/dev/fb0: No such device but i can see it

marius_c · 02-11-2010, 05:53 PM

Kernel: 2.6.28-15-generic
Ubuntu 9.X #52-Ubuntu SMP

Driver. Video, build on top of skeleton video driver.
I can insert it and remove it using:

insmod / rmmod
or with modprobe
modprobe working if i move the *.ko file in
/lib/modules/`uname -r`/kernel/drivers/misc/
and I depmod after. I can inser and remove it.

-lsmod lists the module 'myfb'.
-ls /proc/devices shows it as '29 fb'
-ls /dev/fb* lists fb0, so the file is there.

But when i try to

sudo cat /dev/fb0 > myfile
I got
cat: /dev/fb0: No such device

Thx.

Simon Bridge · 02-12-2010, 02:08 AM

You are making a custom framebuffer driver?

Quote:

ls /dev/fb* lists fb0, so the file is there.

Yes, but you actually have to issue the command and copy/paste it and the result here so we can see what you do. That way your report looks like this:

Code:

$ lsmod | grep fb
fbcon                  36640  72 
tileblit                2460  1 fbcon
font                    8124  1 fbcon
bitblit                 5372  1 fbcon

$ ls /proc/devices
/proc/devices

$ ls -l /dev/fb*
crw-rw---- 1 root video 29, 0 2010-02-08 01:20 /dev/fb0

$ cat /dev/fb0 > myfile
$

(In my case it worked).

See how I have put the command as well as the result? This way it is unambiguous what I have done and others can be confident they have all the facts. (Note the -l option in the ls command? That is important because your error says "no such device" not "no such file" - perhaps it is the wrong kind of file?)

marius_c · 02-12-2010, 03:33 PM

Hi here are all the commands copied from console.

no fb, inserting...

Code:

home$ ls /dev/f*
/dev/fd0  /dev/full  /dev/fuse

/dev/fd:
0  1  2  3

(u32)marius@A64-2:~$ lsmod | more
Module                  Size  Used by
binfmt_misc            16776  1 
bridge                 56212  0 
stp                    10500  1 bridge
--More--

ls
avs_1.o      
Makefile
modules.order
avs_1.ko
avs_1.c

home$ sudo insmod ./avs_1.ko
home$ dmesg
[  321.920334] d_screen_init 
[  321.920339] sf_create(struct platform_device *pdev)
[  321.920548] local_register_framebuffer(struct fb_info* pfionfo) 
[  321.920884] Console: switching to colour frame buffer device 80x30
home$

inserted. so look for it

Code:

home$ ls /dev/f*
/dev/fb0  /dev/fd0  /dev/full  /dev/fuse

/dev/fd:
0  1  2  3
home$ 

home$ ls -l /dev/fb*
crw-rw---- 1 root video 29, 0 2010-02-12 16:17 /dev/fb0
home$ 


home$ lsmod | grep fb
fbcon                  46112  72 
tileblit               10752  1 fbcon
font                   16384  1 fbcon
bitblit                13824  1 fbcon
home$ 

home$ sudo cat /proc/devices | grep f
[sudo] password for marius: 
 29 fb
216 rfcomm
  2 fd
home$

but... Is somehting wrong with my driver ?

Code:

home$ sudo cat /dev/fb0 >~/dataa
cat: /dev/fb0: No such device
home$

Simon Bridge · 02-17-2010, 02:53 AM

Is there already a framebuffer driver in place instead of yours?

marius_c · 02-17-2010, 03:29 PM

No, at the top of my outputs it ca be seen before inserting my driver.

Code:

home$ ls /dev/f*
/dev/fd0  /dev/full  /dev/fuse

/dev/fd:
0  1  2  3

(u32)marius@A64-2:~$ lsmod | more
Module                  Size  Used by
binfmt_misc            16776  1 
bridge                 56212  0 
stp                    10500  1 bridge

Simon Bridge · 02-17-2010, 11:58 PM

http://lists.mplayerhq.hu/pipermail/...er/037840.html

You get ENOENT (No such file or directory) if the device node doesn't exist in the filesystem. If you see ENODEV (No such device), then the device node has major/minor number which the
kernel does not recognize as a valid device, i.e. you haven't compiled in the driver or loaded the module.

Possibly your driver is not compatible with your video card.
So you see the file there, but there is no physical device associated with it.