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Message-ID: <YgJ19zts7nxCjGk5@phenom.ffwll.local>
Date: Tue, 8 Feb 2022 14:53:59 +0100
From: Daniel Vetter <daniel@...ll.ch>
To: Sam Ravnborg <sam@...nborg.org>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>,
DRI Development <dri-devel@...ts.freedesktop.org>,
linux-fbdev@...r.kernel.org,
Thomas Zimmermann <tzimmermann@...e.de>,
Du Cheng <ducheng2@...il.com>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
LKML <linux-kernel@...r.kernel.org>,
Claudio Suarez <cssk@...-c.es>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 13/21] fbcon: move more common code into fb_open()
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@...el.com>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> > Cc: Thomas Zimmermann <tzimmermann@...e.de>
> > Cc: Claudio Suarez <cssk@...-c.es>
> > Cc: Du Cheng <ducheng2@...il.com>
> > ---
> > 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
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