[U-Boot] What's purpose of DEV_FLAGS_SYSTEM and DEV_EXT_VIDEO?

[Bin Meng]

Hi,

I plan to send a patch to remove the DEV_FLAGS_SYSTEM and
DEV_EXT_VIDEO. They look useless to me. For example,

$ grep -nr DEV_FLAGS_SYSTEM *
arch/blackfin/cpu/jtag-console.c:186:   dev.flags = DEV_FLAGS_OUTPUT |
DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
board/bf527-ezkit/video.c:442:  videodev.flags = DEV_FLAGS_SYSTEM;
 /* No Output */
board/kosagi/novena/novena.c:80:                .flags  =
DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM,
board/cm-bf548/video.c:336:     videodev.flags = DEV_FLAGS_SYSTEM;
 /* No Output */
board/mpl/common/kbd.c:206:     kbddev.flags =  DEV_FLAGS_INPUT |
DEV_FLAGS_SYSTEM;
board/mpl/pati/pati.c:569:      pci_con_dev.flags = DEV_FLAGS_OUTPUT |
DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
board/bf548-ezkit/video.c:332:  videodev.flags = DEV_FLAGS_SYSTEM;
 /* No Output */
board/bf533-stamp/video.c:168:  videodev.flags = DEV_FLAGS_SYSTEM;
common/cmd_console.c:33:                        (dev->flags &
DEV_FLAGS_SYSTEM) ? 'S' : '.',
common/usb_kbd.c:505:   usb_kbd_dev.flags =  DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
common/stdio.c:91:      dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT
| DEV_FLAGS_SYSTEM;
common/stdio.c:102:     dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT
| DEV_FLAGS_SYSTEM;
drivers/input/cros_ec_keyb.c:261:       dev.flags = DEV_FLAGS_INPUT |
DEV_FLAGS_SYSTEM;
drivers/input/tegra-kbc.c:361:  dev.flags = DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
drivers/input/keyboard.c:277:   kbddev.flags =  DEV_FLAGS_INPUT |
DEV_FLAGS_SYSTEM;
drivers/video/cfb_console.c:2296:       console_dev.flags =
DEV_FLAGS_OUTPUT | DEV_FLAGS_SYSTEM;
drivers/net/netconsole.c:325:   dev.flags = DEV_FLAGS_OUTPUT |
DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
include/stdio_dev.h:19:#define DEV_FLAGS_SYSTEM 0x80000000      /*
Device is a system device            */

Except for this one below which tests the flag and prints an 'S',
common/cmd_console.c:33:                        (dev->flags &
DEV_FLAGS_SYSTEM) ? 'S' : '.',

I don't see any actual meaning of this flag. I wonder if someone on
the mailing list knows the history.

Also I noticed that several blackfin boards' video driver only set
this flag without setting DEV_FLAGS_OUTPUT.

board/bf527-ezkit/video.c:442:  videodev.flags = DEV_FLAGS_SYSTEM;
 /* No Output */
board/cm-bf548/video.c:336:     videodev.flags = DEV_FLAGS_SYSTEM;
 /* No Output */
board/bf548-ezkit/video.c:332:  videodev.flags = DEV_FLAGS_SYSTEM;
 /* No Output */
board/bf533-stamp/video.c:168:  videodev.flags = DEV_FLAGS_SYSTEM;

I wonder these video drivers are not used for system output purpose?

Regards,
Bin