Re: [PATCH v2 09/19] fbcon: Extract fbcon_open/release helpers

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 08.02.22 um 22:08 schrieb Daniel Vetter:
> There's two minor behaviour changes in here:
> - in error paths we now consistently call fb_ops->fb_release
> - fb_release really can't fail (fbmem.c ignores it too) and there's no
>    reasonable cleanup we can do anyway.
> 
> Note that everything in fbcon.c is protected by the big console_lock()
> lock (especially all the global variables), so the minor changes in
> ordering of setup/cleanup do not matter.
> 
> v2: Explain a bit better why this is all correct (Sam)
> 
> Acked-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Claudio Suarez <cssk@net-c.es>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Du Cheng <ducheng2@gmail.com>
> ---
>   drivers/video/fbdev/core/fbcon.c | 107 +++++++++++++++----------------
>   1 file changed, 53 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 058e885d24f6..3e1a3e7bf527 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -682,19 +682,37 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
>   
>   #endif /* CONFIG_MISC_TILEBLITTING */
>   
> +static int fbcon_open(struct fb_info *info)
> +{
> +	if (!try_module_get(info->fbops->owner))
> +		return -ENODEV;
> +
> +	if (info->fbops->fb_open &&
> +	    info->fbops->fb_open(info, 0)) {
> +		module_put(info->fbops->owner);
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static void fbcon_release(struct fb_info *info)
> +{
> +	if (info->fbops->fb_release)
> +		info->fbops->fb_release(info, 0);
> +
> +	module_put(info->fbops->owner);
> +}
>   
>   static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
>   				  int unit, int oldidx)
>   {
>   	struct fbcon_ops *ops = NULL;
> -	int err = 0;
> -
> -	if (!try_module_get(info->fbops->owner))
> -		err = -ENODEV;
> +	int err;
>   
> -	if (!err && info->fbops->fb_open &&
> -	    info->fbops->fb_open(info, 0))
> -		err = -ENODEV;
> +	err = fbcon_open(info);
> +	if (err)
> +		return err;
>   
>   	if (!err) {
>   		ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> @@ -715,7 +733,7 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
>   
>   	if (err) {
>   		con2fb_map[unit] = oldidx;
> -		module_put(info->fbops->owner);
> +		fbcon_release(info);
>   	}
>   
>   	return err;
> @@ -726,45 +744,34 @@ static int con2fb_release_oldinfo(struct vc_data *vc, struct fb_info *oldinfo,
>   				  int oldidx, int found)
>   {
>   	struct fbcon_ops *ops = oldinfo->fbcon_par;
> -	int err = 0, ret;
> +	int ret;
>   
> -	if (oldinfo->fbops->fb_release &&
> -	    oldinfo->fbops->fb_release(oldinfo, 0)) {
> -		con2fb_map[unit] = oldidx;

We don't need oldidx any longer?

There's some logic wrt to the parameter 'found' here and in 
set_con2fb_map() that appears to be relevant.

Best regards
Thomas


> -		if (!found && newinfo->fbops->fb_release)
> -			newinfo->fbops->fb_release(newinfo, 0);
> -		if (!found)
> -			module_put(newinfo->fbops->owner);
> -		err = -ENODEV;
> -	}
> +	fbcon_release(oldinfo);
>   
> -	if (!err) {
> -		fbcon_del_cursor_work(oldinfo);
> -		kfree(ops->cursor_state.mask);
> -		kfree(ops->cursor_data);
> -		kfree(ops->cursor_src);
> -		kfree(ops->fontbuffer);
> -		kfree(oldinfo->fbcon_par);
> -		oldinfo->fbcon_par = NULL;
> -		module_put(oldinfo->fbops->owner);
> -		/*
> -		  If oldinfo and newinfo are driving the same hardware,
> -		  the fb_release() method of oldinfo may attempt to
> -		  restore the hardware state.  This will leave the
> -		  newinfo in an undefined state. Thus, a call to
> -		  fb_set_par() may be needed for the newinfo.
> -		*/
> -		if (newinfo && newinfo->fbops->fb_set_par) {
> -			ret = newinfo->fbops->fb_set_par(newinfo);
> +	fbcon_del_cursor_work(oldinfo);
> +	kfree(ops->cursor_state.mask);
> +	kfree(ops->cursor_data);
> +	kfree(ops->cursor_src);
> +	kfree(ops->fontbuffer);
> +	kfree(oldinfo->fbcon_par);
> +	oldinfo->fbcon_par = NULL;
> +	/*
> +	  If oldinfo and newinfo are driving the same hardware,
> +	  the fb_release() method of oldinfo may attempt to
> +	  restore the hardware state.  This will leave the
> +	  newinfo in an undefined state. Thus, a call to
> +	  fb_set_par() may be needed for the newinfo.
> +	*/
> +	if (newinfo && newinfo->fbops->fb_set_par) {
> +		ret = newinfo->fbops->fb_set_par(newinfo);
>   
> -			if (ret)
> -				printk(KERN_ERR "con2fb_release_oldinfo: "
> -					"detected unhandled fb_set_par error, "
> -					"error code %d\n", ret);
> -		}
> +		if (ret)
> +			printk(KERN_ERR "con2fb_release_oldinfo: "
> +				"detected unhandled fb_set_par error, "
> +				"error code %d\n", ret);
>   	}
>   
> -	return err;
> +	return 0;
>   }
>   
>   static void con2fb_init_display(struct vc_data *vc, struct fb_info *info,
> @@ -919,7 +926,6 @@ static const char *fbcon_startup(void)
>   	struct fbcon_display *p = &fb_display[fg_console];
>   	struct vc_data *vc = vc_cons[fg_console].d;
>   	const struct font_desc *font = NULL;
> -	struct module *owner;
>   	struct fb_info *info = NULL;
>   	struct fbcon_ops *ops;
>   	int rows, cols;
> @@ -938,17 +944,12 @@ static const char *fbcon_startup(void)
>   	if (!info)
>   		return NULL;
>   	
> -	owner = info->fbops->owner;
> -	if (!try_module_get(owner))
> +	if (fbcon_open(info))
>   		return NULL;
> -	if (info->fbops->fb_open && info->fbops->fb_open(info, 0)) {
> -		module_put(owner);
> -		return NULL;
> -	}
>   
>   	ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
>   	if (!ops) {
> -		module_put(owner);
> +		fbcon_release(info);
>   		return NULL;
>   	}
>   
> @@ -3314,10 +3315,6 @@ static void fbcon_exit(void)
>   		}
>   
>   		if (mapped) {
> -			if (info->fbops->fb_release)
> -				info->fbops->fb_release(info, 0);
> -			module_put(info->fbops->owner);
> -
>   			if (info->fbcon_par) {
>   				struct fbcon_ops *ops = info->fbcon_par;
>   
> @@ -3327,6 +3324,8 @@ static void fbcon_exit(void)
>   				kfree(info->fbcon_par);
>   				info->fbcon_par = NULL;
>   			}
> +
> +			fbcon_release(info);
>   		}
>   	}
>   }

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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