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

[Bin Meng]

Hi,

On Thu, Sep 3, 2015 at 6:25 AM, Anatolij Gustschin <agust at denx.de> wrote:
> Hi Bin,
>
> On Mon, 17 Aug 2015 13:09:20 +0800
> Bin Meng <bmeng.cn at gmail.com> wrote:
> ...
>> 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 *
> ...
>> 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.
>
> This is very old code, and I do not know the history. Both flags could
> be dropped, I've no objection.
>
>> 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?
>
> No, they don't. In the board configs I see that these use very small
> Displays (320x240). These shows the logo, but it would be very difficult
> to use such displays as a console.
>

Thanks all for the information. I will see if I can spend some time to
clean these up.

Regards,
Bin