| Leon Scroggins III | 3cc83ac | 2017-10-06 11:02:56 -0400 | [diff] [blame] | 1 | OPERATING SYSTEM SPECIFIC POWERPC DETECTION |
| 2 | -------------------------------------------- |
| 3 | |
| 4 | Detection of the ability to execute POWERPC on processor requires |
| 5 | operating system support. (The information is not available in user mode.) |
| 6 | |
| 7 | Currently only this feature is supported only for linux platform. |
| 8 | |
| 9 | HOW TO USE THIS |
| 10 | --------------- |
| 11 | |
| 12 | This directory contains C code fragments that can be included in powerpc/powerpc_init.c |
| 13 | by setting the macro PNG_POWERPC_VSX_FILE to the file name in "" or <> at build |
| 14 | time. This setting is not recorded in pnglibconf.h and can be changed simply by |
| 15 | rebuilding arm/arm_init.o with the required macro definition. |
| 16 | |
| 17 | For any of this code to be used the POWERPC code must be enabled and run time |
| 18 | checks must be supported. I.e.: |
| 19 | |
| 20 | #if PNG_POWERPC_VSX_OPT > 0 |
| 21 | #ifdef PNG_POWERPC_VSX_CHECK_SUPPORTED |
| 22 | |
| 23 | This is done in a 'configure' build by passing configure the argument: |
| 24 | |
| 25 | --enable-powerpc-vsx=check |
| 26 | |
| 27 | FILE FORMAT |
| 28 | ----------- |
| 29 | |
| 30 | Each file documents its testing status as of the last time it was tested (which |
| 31 | may have been a long time ago): |
| 32 | |
| 33 | STATUS: one of: |
| 34 | SUPPORTED: This indicates that the file is included in the regularly |
| 35 | performed test builds and bugs are fixed when discovered. |
| 36 | COMPILED: This indicates that the code did compile at least once. See the |
| 37 | more detailed description for the extent to which the result was |
| 38 | successful. |
| 39 | TESTED: This means the code was fully compiled into the libpng test programs |
| 40 | and these were run at least once. |
| 41 | |
| 42 | BUG REPORTS: an email address to which to send reports of problems |
| 43 | |
| 44 | The file is a fragment of C code. It should not define any 'extern' symbols; |
| 45 | everything should be static. It must define the function: |
| 46 | |
| 47 | static int png_have_vsx(png_structp png_ptr); |
| 48 | |
| 49 | That function must return 1 if ARM NEON instructions are supported, 0 if not. |
| 50 | It must not execute png_error unless it detects a bug. A png_error will prevent |
| 51 | the reading of the PNG and in the future, writing too. |
| 52 | |
| 53 | BUG REPORTS |
| 54 | ----------- |
| 55 | |
| 56 | If you mail a bug report for any file that is not SUPPORTED there may only be |
| 57 | limited response. Consider fixing it and sending a patch to fix the problem - |
| 58 | this is more likely to result in action. |
| 59 | |
| 60 | CONTRIBUTIONS |
| 61 | ------------- |
| 62 | |
| 63 | You may send contributions of new implementations to |
| 64 | png-mng-implement@sourceforge.net. Please write code in strict C90 C where |
| 65 | possible. Obviously OS dependencies are to be expected. If you submit code you |
| 66 | must have the authors permission and it must have a license that is acceptable |
| 67 | to the current maintainer; in particular that license must permit modification |
| 68 | and redistribution. |
| 69 | |
| 70 | Please try to make the contribution a single file and give the file a clear and |
| 71 | unambiguous name that identifies the target OS. If multiple files really are |
| 72 | required put them all in a sub-directory. |
| 73 | |
| 74 | You must also be prepared to handle bug reports from users of the code, either |
| 75 | by joining the png-mng-implement mailing list or by providing an email for the |
| 76 | "BUG REPORTS" entry or both. Please make sure that the header of the file |
| 77 | contains the STATUS and BUG REPORTS fields as above. |
| 78 | |
| 79 | Please list the OS requirements as precisely as possible. Ideally you should |
| 80 | also list the environment in which the code has been tested and certainly list |
| 81 | any environments where you suspect it might not work. |