1 | @c |
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2 | @c COPYRIGHT (c) 1988-1998. |
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3 | @c On-Line Applications Research Corporation (OAR). |
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4 | @c All rights reserved. |
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5 | @c |
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6 | @c $Id$ |
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7 | @c |
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8 | |
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9 | @chapter Miscellaneous Support Files |
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10 | |
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11 | @section GCC Compiler Specifications File |
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12 | |
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13 | The file @code{bsp_specs} defines the start files and libraries |
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14 | that are always used with this BSP. The format of this file |
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15 | is admittedly cryptic and this document will make no attempt |
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16 | to explain it completely. Below is the @code{bsp_specs} |
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17 | file from the PowerPC psim BSP: |
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18 | |
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19 | @example |
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20 | @group |
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21 | %rename cpp old_cpp |
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22 | %rename lib old_lib |
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23 | %rename endfile old_endfile |
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24 | %rename startfile old_startfile |
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25 | %rename link old_link |
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26 | |
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27 | *cpp: |
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28 | %(old_cpp) %@{qrtems: -D__embedded__@} -Asystem(embedded) |
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29 | |
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30 | *lib: |
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31 | %@{!qrtems: %(old_lib)@} %@{qrtems: --start-group \ |
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32 | %@{!qrtems_debug: -lrtemsall@} %@{qrtems_debug: -lrtemsall_g@} \ |
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33 | -lc -lgcc --end-group ecrtn%O%s \ |
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34 | %@{!qnolinkcmds: -T linkcmds%s@}@} |
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35 | |
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36 | *startfile: |
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37 | %@{!qrtems: %(old_startfile)@} %@{qrtems: ecrti%O%s \ |
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38 | %@{!qrtems_debug: startsim.o%s@} \ |
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39 | %@{qrtems_debug: startsim_g.o%s@}@} |
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40 | |
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41 | *link: |
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42 | %@{!qrtems: %(old_link)@} %@{qrtems: -Qy -dp -Bstatic \ |
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43 | -T linkcmds%s -e _start -u __vectors@} |
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44 | @end group |
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45 | @end example |
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46 | |
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47 | The first section of this file renames the built-in definition of |
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48 | some specification variables so they can be augmented without |
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49 | embedded their original definition. The subsequent sections |
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50 | specify what behavior is expected when the @code{-qrtems} or |
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51 | @code{-qrtems_debug} option is specified. |
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52 | |
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53 | The @code{*cpp} definition specifies that when @code{-qrtems} |
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54 | is specified, predefine the preprocessor symbol @code{__embedded__}. |
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55 | |
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56 | The @code{*lib} section insures that the RTEMS library, BSP specific |
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57 | linker script, gcc support library, and the EABI specific @code{ecrtn} |
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58 | file are used. |
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59 | |
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60 | The @code{*startfile} section specifies that the BSP specific file |
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61 | @code{startsim.o} will be used instead of @code{crt0.o}. In addition, |
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62 | the EABI specific file @code{ecrti.o} will be linked in with the |
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63 | executable. |
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64 | |
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65 | The @code{*link} section specifies the arguments that will be passed to |
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66 | the linker. |
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67 | |
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68 | The format of this file is specific to the GNU Compiler Suite. The |
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69 | argument used to override and extend the compiler built-in specifications |
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70 | is relatively new to the toolset. The @code{-specs} option is present |
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71 | in all @code{egcs} distributions and @code{gcc} distributions starting |
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72 | with version 2.8.0. |
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73 | |
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74 | @section README Files |
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75 | |
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76 | Most BSPs provide one or more @code{README} files. Generally, there |
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77 | is a @code{README} file at the top of the BSP source. This file |
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78 | describes the board and its hardware configuration, provides vendor |
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79 | information, local configuration information, information on downloading |
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80 | code to the board, debugging, etc.. The intent of this |
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81 | file is to help someone begin to use the BSP faster. |
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82 | |
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83 | A @code{README} file in a BSP subdirectory typically explains something |
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84 | about the contents of that subdirectory in greater detail. For example, |
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85 | it may list the documentation available for a particular peripheral |
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86 | controller and how to obtain that documentation. It may also explain some |
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87 | particularly cryptic part of the software in that directory or provide |
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88 | rationale on the implementation. |
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89 | |
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90 | @section times |
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91 | |
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92 | This file contains the results of the RTEMS Timing Test Suite. It is |
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93 | in a standard format so that results from one BSP can be easily compared |
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94 | with those of another target board. |
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95 | |
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96 | If a BSP supports multiple variants, then there may be multiple @code{times} |
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97 | files. Usually these are named @code{times.VARIANTn}. |
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98 | |
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99 | @section Tools Subdirectory |
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100 | |
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101 | Some BSPs provide additional tools that aid in using the target board. |
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102 | These tools run on the development host and are built as part of building |
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103 | the BSP. Most common is a script to automate running the RTEMS Test Suites |
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104 | on the BSP. Examples of this include: |
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105 | |
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106 | @itemize @bullet |
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107 | |
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108 | @item @code{powerpc/psim} includes scripts to ease use of the simulator |
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109 | |
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110 | @item @code{m68k/mvme162} includes a utility to download across the |
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111 | VMEbus into target memory if the host is a VMEbus board in the same |
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112 | chasis. |
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113 | |
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114 | @item @code{unix/posix} includes scripts to run the tests automatically |
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115 | on this BSP. |
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116 | |
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117 | @end itemize |
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118 | |
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119 | @section bsp.h Include File |
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120 | |
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121 | The file @code{include/bsp.h} contains prototypes and definitions |
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122 | specific to this board. Every BSP is required to provide a @code{bsp.h}. |
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123 | The best approach to writing a @code{bsp.h} is copying an existing one |
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124 | as a starting point. |
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125 | |
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126 | Many @code{bsp.h} files provide prototypes of variables defined |
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127 | in the linker script (@code{linkcmds}). |
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128 | |
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129 | There are a number of fields in this file that are used only by the |
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130 | RTEMS Test Suites. The following is a list of these: |
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131 | |
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132 | @itemize @bullet |
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133 | @item @code{MAX_LONG_TEST_DURATION} - the longest length of time a |
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134 | "long running" test should run. |
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135 | |
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136 | @item @code{MAX_SHORT_TEST_DURATION} - the longest length of time a |
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137 | "short running" test should run. |
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138 | |
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139 | @item @code{MUST_WAIT_FOR_INTERRUPT} - modifies behavior of @code{tm27}. |
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140 | |
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141 | @item @code{Install_tm27_vector} - installs the interrupt service |
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142 | routine for the Interrupt Benchmark Test (@code{tm27}). |
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143 | |
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144 | @item @code{Cause_tm27_intr} - generates the interrupt source |
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145 | used in the Interrupt Benchmark Test (@code{tm27}). |
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146 | |
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147 | @item @code{Clear_tm27_intr} - clears the interrupt source |
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148 | used in the Interrupt Benchmark Test (@code{tm27}). |
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149 | |
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150 | @item @code{Lower_tm27_intr} - lowers the interrupt mask so the |
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151 | interrupt source used in the Interrupt Benchmark Test (@code{tm27}) |
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152 | can generate a nested interrupt. |
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153 | |
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154 | @end itemize |
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155 | |
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156 | @section Calling Overhead File |
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157 | |
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158 | The file @code{include/coverhd.h} contains the overhead associated |
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159 | with invoking each directive. This overhead consists of the execution |
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160 | time required to package the parameters as well as to execute the "jump to |
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161 | subroutine" and "return from subroutine" sequence. The intent of this |
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162 | file is to help separate the calling overhead from the actual execution |
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163 | time of a directive. This file is only used by the tests in the |
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164 | RTEMS Timing Test Suite. |
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165 | |
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166 | The numbers in this file are obtained by running the "Timer Overhead" |
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167 | @code{tmoverhd} test. The numbers in this file may be 0 and no |
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168 | overhead is subtracted from the directive execution times reported by |
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169 | the Timing Suite. |
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170 | |
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171 | @section sbrk() Implementation |
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172 | |
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173 | If the BSP wants to dynamically extend the heap used by the |
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174 | C Library memory allocation routines (i.e. @code{malloc} family), |
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175 | then this routine must be functional. The following is the |
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176 | prototype for this routine: |
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177 | |
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178 | @example |
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179 | void * sbrk(size_t increment) |
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180 | @end example |
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181 | |
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182 | The @code{increment} amount is based upon the @code{sbrk_amount} |
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183 | parameter passed to the @code{RTEMS_Malloc_Initialize} during system |
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184 | initialization. |
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185 | See @ref{Initialization Code RTEMS Pretasking Callback} for more |
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186 | information. |
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187 | |
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188 | There is a default implementation which returns an error to indicate |
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189 | that the heap can not be extended. This implementation can be |
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190 | found in @code{c/src/lib/libbsp/shared/sbrk.c}. Many of the BSPs |
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191 | use this shared implementation. In order to use this implementation, |
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192 | the file @code{Makefile.in} in the BSP's @code{startup} directory |
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193 | must be modified so that the @code{$VPATH} variable searches |
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194 | both the @code{startup} directory and the shared directory. The following |
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195 | illustates the @code{VPATH} setting in the PowerPC psim BSP's |
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196 | @code{startup/Makefile.in}: |
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197 | |
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198 | @example |
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199 | VPATH = @@srcdir@@:@@srcdir@@/../../../shared |
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200 | @end example |
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201 | |
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202 | This instructs make to look in all of the directories in the @code{VPATH} |
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203 | for the source files. The directories will be examined in the order |
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204 | they are specified. |
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205 | |
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206 | @section bsp_cleanup() - Cleanup the Hardware |
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207 | |
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208 | The @code{bsp_cleanup()} is the last C code invoked. Most of the BSPs |
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209 | use the same shared version of @code{bsp_cleanup()} that does nothing. |
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210 | This implementation is located in the following file: |
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211 | |
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212 | @example |
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213 | c/src/lib/libbsp/shared/bspclean.c |
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214 | @end example |
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215 | |
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216 | The @code{bsp_cleanup()} routine can be used to return to a ROM monitor, |
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217 | insure that interrupt sources are disabled, etc.. This routine is the |
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218 | last place to insure a clean shutdown of the hardware. |
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219 | |
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220 | @section set_vector() - Install an Interrupt Vector |
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221 | |
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222 | The @code{set_vector} routine is responsible for installing an interrupt |
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223 | vector. It invokes the support routines necessary to install an |
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224 | interrupt handler as either a "raw" or an RTEMS interrupt handler. Raw |
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225 | handlers bypass the RTEMS interrupt structure and are responsible for |
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226 | saving and restoring all their own registers. Raw handlers are useful |
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227 | for handling traps, debug vectors, etc.. |
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228 | |
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229 | The @code{set_vector} routine is a central place to perform |
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230 | interrupt controller manipulation and encapsulate that information. |
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231 | It is usually implemented as follows: |
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232 | |
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233 | @example |
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234 | @group |
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235 | rtems_isr_entry set_vector( /* returns old vector */ |
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236 | rtems_isr_entry handler, /* isr routine */ |
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237 | rtems_vector_number vector, /* vector number */ |
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238 | int type /* RTEMS or RAW intr */ |
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239 | ) |
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240 | @{ |
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241 | if the type is RAW |
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242 | install the raw vector |
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243 | else |
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244 | use rtems_interrupt_catch to install the vector |
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245 | |
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246 | perform any interrupt controller necessary to unmask |
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247 | the interrupt source |
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248 | |
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249 | return the previous handler |
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250 | @} |
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251 | @end group |
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252 | @end example |
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253 | |
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254 | |
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255 | @b{NOTE:} @code{set_vector} is provided by the majority of BSPs but |
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256 | not all. In particular, the i386 BSPs use a different scheme. |
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257 | |
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