README
1 OPERATING SYSTEM SPECIFIC MIPS MSA DETECTION
2 --------------------------------------------
3
4 Detection of the ability to execute MIPS MSA on an MIPS processor requires
5 operating system support. (The information is not available in user mode.)
6
7 HOW TO USE THIS
8 ---------------
9
10 This directory contains C code fragments that can be included in mips/mips_init.c
11 by setting the macro PNG_MIPS_MSA_FILE to the file name in "" or <> at build
12 time. This setting is not recorded in pnglibconf.h and can be changed simply by
13 rebuilding mips/msa_init.o with the required macro definition.
14
15 For any of this code to be used the MIPS MSA code must be enabled and run time
16 checks must be supported. I.e.:
17
18 #if PNG_MIPS_MSA_OPT > 0
19 #ifdef PNG_MIPS_MSA_CHECK_SUPPORTED
20
21 This is done in a 'configure' build by passing configure the argument:
22
23 --enable-mips-msa=check
24
25 Apart from the basic Linux implementation in contrib/mips-msa/linux.c this code
26 is unsupported. That means that it is not even compiled on a regular basis and
27 may be broken in any given minor release.
28
29 FILE FORMAT
30 -----------
31
32 Each file documents its testing status as of the last time it was tested (which
33 may have been a long time ago):
34
35 STATUS: one of:
36 SUPPORTED: This indicates that the file is included in the regularly
37 performed test builds and bugs are fixed when discovered.
38 COMPILED: This indicates that the code did compile at least once. See the
39 more detailed description for the extent to which the result was
40 successful.
41 TESTED: This means the code was fully compiled into the libpng test programs
42 and these were run at least once.
43
44 BUG REPORTS: an email address to which to send reports of problems
45
46 The file is a fragment of C code. It should not define any 'extern' symbols;
47 everything should be static. It must define the function:
48
49 static int png_have_msa(png_structp png_ptr);
50
51 That function must return 1 if MIPS MSA instructions are supported, 0 if not.
52 It must not execute png_error unless it detects a bug. A png_error will prevent
53 the reading of the PNG and in the future, writing too.
54
55 BUG REPORTS
56 -----------
57
58 If you mail a bug report for any file that is not SUPPORTED there may only be
59 limited response. Consider fixing it and sending a patch to fix the problem -
60 this is more likely to result in action.
61
62 CONTRIBUTIONS
63 -------------
64
65 You may send contributions of new implementations to
66 png-mng-implement (a] sourceforge.net. Please write code in strict C90 C where
67 possible. Obviously OS dependencies are to be expected. If you submit code you
68 must have the authors permission and it must have a license that is acceptable
69 to the current maintainer; in particular that license must permit modification
70 and redistribution.
71
72 Please try to make the contribution a single file and give the file a clear and
73 unambiguous name that identifies the target OS. If multiple files really are
74 required put them all in a sub-directory.
75
76 You must also be prepared to handle bug reports from users of the code, either
77 by joining the png-mng-implement mailing list or by providing an email for the
78 "BUG REPORTS" entry or both. Please make sure that the header of the file
79 contains the STATUS and BUG REPORTS fields as above.
80
81 Please list the OS requirements as precisely as possible. Ideally you should
82 also list the environment in which the code has been tested and certainly list
83 any environments where you suspect it might not work.
84