[PATCH] notify fbcon if framebuffer registered

Hi,

Note: Please CC: me on replies, since i am not a member of the 
linux-fbdev-devel list!

I am helping a team at handhelds.org to port linux to the ipaq h2210, i 
was trying to get the framebuffer to start when i came across the 
problem, that our fb device is initialized after fb_console_init. I saw 
that sometime between 2.6.1 and 2.6.3 you added a notifier_chain for 
suspend/resume, so i added a new event for newly registered 
framebuffers, this helps my ipaq fb to start, when the kernel starts.

Here is the patch i came up with: (it is a patch based on the 
handhelds.org kernel sources, i hope that it still fits your sources. 
Sorry!)

I basically added a new event in fb.h and notified the event in 
register_framebuffer. I had to move the fb_register_client call in 
fb_console_init up, before "if (!num_registered_fb) because it otherwise 
did not get called in my case. in fbcon_event_notify() i just call 
take_over_console, which is what fb_console_init would have done, had 
the framebuffer been registered before, if i understood it correctly.

Regards, Patty

Index: drivers/video/fbmem.c
===================================================================
RCS file: /cvs/linux/kernel26/drivers/video/fbmem.c,v
retrieving revision 1.13
diff -u -b -r1.13 fbmem.c

--- drivers/video/fbmem.c	29 Feb 2004 01:49:03 -0000	1.13
+++ drivers/video/fbmem.c	1 Mar 2004 13:27:57 -0000

@@ -167,6 +167,7 @@
  extern int tcx_setup(char*);
  extern int leo_init(void);
  extern int leo_setup(char*);
+extern int mq1100fb_init(void);
  extern int kyrofb_init(void);
  extern int kyrofb_setup(char*);

@@ -385,6 +386,9 @@
  #ifdef CONFIG_FB_VOODOO1
  	{ "sstfb", sstfb_init, sstfb_setup },
  #endif
+#ifdef CONFIG_FB_MQ1100
+	{ "mq1100fb", mq1100fb_init, NULL },
+#endif
  #ifdef CONFIG_FB_KYRO
  	{ "kyrofb", kyrofb_init, kyrofb_setup },
  #endif

@@ -1303,6 +1307,9 @@

  	devfs_mk_cdev(MKDEV(FB_MAJOR, i),
  			S_IFCHR | S_IRUGO | S_IWUGO, "fb/%d", i);
+
+    notifier_call_chain (&fb_notifier_list, FB_EVENT_FB_REGISTERED, 

fb_info);
+
  	return 0;
  }

Index: drivers/video/console/fbcon.c
===================================================================
RCS file: /cvs/linux/kernel26/drivers/video/console/fbcon.c,v
retrieving revision 1.3
diff -u -b -r1.3 fbcon.c

--- drivers/video/console/fbcon.c	29 Feb 2004 01:49:04 -0000	1.3
+++ drivers/video/console/fbcon.c	1 Mar 2004 13:27:57 -0000

@@ -2295,6 +2295,10 @@
  	case FB_EVENT_RESUME:
  		fbcon_resumed(info);
  		break;
+    case FB_EVENT_FB_REGISTERED:
+        /* a framebuffer was registered, try to take over the console */
+        take_over_console(&fb_con, first_fb_vc, last_fb_vc, 

fbcon_is_default);
+        break;
  	}
  	return 0;
  }

@@ -2333,16 +2337,15 @@

  int __init fb_console_init(void)
  {
-	if (!num_registered_fb)
-		return -ENODEV;
-	take_over_console(&fb_con, first_fb_vc, last_fb_vc, fbcon_is_default);
  	acquire_console_sem();
  	if (!fbcon_event_notifier_registered) {
  		fb_register_client(&fbcon_event_notifer);
  		fbcon_event_notifier_registered = 1;
  	}
  	release_console_sem();
-
+    if (!num_registered_fb)
+        return -ENODEV;
+    take_over_console(&fb_con, first_fb_vc, last_fb_vc, fbcon_is_default);
  	return 0;
  }

Index: include/linux/fb.h
===================================================================
RCS file: /cvs/linux/kernel26/include/linux/fb.h,v
retrieving revision 1.2
diff -u -b -r1.2 fb.h

--- include/linux/fb.h	29 Feb 2004 01:49:22 -0000	1.2
+++ include/linux/fb.h	1 Mar 2004 13:27:58 -0000

@@ -353,6 +353,8 @@
   *	if you own it
   */
  #define FB_EVENT_RESUME			0x03
+/*	A new framebuffer registered */
+#define FB_EVENT_FB_REGISTERED	0x04

  extern int fb_register_client(struct notifier_block *nb);
  extern int fb_unregister_client(struct notifier_block *nb);


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I am helping a team at handhelds.org to port linux to the ipaq h2210, i 
was trying to get the framebuffer to start when i came across the 
problem, that our fb device is initialized after fb_console_init. 

Is your driver built as a module? That is the only way that could happen 
that I know of. The new behavior is that the fbdev device doesn't not 
automatically take over the console. You use the app con2fb to do that.
The reason was so developers could debug there drivers easily. Alot of 
times there is a bug in the xxfb_init code and you end up with a blank 
display. Very hard to work with. Also some fbdev drivers can work with 
vgacon. So you could run a fbdev app on vgacon!!! In this case you don't 
want the fbdev device changing the hardware. 
   Actually you don't really need fbcon for embedded devices except for 
debugging output. If your device is embedded and without fbcon you can 
call fb_set_var before you register the device.

I saw 
that sometime between 2.6.1 and 2.6.3 you added a notifier_chain for 
suspend/resume, so i added a new event for newly registered 
framebuffers, this helps my ipaq fb to start, when the kernel starts.

Here is the patch i came up with: (it is a patch based on the 
handhelds.org kernel sources, i hope that it still fits your sources. 
Sorry!)

I basically added a new event in fb.h and notified the event in 
register_framebuffer. I had to move the fb_register_client call in 
fb_console_init up, before "if (!num_registered_fb) because it otherwise 
did not get called in my case. in fbcon_event_notify() i just call 
take_over_console, which is what fb_console_init would have done, had 
the framebuffer been registered before, if i understood it correctly.

This patch could come in handy for hotplug events :-) We would also need a 
unregister event. The only thing is you have to do some filtering here.
Say you have a multi-head system. If question you have is do you want to 
register this device to the fbcon system. The second question is to which 
VCs do you map this device. In fbcon you have a map for that. I have to 
think about how to do that. Your patch is a great start. I just need to 
go over the different possible cases we can have.
 

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Hi,

thanks for your reply!

Is your driver built as a module? That is the only way that could happen 
that I know of. The new behavior is that the fbdev device doesn't not 
automatically take over the console. You use the app con2fb to do that.
The reason was so developers could debug there drivers easily. Alot of 
times there is a bug in the xxfb_init code and you end up with a blank 
display. Very hard to work with. Also some fbdev drivers can work with 
vgacon. So you could run a fbdev app on vgacon!!! In this case you don't 
want the fbdev device changing the hardware. 
  Actually you don't really need fbcon for embedded devices except for 
debugging output. If your device is embedded and without fbcon you can 
call fb_set_var before you register the device.

 

The driver is not compiled as a module, but still fb_console_init runs 
before mq11xxfb_init, originally i just called fb_console_init from 
within my probe function which worked but was a very ugly way to go, so 
i came up with the framebuffer_register notification, and since i saw 
that you added event_notifications in kernel 2.6.3, i adapted my 
notification and thought i could send you the patch.
It works perfectly for me, sicne my main problem is, that i dont have a 
serial cable and can only login to my device thru infrared serial port 
which only starts when linuxrc of initrd is running, thus i needed a way 
to see kernel messages and the fb seemed an easy way to do that. Thats 
what i needed the patch for, and it works perfectly for me, i dont need 
to call any applications, just as soon as my (statically compiled) fb is 
registered, the fbcon comes up and shows me the boot messages.
I agree that it is only needed for debugging output, thats all i 
currently need it for.

quoted

This patch could come in handy for hotplug events :-) We would also need a 
unregister event. The only thing is you have to do some filtering here.
Say you have a multi-head system. If question you have is do you want to 
register this device to the fbcon system. The second question is to which 
VCs do you map this device. In fbcon you have a map for that. I have to 
think about how to do that. Your patch is a great start. I just need to 
go over the different possible cases we can have.

   

I'm very glad if you can use the patch, actually i am not very deep into 
the internals of the fbcon, i just saw, that by calling 
take_over_console, i can reach my goal, i did not think about any 
complications or problems, since i dont know enough about the fbcon.

Regards, Patty


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