From: "Antonino A. Daplas" On a vc resize, the contents of the old screen buffer are transferred to the new screenbuffer. If the new screenbuffer is smaller than the old one, only the contents from the bottom are copied to new. If the contents of the old buffer are located at the top, then the contents will not be copied to the new buffer resulting in a blank screen. This bug will happen only if the vc in question is not in the foreground. Doing an fbset -a or con2fbmap will trigger this bug. To fix this problem, base the start of the copy from the location of the current cursor. If the cursor is near the top of the buffer, copy the contents at the top, and if the cursor is near the bottom of the buffer, then copy the contents at the bottom. In the unlikely case where the new row size is greater than 2x smaller than the old one, and the cursor is in the middle, copy 1/2 screenful from the top and bottom of the cursor position. Signed-off-by: Antonino Daplas Signed-off-by: Andrew Morton --- drivers/char/vt.c | 37 +++++++++++++++++++++++++++++++------ 1 files changed, 31 insertions(+), 6 deletions(-) diff -puN drivers/char/vt.c~console-fix-buffer-copy-on-vc-resize drivers/char/vt.c --- devel/drivers/char/vt.c~console-fix-buffer-copy-on-vc-resize 2005-08-21 21:54:01.000000000 -0700 +++ devel-akpm/drivers/char/vt.c 2005-08-21 21:54:01.000000000 -0700 @@ -751,6 +751,7 @@ int vc_resize(struct vc_data *vc, unsign unsigned long old_origin, new_origin, new_scr_end, rlth, rrem, err = 0; unsigned int old_cols, old_rows, old_row_size, old_screen_size; unsigned int new_cols, new_rows, new_row_size, new_screen_size; + unsigned int end; unsigned short *newscreen; WARN_CONSOLE_UNLOCKED(); @@ -794,20 +795,44 @@ int vc_resize(struct vc_data *vc, unsign old_origin = vc->vc_origin; new_origin = (long) newscreen; new_scr_end = new_origin + new_screen_size; - if (new_rows < old_rows) - old_origin += (old_rows - new_rows) * old_row_size; + + if (vc->vc_y > new_rows) { + if (old_rows - vc->vc_y < new_rows) { + /* + * Cursor near the bottom, copy contents from the + * bottom of buffer + */ + old_origin += (old_rows - new_rows) * old_row_size; + end = vc->vc_scr_end; + } else { + /* + * Cursor is in no man's land, copy 1/2 screenful + * from the top and bottom of cursor position + */ + old_origin += (vc->vc_y - new_rows/2) * old_row_size; + end = old_origin + new_screen_size; + } + } else + /* + * Cursor near the top, copy contents from the top of buffer + */ + end = (old_rows > new_rows) ? old_origin + new_screen_size : + vc->vc_scr_end; update_attr(vc); - while (old_origin < vc->vc_scr_end) { - scr_memcpyw((unsigned short *) new_origin, (unsigned short *) old_origin, rlth); + while (old_origin < end) { + scr_memcpyw((unsigned short *) new_origin, + (unsigned short *) old_origin, rlth); if (rrem) - scr_memsetw((void *)(new_origin + rlth), vc->vc_video_erase_char, rrem); + scr_memsetw((void *)(new_origin + rlth), + vc->vc_video_erase_char, rrem); old_origin += old_row_size; new_origin += new_row_size; } if (new_scr_end > new_origin) - scr_memsetw((void *)new_origin, vc->vc_video_erase_char, new_scr_end - new_origin); + scr_memsetw((void *)new_origin, vc->vc_video_erase_char, + new_scr_end - new_origin); if (vc->vc_kmalloced) kfree(vc->vc_screenbuf); vc->vc_screenbuf = newscreen; _