table_pmt_stream, bitfield2);
		psi_args.dest_offset = args.offset + nbytes;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);

		while (stream_descriptor) {
			/* write the stream descriptors, if any */
			d_args.dest_buf           = args.buf;
			d_args.dest_offset        = args.offset + nbytes;
			d_args.desc               = stream_descriptor;
			d_args.pid                = args.pid;
			d_args.continuity_counter = args.continuity_counter;
			d_args.dest_buf_sz        = args.buf_sz;
			d_args.crc                = &crc;

			nbytes += vidtv_psi_desc_write_into(d_args);

			stream_descriptor = stream_descriptor->next;
		}

		stream = stream->next;
	}

	c_args.dest_buf           = args.buf;
	c_args.dest_offset        = args.offset + nbytes;
	c_args.crc                = cpu_to_be32(crc);
	c_args.pid                = args.pid;
	c_args.continuity_counter = args.continuity_counter;
	c_args.dest_buf_sz        = args.buf_sz;

	/* Write the CRC32 at the end */
	nbytes += table_section_crc32_write_into(c_args);

	return nbytes;
}

void vidtv_psi_pmt_table_destroy(struct vidtv_psi_table_pmt *pmt)
{
	vidtv_psi_desc_destroy(pmt->descriptor);
	vidtv_psi_pmt_stream_destroy(pmt->stream);
	kfree(pmt);
}

struct vidtv_psi_table_sdt *vidtv_psi_sdt_table_init(u16 transport_stream_id)
{
	struct vidtv_psi_table_sdt *sdt = kzalloc(sizeof(*sdt), GFP_KERNEL);
	const u16 SYNTAX = 0x1;
	const u16 ONE = 0x1;
	const u16 ONES = 0x03;
	const u16 RESERVED = 0xff;

	sdt->header.table_id = 0x42;

	sdt->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ONE << 14) | (ONES << 12));

	/*
	 * This is a 16-bit field which serves as a label for identification
	 * of the TS, about which the SDT informs, from any other multiplex
	 * within the delivery system.
	 */
	sdt->header.id = cpu_to_be16(transport_stream_id);
	sdt->header.current_next = ONE;

	sdt->header.version = 0x1f;

	sdt->header.one2  = ONES;
	sdt->header.section_id   = 0;
	sdt->header.last_section = 0;

	/*
	 * FIXME: The network_id range from 0xFF01 to 0xFFFF is used to
	 * indicate temporary private use. For now, let's use the first
	 * value.
	 * This can be changed to something more useful, when support for
	 * NIT gets added
	 */
	sdt->network_id = cpu_to_be16(0xff01);
	sdt->reserved = RESERVED;

	vidtv_psi_sdt_table_update_sec_len(sdt);

	return sdt;
}

u32 vidtv_psi_sdt_write_into(struct vidtv_psi_sdt_write_args args)
{
	u32 nbytes  = 0;
	u16 sdt_pid = VIDTV_SDT_PID;  /* see ETSI EN 300 468 v1.15.1 p. 11 */

	u32 crc = 0xffffffff;

	struct vidtv_psi_table_sdt_service *service = args.sdt->service;
	struct vidtv_psi_desc *service_desc = (args.sdt->service) ?
					      args.sdt->service->descriptor :
					      NULL;

	struct header_write_args h_args = {};
	struct psi_write_args psi_args  = {};
	struct desc_write_args d_args   = {};
	struct crc32_write_args c_args  = {};

	vidtv_psi_sdt_table_update_sec_len(args.sdt);

	h_args.dest_buf           = args.buf;
	h_args.dest_offset        = args.offset;
	h_args.h                  = &args.sdt->header;
	h_args.pid                = sdt_pid;
	h_args.continuity_counter = args.continuity_counter;
	h_args.dest_buf_sz        = args.buf_sz;
	h_args.crc                = &crc;

	nbytes += vidtv_psi_table_header_write_into(h_args);

	psi_args.dest_buf = args.buf;
	psi_args.from     = &args.sdt->network_id;

	psi_args.len = sizeof_field(struct vidtv_psi_table_sdt, network_id) +
		       sizeof_field(struct vidtv_psi_table_sdt, reserved);

	psi_args.dest_offset        = args.offset + nbytes;
	psi_args.pid                = sdt_pid;
	psi_args.new_psi_section    = false;
	psi_args.continuity_counter = args.continuity_counter;
	psi_args.is_crc             = false;
	psi_args.dest_buf_sz        = args.buf_sz;
	psi_args.crc                = &crc;

	/* copy u16 network_id + u8 reserved)*/
	nbytes += vidtv_psi_ts_psi_write_into(psi_args);

	while (service) {
		/* copy the services, if any */
		psi_args.from = service;
		/* skip both pointers at the end */
		psi_args.len = sizeof(struct vidtv_psi_table_sdt_service) -
			       sizeof(struct vidtv_psi_desc *) -
			       sizeof(struct vidtv_psi_table_sdt_service *);
		psi_args.dest_offset = args.offset + nbytes;

		nbytes += vidtv_psi_ts_psi_write_into(psi_args);

		while (service_desc) {
			/* copy the service descriptors, if any */
			d_args.dest_buf           = args.buf;
			d_args.dest_offset        = args.offset + nbytes;
			d_args.desc               = service_desc;
			d_args.pid                = sdt_pid;
			d_args.continuity_counter = args.continuity_counter;
			d_args.dest_buf_sz        = args.buf_sz;
			d_args.crc                = &crc;

			nbytes += vidtv_psi_desc_write_into(d_args);

			service_desc = service_desc->next;
		}

		service = service->next;
	}

	c_args.dest_buf           = args.buf;
	c_args.dest_offset        = args.offset + nbytes;
	c_args.crc                = cpu_to_be32(crc);
	c_args.pid                = sdt_pid;
	c_args.continuity_counter = args.continuity_counter;
	c_args.dest_buf_sz        = args.buf_sz;

	/* Write the CRC at the end */
	nbytes += table_section_crc32_write_into(c_args);

	return nbytes;
}

void vidtv_psi_sdt_table_destroy(struct vidtv_psi_table_sdt *sdt)
{
	vidtv_psi_sdt_service_destroy(sdt->service);
	kfree(sdt);
}

struct vidtv_psi_table_sdt_service
*vidtv_psi_sdt_service_init(struct vidtv_psi_table_sdt_service *head,
			    u16 service_id)
{
	struct vidtv_psi_table_sdt_service *service;

	service = kzalloc(sizeof(*service), GFP_KERNEL);

	/*
	 * ETSI 300 468: this is a 16bit field which serves as a label to
	 * identify this service from any other service within the TS.
	 * The service id is the same as the program number in the
	 * corresponding program_map_section
	 */
	service->service_id            = cpu_to_be16(service_id);
	service->EIT_schedule          = 0x0;
	service->EIT_present_following = 0x0;
	service->reserved              = 0x3f;

	service->bitfield = cpu_to_be16(RUNNING << 13);

	if (head) {
		while (head->next)
			head = head->next;

		head->next = service;
	}

	return service;
}

void
vidtv_psi_sdt_service_destroy(struct vidtv_psi_table_sdt_service *service)
{
	struct vidtv_psi_table_sdt_service *curr = service;
	struct vidtv_psi_table_sdt_service *tmp  = NULL;

	while (curr) {
		tmp  = curr;
		curr = curr->next;
		vidtv_psi_desc_destroy(tmp->descriptor);
		kfree(tmp);
	}
}

void
vidtv_psi_sdt_service_assign(struct vidtv_psi_table_sdt *sdt,
			     struct vidtv_psi_table_sdt_service *service)
{
	if (service == sdt->service)
		return;

	sdt->service = service;

	/* recompute section length */
	vidtv_psi_sdt_table_update_sec_len(sdt);

	if (vidtv_psi_get_sec_len(&sdt->header) > MAX_SECTION_LEN)
		vidtv_psi_sdt_service_assign(sdt, NULL);

	vidtv_psi_update_version_num(&sdt->header);
}

struct vidtv_psi_table_pmt**
vidtv_psi_pmt_create_sec_for_each_pat_entry(struct vidtv_psi_table_pat *pat, u16 pcr_pid)

{
	/*
	 * PMTs contain information about programs. For each program,
	 * there is one PMT section. This function will create a section
	 * for each program found in the PAT
	 */
	struct vidtv_psi_table_pat_program *program = pat->program;
	struct vidtv_psi_table_pmt **pmt_secs;
	u32 i = 0;

	/* a section for each program_id */
	pmt_secs = kcalloc(pat->programs,
			   sizeof(struct vidtv_psi_table_pmt *),
			   GFP_KERNEL);

	while (program) {
		pmt_secs[i] = vidtv_psi_pmt_table_init(be16_to_cpu(program->service_id), pcr_pid);
		++i;
		program = program->next;
	}

	return pmt_secs;
}

struct vidtv_psi_table_pmt
*vidtv_psi_find_pmt_sec(struct vidtv_psi_table_pmt **pmt_sections,
			u16 nsections,
			u16 program_num)
{
	/* find the PMT section associated with 'program_num' */
	struct vidtv_psi_table_pmt *sec = NULL;
	u32 i;

	for (i = 0; i < nsections; ++i) {
		sec = pmt_sections[i];
		if (be16_to_cpu(sec->header.id) == program_num)
			return sec;
	}

	return NULL; /* not found */
}