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

On Thu, Feb 10, 2022 at 12:46:32PM +0100, Thomas Zimmermann wrote:

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.

Yeah further patches clean this up more. Or did you see a potential bug here? I did ditch the fb_release error handling, simply because there's not really much we can do anyway, it shouldn't ever fail (that's a driver bug) and it was convoluting the code for no gain. But I might have missed something in this cargo-cult. -Daniel

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