Re: kexec and framebuffer

["Antonino A. Daplas" <adaplas@gmail.com>]

Kalev Lember wrote:
> Gerd Hoffmann wrote:
>>> I am wondering what would be the preferred method to extract screen_info
>>> from running kernel. Should this be made available from sysfs or maybe a
>>> new system call be created?
>>>     
>> Simply ask /dev/fb0?
>> Patch for kexec tools attached.
>>   
> Thank you, this was really helpful.
>> +	if (0 != strcmp(fix.id, "vesafb"))
>> +		goto out;
> I think this check should be removed so that other framebuffer drivers
> besides vesafb would also work.

I think having the check is correct, only vesafb relies totally on
screen_info. If you remove the check, you can get the wrong information
from other framebuffer drivers.

> +	/* fixme: better get size from /proc/iomem */
> +	real_mode->lfb_size       = (fix.smem_len + 65535) / 65536;
> +	real_mode->pages          = (fix.smem_len + 4095) / 4096;

Note that fix.smem_len is the size of the remapped memory which can be
smaller than the actual framebuffer length. But there's a fixme comment
there so you probably know about this.
 
> Additionally the fix.id is "VESA VGA",
> not "vesafb".

Yes.

Tony