Re: [PATCH 1/4] ARM STM/i.MX: Allocate memory for framebuffer during probe

[Juergen Beisert <jbe@pengutronix.de>]

Gregory CLEMENT wrote:
> On 01/04/2011 03:46 PM, Juergen Beisert wrote:
> > Gregory CLEMENT wrote:
> >> With current code when the framebuffer is register, screen_base is not
> >> set yet. So when we want to access framebuffer from mmap we get a
> >> pointer to 0x0 instead of getting the pointer to the framebuffer
> >> address. This patch fix this bug by allocating memory for framebuffer
> >> during probe just before registering framebuffer driver.
> >
> > Are you sure? See below
>
> It was the value I get at runtime at least.
>
> >> Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
>
> [...]
>
> > This probe function sets up the default mode. And register_framebuffer()
> > itself calls stmfb_activate_var() which calls stmfb_memory_mmgt(). So,
> > when the call to register_framebuffer() returns the 'screen_base' should
> > no longer be NULL.
>
> But in register_framebuffer first map_base get its value from screen_base
> and it is only after that fb_activate_var is called. And the problem is
> that mmap will not get screen_base but map_base and this one is set too
> early. Extract from  register_framebuffer() in fb.c:
>
> 	info->cdev.dev->map_base = (unsigned long)info->screen_base;
> map_base get its value here ------^
> 	info->cdev.dev->size = info->cdev.size;
>
> 	dev = &info->dev;
> 	dev->priv = info;
> 	dev->id = id;
>
> 	sprintf(dev->name, "fb");
>
> 	register_device(&info->dev);
> 	dev_add_param(dev, "enable", fb_enable_set, NULL, 0);
> 	dev_set_param(dev, "enable", "0");
>
> 	if (info->num_modes && (info->mode_list != NULL) &&
> 			(info->fbops->fb_activate_var != NULL)) {
> 		dev_add_param(dev, "mode_name", fb_setup_mode, NULL, 0);
> 		dev_set_param(dev, "mode_name", info->mode_list[0].name);
> fb_activate_var is called here ------------------------^

And this call will call driver's stmfb_activate_var() (and(!) 
stmfb_memory_mmgt()).
But I will check it again.

jbe

-- 
Pengutronix e.K.                              | Juergen Beisert             |
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