Re: [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE

Tetsuo Handa
2020-09-29T01:12:59Z

On 2020/09/29 2:59, Martin Hostettler wrote:
> On Sun, Sep 27, 2020 at 08:46:30PM +0900, Tetsuo Handa wrote:
>> VT_RESIZEX was introduced in Linux 1.3.3, but it is unclear that what
>> comes to the "+ more" part, and I couldn't find a user of VT_RESIZEX.
>>
>
> It seems this is/was used by "svgatextmode" which seems to be at
> http://www.ibiblio.org/pub/Linux/utils/console/
>
> Not sure if that kind of software still has a chance to work nowadays.
>

Thanks for the information.

It seems that v.v_vlin = curr_textmode->VDisplay / (MOFLG_ISSET(curr_textmode, ATTR_DOUBLESCAN) ? 2 : 1)
and v.v_clin = curr_textmode->FontHeight . Thus, v.v_clin is font's height and seems to be non-zero.
But according to https://bugs.gentoo.org/19485 , people are using kernel framebuffer instead.

---------- SVGATextMode-1.10/SVGATextMode.c ----------

/*
* Resize the screen. Still needs LOTS more error checking to avoid dropping out in the middle, leaving
* the user with a garbled screen.
*
* sresize will be TRUE when resizing tty's should be forced (due to the 2nd attempt do_VT_RESIZE will do
* when not enough memory is free).
*
*/

/*
* ALWAYS do a VT_RESIZE, even if we already did a VT_RESIZEX on a 1.3.3 or higher kernel,
* until those kernel programmers make this unambiguous
*/

if (do_VT_RESIZE(curr_textmode->cols, curr_textmode->rows, resize1x1)) sresize=TRUE;

if (check_kernel_version(1,3,3, "VT_RESIZEX"))
{
/*
* VDisplay must de divided by 2 for DoubleScan modes,
* or VT_RESIZEX will fail -- until someone fixes the kernel
* so it understands about doublescan modes.
*/
if (do_VT_RESIZEX(curr_textmode->cols,
curr_textmode->rows,
curr_textmode->VDisplay / (MOFLG_ISSET(curr_textmode, ATTR_DOUBLESCAN) ? 2 : 1),
curr_textmode->FontHeight,
curr_textmode->HDisplay/8*curr_textmode->FontWidth,
curr_textmode->FontWidth, resize1x1)) sresize=TRUE;
}

---------- SVGATextMode-1.10/ttyresize.c ----------

/*
* if VT_RESIZEX not supported (i.e. when compiling on < 1.3.3 kernels), define it.
* this is just te keep the compiler happy
*/

#ifndef VT_RESIZEX
# define VT_RESIZEX 0x560A
typedef struct vt_consize {
ushort v_rows; ushort v_cols; ushort v_vlin; ushort v_clin; ushort v_vcol; ushort v_ccol;
} vt_consize;
#endif

int do_VT_RESIZEX(int cols, int rows, int vlin, int clin, int vcol, int ccol, int allow1x1)
{
struct vt_consize my_vt_size; /* passes the new screen size on to the kernel */
struct vt_consize dummy_vt_size = { 1 , 1 , 1 , 1 , 1 , 1 };
int ram_needed = cols * rows * 2 * MAX_NR_CONSOLES;

my_vt_size.v_rows = rows;
my_vt_size.v_cols = cols;
my_vt_size.v_vlin = vlin;
my_vt_size.v_clin = clin;
my_vt_size.v_vcol = vcol;
my_vt_size.v_ccol = ccol;

PDEBUG(("VT_RESIZEX(cols=%d,rows=%d,vlin=%d,clin=%d,vcol=%d,ccol=%d)\n",cols, rows, vlin, clin, vcol, ccol));

return(generic_VT_RESIZE(&my_vt_size, &dummy_vt_size, allow1x1, ram_needed, VT_RESIZEX, "VT_RESIZEX"));
}