[uClinux-dev] Problem with mmap(0, MAP_SHARED, PROT_READ|PROT_WRITE) on /dev/fb

Matthias Welwarsky matze at stud.fbi.fh-darmstadt.de
Fri Aug 23 05:10:48 EDT 2002


there is a certain problem with mmaping the framebuffer memory. On uClinux, 
this is quite simple, the mmap call just needs to return the start address of 
the framebuffer, however, checks in mmnommu/mmap.c/do_mmap_pgoff prohibit 
that you can map a file MAP_SHARED and PROT_WRITE. This may be valid for 
regular files, but it is not valid for device nodes.

So, is it possible to only prohibit MAP_SHARED/PROT_WRITE on regular files? 
Right now I have to hack Qt/Embedded to get it working, and I'd rather not do 
this :)


Matthias Welwarsky
Fachschaft Informatik FH Darmstadt
Email: matze at stud.fbi.fh-darmstadt.de

"all software sucks equally, but some software is more equal"
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