Re: [RFC 30/32] /dev/port: don't compile file operations without CONFIG_DEVPORT

Greg Kroah-Hartman
2021-12-28T08:17:46Z

On Mon, Dec 27, 2021 at 05:43:15PM +0100, Niklas Schnelle wrote:
> In the future inb() and friends will not be available when compiling
> with CONFIG_HAS_IOPORT=n so we must only try to access them here if
> CONFIG_DEVPORT is set which depends on HAS_IOPORT.
>
> Co-developed-by: Arnd Bergmann <arnd@kernel.org>
> Signed-off-by: Arnd Bergmann <arnd@kernel.org>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
> drivers/char/mem.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index cc296f0823bd..c1373617153f 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -402,6 +402,7 @@ static int mmap_mem(struct file *file, struct vm_area_struct *vma)
> return 0;
> }
>
> +#ifdef CONFIG_DEVPORT
> static ssize_t read_port(struct file *file, char __user *buf,
> size_t count, loff_t *ppos)
> {
> @@ -443,6 +444,7 @@ static ssize_t write_port(struct file *file, const char __user *buf,
> *ppos = i;
> return tmp-buf;
> }
> +#endif
>
> static ssize_t read_null(struct file *file, char __user *buf,
> size_t count, loff_t *ppos)
> @@ -665,12 +667,14 @@ static const struct file_operations null_fops = {
> .splice_write = splice_write_null,
> };
>
> -static const struct file_operations __maybe_unused port_fops = {
> +#ifdef CONFIG_DEVPORT
> +static const struct file_operations port_fops = {
> .llseek = memory_lseek,
> .read = read_port,
> .write = write_port,
> .open = open_port,
> };
> +#endif

Why is this #ifdef needed if it is already __maybe_unused?

In looking closer, this change could be taken now as the use of this
variable already is behind this same #ifdef statement, right?

thanks,

greg k-h