Hi Javier, On Thu, Feb 24, 2022 at 10:02:59AM +0100, Javier Martinez Canillas wrote:
Hello Sam,
On 2/23/22 21:25, Sam Ravnborg wrote:
[snip]
Question: What is cfb an abbreviation for anyway? Not related to the patch - but if I have known the memory is lost..
I was curious so I dug on this. It seems CFB stands for Color Frame Buffer. Doing a `git grep "(CFB)"` in the linux history repo [0], I get this:
Documentation/isdn/README.diversion: (CFB). drivers/video/pmag-ba-fb.c: * PMAG-BA TURBOchannel Color Frame Buffer (CFB) card support, include/video/pmag-ba-fb.h: * TURBOchannel PMAG-BA Color Frame Buffer (CFB) card support,
Probably the helpers are called like this because they were for any fbdev driver but assumed that the framebuffer was always in I/O memory. Later some drivers were allocating the framebuffer in system memory and still using the helpers, that were using I/O memory accessors and it's ilegal on some arches.
So the sys_* variants where introduced by commit 68648ed1f58d ("fbdev: add drawing functions for framebuffers in system RAM") to fix this. The old ones just kept their name, but probably it should had been renamed to io_* for the naming to be consistent with the sys_* functions.
Interesting - thanks for the history lesson and thanks for taking your time to share your findings too.
Sam