> On Fri, Jun 10, 2022 at 02:25:18AM -0700, Wang Wenhu wrote: 
> > It is recommended in the "Conditional Compilation" chapter of kernel 
> > coding-style documentation that preprocessor conditionals should not 
> > be used in .c files wherever possible. 
> > 
> > As for the micro CONFIG_HAVE_IOREMAP_PROT, now it's a proper chance 
> > to eliminate it in .c files as we add a no-op function defination 
> > in the header file if the micro is not enabled. 
> > 
> > The main trigger for this patch is an UIO driver series and as Greg 
> > commented we'd better not use such preprocessor contionals. 
> > See: https://lore.kernel.org/lkml/YqHy1uXwCLlJmftr@kroah.com/ 
> > For there is little work to do with the UIO driver, I try to push 
> > this commit independently. 
> > 
> > Signed-off-by: Wang Wenhu <lonehugo@hotmail.com> 
> > --- 
> >  drivers/char/mem.c          | 2 -- 
> >  drivers/fpga/dfl-afu-main.c | 2 -- 
> >  drivers/pci/mmap.c          | 2 -- 
> >  drivers/uio/uio.c           | 2 -- 
> >  include/linux/mm.h          | 8 ++++++++ 
> >  mm/memory.c                 | 4 ---- 
> >  6 files changed, 8 insertions(+), 12 deletions(-) 
> > 
> > diff --git a/drivers/char/mem.c b/drivers/char/mem.c 
> > index 84ca98ed1dad..40186a441e38 100644 
> > --- a/drivers/char/mem.c 
> > +++ b/drivers/char/mem.c 
> > @@ -354,9 +354,7 @@ static inline int private_mapping_ok(struct vm_area_struct *vma) 
> >  #endif 
> >  
> >  static const struct vm_operations_struct mmap_mem_ops = { 
> > -#ifdef CONFIG_HAVE_IOREMAP_PROT 
> >  .access = generic_access_phys 
> > -#endif 
> >  }; 
> >  
> >  static int mmap_mem(struct file *file, struct vm_area_struct *vma) 
> > diff --git a/drivers/fpga/dfl-afu-main.c b/drivers/fpga/dfl-afu-main.c 
> > index 7f621e96d3b8..833e14806c7a 100644 
> > --- a/drivers/fpga/dfl-afu-main.c 
> > +++ b/drivers/fpga/dfl-afu-main.c 
> > @@ -797,9 +797,7 @@ static long afu_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 
> >  } 
> >  
> >  static const struct vm_operations_struct afu_vma_ops = { 
> > -#ifdef CONFIG_HAVE_IOREMAP_PROT 
> >  .access = generic_access_phys, 
> > -#endif 
> >  }; 
> >  
> >  static int afu_mmap(struct file *filp, struct vm_area_struct *vma) 
> > diff --git a/drivers/pci/mmap.c b/drivers/pci/mmap.c 
> > index b8c9011987f4..1dcfabf80453 100644 
> > --- a/drivers/pci/mmap.c 
> > +++ b/drivers/pci/mmap.c 
> > @@ -35,9 +35,7 @@ int pci_mmap_page_range(struct pci_dev *pdev, int bar, 
> >  #endif 
> >  
> >  static const struct vm_operations_struct pci_phys_vm_ops = { 
> > -#ifdef CONFIG_HAVE_IOREMAP_PROT 
> >  .access = generic_access_phys, 
> > -#endif 
> >  }; 
> >  
> >  int pci_mmap_resource_range(struct pci_dev *pdev, int bar, 
> > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c 
> > index 43afbb7c5ab9..c9205a121007 100644 
> > --- a/drivers/uio/uio.c 
> > +++ b/drivers/uio/uio.c 
> > @@ -719,9 +719,7 @@ static int uio_mmap_logical(struct vm_area_struct *vma) 
> >  } 
> >  
> >  static const struct vm_operations_struct uio_physical_vm_ops = { 
> > -#ifdef CONFIG_HAVE_IOREMAP_PROT 
> >  .access = generic_access_phys, 
> > -#endif 
> >  }; 
> >  
> >  static int uio_mmap_physical(struct vm_area_struct *vma) 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h 
> > index bc8f326be0ce..66d0cff6054e 100644 
> > --- a/include/linux/mm.h 
> > +++ b/include/linux/mm.h 
> > @@ -1857,8 +1857,16 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, 
> >  unsigned long *pfn); 
> >  int follow_phys(struct vm_area_struct *vma, unsigned long address, 
> >  unsigned int flags, unsigned long *prot, resource_size_t *phys); 
> > +#ifdef CONFIG_HAVE_IOREMAP_PROT 
> >  int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, 
> >  void *buf, int len, int write); 
> > +#else 
> > +int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, 
> > + void *buf, int len, int write) 
>
> This needs to be an inline function, right? 
>
> Did you test build this? 
>
> thanks, 
>
> greg k-h 
Surely it should have been static inline orelse undefine error happens.
I tested with the micro enabled on ppc, and disabled on arm64,
but I missed up configurations on arm testing code that it's still on.
I will re-confirm it and update the patch later.

thanks,
Wenhu