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.
...
quoted hunk ↗ jump to hunk
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