Re: [PATCH v2 fbdev-for-next 1/2] fbcon: introduce for_each_registered_fb() helper

[Jani Nikula]

On Sat, 30 Jun 2018, Yisheng Xie <ysxie@xxxxxxxxxxx> wrote:
> Following pattern is often used:
>
>  for (i = 0; i < FB_MAX; i++) {
>         if (registered_fb[i]) {
>                 ...
>         }
>  }
>
> Therefore, as Andy's suggestion, for_each_registered_fb() helper can
> be introduced to make the code easier to read and write by reducing
> indentation level. It also saves few lines of code in each occurrence.
>
> This patch convert all part here at the same time.
>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Yisheng Xie <ysxie@xxxxxxxxxxx>
> ---
> v2:
>  - rebase it to fbdev-for-next branch and add one more loop to replace - per Hans
>  - Macro should be protected against nested conditionals. - per Andy
>  drivers/video/fbdev/core/fbcon.c | 31 +++++++++++--------------------
>  drivers/video/fbdev/core/fbmem.c |  4 +---
>  include/linux/fb.h               |  4 ++++
>  3 files changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 5fb156b..e30d3a1 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -2234,8 +2234,8 @@ static int fbcon_switch(struct vc_data *vc)
>  	 *
>  	 * info->currcon = vc->vc_num;
>  	 */
> -	for (i = 0; i < FB_MAX; i++) {
> -		if (registered_fb[i] != NULL && registered_fb[i]->fbcon_par) {
> +	for_each_registered_fb(i) {
> +		if (registered_fb[i]->fbcon_par) {
>  			struct fbcon_ops *o = registered_fb[i]->fbcon_par;
>  
>  			o->currcon = vc->vc_num;
> @@ -3124,11 +3124,9 @@ static int fbcon_fb_unregistered(struct fb_info *info)
>  	if (idx == info_idx) {
>  		info_idx = -1;
>  
> -		for (i = 0; i < FB_MAX; i++) {
> -			if (registered_fb[i] != NULL) {
> -				info_idx = i;
> -				break;
> -			}
> +		for_each_registered_fb(i) {
> +			info_idx = i;
> +			break;
>  		}
>  	}
>  
> @@ -3609,10 +3607,8 @@ static int fbcon_output_notifier(struct notifier_block *nb,
>  	deferred_takeover = false;
>  	logo_shown = FBCON_LOGO_DONTSHOW;
>  
> -	for (i = 0; i < FB_MAX; i++) {
> -		if (registered_fb[i])
> -			fbcon_fb_registered(registered_fb[i]);
> -	}
> +	for_each_registered_fb(i)
> +		fbcon_fb_registered(registered_fb[i]);
>  
>  	return NOTIFY_OK;
>  }
> @@ -3638,11 +3634,9 @@ static void fbcon_start(void)
>  
>  		console_lock();
>  
> -		for (i = 0; i < FB_MAX; i++) {
> -			if (registered_fb[i] != NULL) {
> -				info_idx = i;
> -				break;
> -			}
> +		for_each_registered_fb(i) {
> +			info_idx = i;
> +			break;
>  		}
>  
>  		do_fbcon_takeover(0);
> @@ -3669,15 +3663,12 @@ static void fbcon_exit(void)
>  	kfree((void *)softback_buf);
>  	softback_buf = 0UL;
>  
> -	for (i = 0; i < FB_MAX; i++) {
> +	for_each_registered_fb(i) {
>  		int pending = 0;
>  
>  		mapped = 0;
>  		info = registered_fb[i];
>  
> -		if (info == NULL)
> -			continue;
> -
>  		if (info->queue.func)
>  			pending = cancel_work_sync(&info->queue);
>  		DPRINTK("fbcon: %s pending work\n", (pending ? "canceled" :
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 609438d..645c6ac 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1593,10 +1593,8 @@ static int do_remove_conflicting_framebuffers(struct apertures_struct *a,
>  	int i, ret;
>  
>  	/* check all firmware fbs and kick off if the base addr overlaps */
> -	for (i = 0 ; i < FB_MAX; i++) {
> +	for_each_registered_fb(i) {
>  		struct apertures_struct *gen_aper;
> -		if (!registered_fb[i])
> -			continue;
>  
>  		if (!(registered_fb[i]->flags & FBINFO_MISC_FIRMWARE))
>  			continue;
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index aa74a22..fd31e6f 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -650,6 +650,10 @@ extern int fb_get_color_depth(struct fb_var_screeninfo *var,
>  extern int num_registered_fb;
>  extern struct class *fb_class;
>  
> +#define for_each_registered_fb(i)		\
> +	for (i = 0; i < FB_MAX; i++)		\
> +		if (!registered_fb[i]) {} else

There's for_each_if in drmP.h to handle dangling else. Maybe that should
be lifted outside of drm.

BR,
Jani.

> +
>  extern int lock_fb_info(struct fb_info *info);
>  
>  static inline void unlock_fb_info(struct fb_info *info)

-- 
Jani Nikula, Intel Open Source Graphics Center