On Wed, Apr 5, 2023, at 17:05, Thomas Zimmermann wrote:
Generic implementations of fb_pgprotect() and fb_is_primary_device()
have been in the source code for a long time. Prepare the header file
to make use of them.
Improve the code by using an inline function for fb_pgprotect() and
by removing include statements.
Symbols are protected by preprocessor guards. Architectures that
provide a symbol need to define a preprocessor token of the same
name and value. Otherwise the header file will provide a generic
implementation. This pattern has been taken from <asm/io.h>.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Moving this into generic code is good, but I'm not sure
about the default for fb_pgprotect():
+
+#ifndef fb_pgprotect
+#define fb_pgprotect fb_pgprotect
+static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
+ unsigned long off)
+{ }
+#endif
I think most architectures will want the version we have on
arc, arm, arm64, loongarch, and sh already:
static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
unsigned long off)
{
vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
}
so I'd suggest making that version the default, and treating the
empty ones (m68knommu, sparc32) as architecture specific
workarounds.
I see that sparc64 and parisc use pgprot_uncached here, but as
they don't define a custom pgprot_writecombine, this ends up being
the same, and they can use the above definition as well.
mips defines pgprot_writecombine but uses pgprot_noncached
in fb_pgprotect(), which is probably a mistake and should have
been updated as part of commit 4b050ba7a66c ("MIPS: pgtable.h:
Implement the pgprot_writecombine function for MIPS").
Arnd
