Re: Gives Bus error in memcpy() in coping /dev/fb0 to a file.

On Thursday 08 March 2007 18:35, Antonino A. Daplas wrote:

On Wed, 2007-03-07 at 17:20 +0530, Vishal Soni wrote:

quoted

[root@tw pcapp]# ./pcapp
1024x768, 16bpp
framebuffer device mapped to memory @ 0xb7db3000.
FB_FRAME mapped to memory @ 0xb7c33000.
Bus error

I don't think vfb's framebuffer can be mmapped.  It's fixable, but
nobody seems to have a need for it,  yet.

Tony

fb is getting successfully mapped.. its just that memcpy gives bus error when
i try to copy the mapped memory of ""framebuffer device"" to a
"""mapped file""""

Well, I am able to get the ball rolling by writing the mapped framebuffer onto
the file by using the below write system call

write(fdout, src, screensize);
/* where fdout = open("./fb_frame", O_RDWR);
and src = (char *)mmap(0, screensize, PROT_READ|PROT_WRITE, MAP_SHARED, fdin,
0); // fdin=open("/dev/fb0", O_RDONLY)
*/

Interesting is that.... why the below code gives problem in memcpy 'ng
with bus error

memcpy(dst, src, screensize);
/*
where src = mmap (0, screensize, PROT_READ, MAP_PRIVATE, fdin, 0));
and
fdin is descriptor of "/dev/fb0"
and
dst = mmap (0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fdout,
0);
and
fdout is descriptor of "./fb_frame" file
*/

Had this fdin not been descriptor of device file "/dev/fb0" but an ordinary
file this method of copying the two files works.

Any clues !!!!!!

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