RTEMS MAP_SHARED support expansion

[Kirspel, Kevin]

I would like to expand support for MAP_SHARED in mmap().  I would like to run a few ideas by the group to see which direction to go.  I really only need to expand MAP_SHARED support for some LIBBSD drivers that I want to create.  There are two approaches I can take.

The first approach is to just add a mmap handler function in "struct _rtems_filesystem_file_handlers_r".  The mmap() restrictions on MAP_SHARED would be removed.  The mmap handler for all RTEMS file systems (except SHM) would get the default mmap handler (return EINVAL).  SHM would get a handler similar to the one found in mmap.c.  In RTEMS-LIBBSD, the RTEMS character device handler (devfs_devs.c) would be free to pass the mmap request on to FREEBSD drivers.

The second approach includes the first approach but adds support for RTEMS device drivers.  We would need to add a mmap handler to "rtems_driver_address_table".  The "IMFS_device_handlers" would add a mmap handler to device_mmap().  We would need a new rtems_deviceio_mmap() function to call the drivers mmap handler.  I don't think any BSPs will be affected because the mmap handler of "rtems_driver_address_table" should initialize to NULL.  Any BSP would them be free to add a handler to process mmap calls.

Any opposition to the two approaches?  If not, which one would you prefer?

Kevin Kirspel
Electrical Engineer - Sr. Staff
Idexx Roswell
235 Hembree Park Drive
Roswell GA 30076
Tel: (770)-510-4444 ext. 81642
Direct: (770)-688-1642
Fax: (770)-510-4445

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