Re: m68k: trying accessing fb memory

Hi Lambert,

thanks, well, i implemented the handler:

static int amcorefb_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
	printk(KERN_INFO "AMCORE frame buffer: mmapping\r\n");

	...
	
}

static struct fb_ops amcorefb_ops = {
	.owner			= THIS_MODULE,
	.fb_open		= amcorefb_open,
	.fb_write		= amcorefb_write,
	.fb_release		= amcorefb_release,
	.fb_pan_display		= amcorefb_pan_display,
	.fb_fillrect		= amcorefb_fillrect,
	.fb_copyarea		= amcorefb_copyarea,
	.fb_imageblit		= amcorefb_imageblit,
 -->    .fb_mmap                = amcorefb_mmap,
};

But "amcorefb_mmap" never get called (no printk output).

mmap(), when used with MAP_SHARED, returns error 19 (ENODEV)

Looking inside nommu.c, seems the error is generated from this line:

	if (flags & MAP_SHARED) {
		/* do checks for writing, appending and locking */
                if ((prot & PROT_WRITE) &&
                   !(file->f_mode & FMODE_WRITE))
                	return -EACCES;

		if (IS_APPEND(file->f_path.dentry->d_inode) &&
                   (file->f_mode & FMODE_WRITE))
                	return -EACCES;

		if (locks_verify_locked(file->f_path.dentry->d_inode))
			return -EAGAIN;

          -->	if (!(capabilities & BDI_CAP_MAP_DIRECT))
          -->		return -ENODEV;


Seems i miss the "get_unmapped_area/BDI_CAP_MAP_DIRECT) capability.
Could this be due to the fact i am using a mainline kernel ?

Regards,
Angelo


On 12/12/2012 22:37, Gavin Lambert wrote:
> Quoth angelo:
>> I have written then a little framebuffer driver for a 128x64 graphic 
>> lcd.
> [...]
>> buffer = mmap( 0, buflen, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 ); 
>> This fails (-1) Then i tried:
>> buffer = mmap( 0, buflen, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0 
>> ); works, returns a valid pointer, but i cannot see any change on the 
>> screen writing in this area.
> 
> Have you read the nommu mmap documentation in the kernel tree?  You have to
> implement an extra handler in your driver in order to support shared mmaps
> on nommu.
> 





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