drivers/media/test-drivers/vidtv/vidtv_common.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * The Virtual DVB test driver serves as a reference DVB driver and helps
   4  * validate the existing APIs in the media subsystem. It can also aid
   5  * developers working on userspace applications.
   6  *
   7  * Copyright (C) 2020 Daniel W. S. Almeida
   8  */
   9 #define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
  10
  11 #include <linux/printk.h>
  12 #include <linux/ratelimit.h>
  13 #include <linux/string.h>
  14 #include <linux/types.h>
  15
  16 #include "vidtv_common.h"
  17
  18 /**
  19  * vidtv_memcpy() - wrapper routine to be used by MPEG-TS
  20  *      generator, in order to avoid going past the
  21  *      output buffer.
  22  * @to: Starting element to where a MPEG-TS packet will
  23  *      be copied.
  24  * @to_offset:  Starting position of the @to buffer to be filled.
  25  * @to_size:    Size of the @to buffer.
  26  * @from:       Starting element of the buffer to be copied.
  27  * @len:        Number of elements to be copy from @from buffer
  28  *      into @to+ @to_offset buffer.
  29  *
  30  * Note:
  31  *      Real digital TV demod drivers should not have memcpy
  32  *      wrappers. We use it here because emulating MPEG-TS
  33  *      generation at kernelspace requires some extra care.
  34  *
  35  * Return:
  36  *      Returns the number of bytes written
  37  */
  38 u32 vidtv_memcpy(void *to,
  39                  size_t to_offset,
  40                  size_t to_size,
  41                  const void *from,
  42                  size_t len)
  43 {
  44         if (unlikely(to_offset + len > to_size)) {
  45                 pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size. Needed %zu, had %zu\n",
  46                                    to_offset + len,
  47                                    to_size);
  48                 return 0;
  49         }
  50
  51         memcpy(to + to_offset, from, len);
  52         return len;
  53 }
  54
  55 /**
  56  * vidtv_memset() - wrapper routine to be used by MPEG-TS
  57  *      generator, in order to avoid going past the
  58  *      output buffer.
  59  * @to: Starting element to set
  60  * @to_offset:  Starting position of the @to buffer to be filled.
  61  * @to_size:    Size of the @to buffer.
  62  * @c:          The value to set the memory to.
  63  * @len:        Number of elements to be copy from @from buffer
  64  *      into @to+ @to_offset buffer.
  65  *
  66  * Note:
  67  *      Real digital TV demod drivers should not have memset
  68  *      wrappers. We use it here because emulating MPEG-TS
  69  *      generation at kernelspace requires some extra care.
  70  *
  71  * Return:
  72  *      Returns the number of bytes written
  73  */
  74 u32 vidtv_memset(void *to,
  75                  size_t to_offset,
  76                  size_t to_size,
  77                  const int c,
  78                  size_t len)
  79 {
  80         if (unlikely(to_offset + len > to_size)) {
  81                 pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size. Needed %zu, had %zu\n",
  82                                    to_offset + len,
  83                                    to_size);
  84                 return 0;
  85         }
  86
  87         memset(to + to_offset, c, len);
  88         return len;
  89 }