OpenWrt Forum Archive

Topic: /dev/fb0 framebuffer size limited to 512KB

The content of this topic has been archived on 2 May 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

Recently I find a weird issue, when I use simple framebuffer driver in openwrt(latest version and old version), if I only do read, its size is normal 1152000 bytes, but if I use any write command, for example cp dat /dev/fb0, it will report not enough space(dat is 1.152MB) and then if I read from that fb0, its size is truncated to 512KB.

In my ubuntu system do not have such  issue. So I guess there might be some limit openwrt do to the kernel?
Please help me. smile

Do you use the "old" framebuffer API or the modern
DRM framebuffer ??

with my FL2000 USB3 device I can allocate around
3 MByte (1376 * 768)
more is maybe useable, but currently I have other issues to solve.
https://github.com/FrescoLogic/FL2000/issues/12

elektroman wrote:

Do you use the "old" framebuffer API or the modern
DRM framebuffer ??

with my FL2000 USB3 device I can allocate around
3 MByte (1376 * 768)
more is maybe useable, but currently I have other issues to solve.
https://github.com/FrescoLogic/FL2000/issues/12

Thank you for reply!
I have solved the issue, it is because simple frame buffer is not a memory frame buffer, so actually I write to address 0xa0000000 which is the cpu register...cause the problem. I guess I have to write one "memory" frame buffer smile

The discussion might have continued from here.