Hi Thomas, On Tue, May 02, 2023 at 03:02:21PM +0200, Thomas Zimmermann wrote: > Fbdev's main header file, <linux/fb.h>, includes <asm/io.h> to get > declarations for I/O helper functions. From these declarations, it > later defines framebuffer I/O helpers, such as fb_{read,write}[bwlq]() > or fb_memset(). > > The framebuffer I/O helpers depend on the system architecture and > will therefore be moved into <asm/fb.h>. Prepare this change by first > adding an include statement for <linux/io.h> to <asm-generic/fb.h>. > Include <asm/fb.h> in all source files that use the framebuffer I/O > helpers, so that they still get the necessary I/O functions. > ... > > diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c > index 60a96fdb5dd8..fd38e8a073b8 100644 > --- a/drivers/video/fbdev/arkfb.c > +++ b/drivers/video/fbdev/arkfb.c > @@ -27,6 +27,8 @@ > #include <linux/console.h> /* Why should fb driver call console functions? because console_lock() */ > #include <video/vga.h> > > +#include <asm/fb.h> When we have a header like linux/fb.h - it is my understanding that it is preferred to include that file, and not the asm/fb.h variant. This is assuming the linux/fb.h contains the generic stuff, and includes asm/fb.h for the architecture specific parts. So drivers will include linux/fb.h and then they automatically get the architecture specific parts from asm/fb.h. In other words, drivers are not supposed to include asm/fb.h, if linux.fb.h exists - and linux/fb.h shall include the asm/fb.h. If the above holds true, then it is wrong and not needed to add asm/fb.h as seen above. There are countless examples where the above are not followed, but to my best understanding the above it the preferred way to do it. Sam