Re: [PATCH 13/21] fbcon: move more common code into fb_open()

[Daniel Vetter]

On Fri, Feb 04, 2022 at 08:35:31PM +0100, Sam Ravnborg wrote:
> On Mon, Jan 31, 2022 at 10:05:44PM +0100, Daniel Vetter wrote:
> > No idea why con2fb_acquire_newinfo() initializes much less than
> > fbcon_startup(), but so be it. From a quick look most of the
> > un-initialized stuff should be fairly harmless, but who knows.
> > 
> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > Cc: Claudio Suarez <cssk@xxxxxxxx>
> > Cc: Du Cheng <ducheng2@xxxxxxxxx>
> > ---
> >  drivers/video/fbdev/core/fbcon.c | 74 +++++++++++++-------------------
> >  1 file changed, 31 insertions(+), 43 deletions(-)
> > 
> > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > index b83a5a77d8a8..5a3391ff038d 100644
> > --- a/drivers/video/fbdev/core/fbcon.c
> > +++ b/drivers/video/fbdev/core/fbcon.c
> > @@ -680,8 +680,18 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
> >  
> >  #endif /* CONFIG_MISC_TILEBLITTING */
> >  
> > +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 fbcon_open(struct fb_info *info)
> >  {
> > +	struct fbcon_ops *ops;
> > +
> >  	if (!try_module_get(info->fbops->owner))
> >  		return -ENODEV;
> >  
> > @@ -691,19 +701,22 @@ static int fbcon_open(struct fb_info *info)
> >  		return -ENODEV;
> >  	}
> >  
> > -	return 0;
> > -}
> > +	ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> > +	if (!ops) {
> > +		fbcon_release(info);
> > +		return -ENOMEM;
> > +	}
> >  
> > -static void fbcon_release(struct fb_info *info)
> > -{
> > -	if (info->fbops->fb_release)
> > -		info->fbops->fb_release(info, 0);
> > +	INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
> > +	ops->info = info;
> > +	info->fbcon_par = ops;
> > +	ops->cur_blink_jiffies = HZ / 5;
> >  
> > -	module_put(info->fbops->owner);
> > +	return 0;
> >  }
> >  
> >  static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> > -				  int unit, int oldidx)
> > +				  int unit)
> >  {
> >  	struct fbcon_ops *ops = NULL;
> >  	int err;
> > @@ -712,27 +725,10 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> >  	if (err)
> >  		return err;
> >  
> > -	if (!err) {
> > -		ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> > -		if (!ops)
> > -			err = -ENOMEM;
> > -
> > -		INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
> > -	}
> > -
> > -	if (!err) {
> > -		ops->cur_blink_jiffies = HZ / 5;
> > -		ops->info = info;
> > -		info->fbcon_par = ops;
> > -
> > -		if (vc)
> > -			set_blitting_type(vc, info);
> > -	}
> > +	ops = info->fbcon_par;
> >  
> > -	if (err) {
> > -		con2fb_map[unit] = oldidx;
> > -		fbcon_release(info);
> > -	}
> > +	if (vc)
> > +		set_blitting_type(vc, info);
> >  
> >  	return err;
> >  }
> > @@ -840,9 +836,11 @@ static int set_con2fb_map(int unit, int newidx, int user)
> >  
> >  	found = search_fb_in_map(newidx);
> >  
> > -	con2fb_map[unit] = newidx;
> > -	if (!err && !found)
> > -		err = con2fb_acquire_newinfo(vc, info, unit, oldidx);
> > +	if (!err && !found) {
> > +		err = con2fb_acquire_newinfo(vc, info, unit);
> > +		if (!err)
> > +			con2fb_map[unit] = newidx;
> > +	}
> This looks like an unintentional change of functionality as con2fb_map[unit] is
> only assigned when we do a con2fb_acquire_newinfo().
> 
> Staring at the code I could not say it is wrong, but not nice to hide
> the change in this patch.

Nope, it's not an unintentional bugfix. The old con2fb_acquire_newinfo did
reset con2fb_map to oldidx upon failure, which I've found to be a most
bizarre calling convention. So this sorts this out.

The reason I smashed this into the same patch is that I had to remove the
fbcon_release call, and so the error handling in there looked even more
funny. But I indeed failed to explain this all in the commit message.

Ack with that explainer, or do you want me to split this out properly?
-Daniel

> 
> 	Sam
> 
> 
> >  
> >  	/*
> >  	 * If old fb is not mapped to any of the consoles,
> > @@ -939,20 +937,10 @@ static const char *fbcon_startup(void)
> >  	if (fbcon_open(info))
> >  		return NULL;
> >  
> > -	ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> > -	if (!ops) {
> > -		fbcon_release(info);
> > -		return NULL;
> > -	}
> > -
> > -	INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
> > -
> > +	ops = info->fbcon_par;
> >  	ops->currcon = -1;
> >  	ops->graphics = 1;
> >  	ops->cur_rotate = -1;
> > -	ops->cur_blink_jiffies = HZ / 5;
> > -	ops->info = info;
> > -	info->fbcon_par = ops;
> >  
> >  	p->con_rotate = initial_rotation;
> >  	if (p->con_rotate == -1)
> > @@ -1022,7 +1010,7 @@ static void fbcon_init(struct vc_data *vc, int init)
> >  		return;
> >  
> >  	if (!info->fbcon_par)
> > -		con2fb_acquire_newinfo(vc, info, vc->vc_num, -1);
> > +		con2fb_acquire_newinfo(vc, info, vc->vc_num);
> >  
> >  	/* If we are not the first console on this
> >  	   fb, copy the font from that console */
> > -- 
> > 2.33.0

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch