test-drivers/vidtv/vidtv_common.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * The Virtual DVB test driver serves as a reference DVB driver and helps
0004  * validate the existing APIs in the media subsystem. It can also aid
0005  * developers working on userspace applications.
0006  *
0007  * Copyright (C) 2020 Daniel W. S. Almeida
0008  */
0009 #define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
0010
0011 #include <linux/printk.h>
0012 #include <linux/ratelimit.h>
0013 #include <linux/string.h>
0014 #include <linux/types.h>
0015
0016 #include "vidtv_common.h"
0017
0018 /**
0019  * vidtv_memcpy() - wrapper routine to be used by MPEG-TS
0020  *  generator, in order to avoid going past the
0021  *  output buffer.
0022  * @to: Starting element to where a MPEG-TS packet will
0023  *  be copied.
0024  * @to_offset:  Starting position of the @to buffer to be filled.
0025  * @to_size:    Size of the @to buffer.
0026  * @from:   Starting element of the buffer to be copied.
0027  * @len:    Number of elements to be copy from @from buffer
0028  *  into @to+ @to_offset buffer.
0029  *
0030  * Note:
0031  *  Real digital TV demod drivers should not have memcpy
0032  *  wrappers. We use it here because emulating MPEG-TS
0033  *  generation at kernelspace requires some extra care.
0034  *
0035  * Return:
0036  *  Returns the number of bytes written
0037  */
0038 u32 vidtv_memcpy(void *to,
0039          size_t to_offset,
0040          size_t to_size,
0041          const void *from,
0042          size_t len)
0043 {
0044     if (unlikely(to_offset + len > to_size)) {
0045         pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size. Needed %zu, had %zu\n",
0046                    to_offset + len,
0047                    to_size);
0048         return 0;
0049     }
0050
0051     memcpy(to + to_offset, from, len);
0052     return len;
0053 }
0054
0055 /**
0056  * vidtv_memset() - wrapper routine to be used by MPEG-TS
0057  *  generator, in order to avoid going past the
0058  *  output buffer.
0059  * @to: Starting element to set
0060  * @to_offset:  Starting position of the @to buffer to be filled.
0061  * @to_size:    Size of the @to buffer.
0062  * @c:      The value to set the memory to.
0063  * @len:    Number of elements to be copy from @from buffer
0064  *  into @to+ @to_offset buffer.
0065  *
0066  * Note:
0067  *  Real digital TV demod drivers should not have memset
0068  *  wrappers. We use it here because emulating MPEG-TS
0069  *  generation at kernelspace requires some extra care.
0070  *
0071  * Return:
0072  *  Returns the number of bytes written
0073  */
0074 u32 vidtv_memset(void *to,
0075          size_t to_offset,
0076          size_t to_size,
0077          const int c,
0078          size_t len)
0079 {
0080     if (unlikely(to_offset + len > to_size)) {
0081         pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size. Needed %zu, had %zu\n",
0082                    to_offset + len,
0083                    to_size);
0084         return 0;
0085     }
0086
0087     memset(to + to_offset, c, len);
0088     return len;
0089 }