Re: m68k: trying accessing fb memory

I confirm there is no chance to use framebuffer mmap() and MAP_SHARED to
access framebuffer screen memory with _coldfire_ _mcf5307_.

Actually, i call

buffer = mmap(0, buflen, PROT_WRITE, MAP_SHARED, fd, 0);

over fd open on "/dev/fb0" as ORDWR.

Call fail inside
mm/nommu.c, validate_mmap_request(), line 920



              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))
                        {
-->                             printk (KERN_INFO "ENODEV 2\n");
 -->                            return -ENODEV;
                        }


So, as i explained, i cannot have BDI_CAP_MAP_DIRECT for this
architecture, and the mmap call using MAP_SHARED fails.

Looking the code, error is still at a mmap params "validation" level,
and far from any "fb_mmap" to get called.

Code is complex, and still i can miss something. Anyway i hope you can
confirm i cannot use mmap() to access framebuffer for this cpu, or
maybe, you can suggest me some example that can do it.

Regards,
Angelo


On 12/12/2012 23:21, Gavin Lambert wrote:
> Quoth angelo:
>> thanks, well, i implemented the handler:
>>
>> static int amcorefb_mmap(struct fb_info *info, struct vm_area_struct
>> *vma) {
> 
> No, that's not the right one.  You don't need to implement that.
> 
>> Seems i miss the "get_unmapped_area/BDI_CAP_MAP_DIRECT) capability.
> 
> fbmem.c implements the main get_unmapped_area handler.  In your framebuffer
> driver you just need to either implement fb_get_unmapped_area or (easier,
> but only works on nommu) set fix.smem_start and .smem_len correctly in your
> fb_info.
> 

-- 


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