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 }
90