Laszlo,
As far as adding a PCD or not, there is another option.
The UEFI Specification defines 4 GUIDs for terminal types that are used in
VenMedia() device path nodes and provides the information a terminal driver
needs to know to translate a bytes stream to/from a specific type of terminal
into UEFI protocol interfaces.
The terminal GUIDs are defined in EDK II in MdePkg/Include/Guid/PcAnsi.h
#define EFI_PC_ANSI_GUID \
{ \
0xe0c14753, 0xf9be, 0x11d2, {0x9a, 0x0c, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d
} \
}
#define EFI_VT_100_GUID \
{ \
0xdfa66065, 0xb419, 0x11d3, {0x9a, 0x2d, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d
} \
}
#define EFI_VT_100_PLUS_GUID \
{ \
0x7baec70b, 0x57e0, 0x4c76, {0x8e, 0x87, 0x2f, 0x9e, 0x28, 0x08, 0x83, 0x43
} \
}
#define EFI_VT_UTF8_GUID \
{ \
0xad15a0d6, 0x8bec, 0x4acf, {0xa0, 0x73, 0xd0, 0x1d, 0xe7, 0x7e, 0x2d, 0x88
} \
}
extern EFI_GUID gEfiPcAnsiGuid;
extern EFI_GUID gEfiVT100Guid;
extern EFI_GUID gEfiVT100PlusGuid;
extern EFI_GUID gEfiVTUTF8Guid;
If we want to support terminal emulators that do not exactly match one of these
4 terminal types, then additional terminal types can be added to the EDK II
implementation.
I recommend that terminal types that are not defined by UEFI Specification be
added to MdeModulePkg and the TerminalDxe driver can add support for these
additional terminal types. The only reason to add a feature flag PCD with this
direction is if there is a concern on the size impact of building in support
for the additional terminal types in TerminalDxe.
Best regards,
Mike
-----Original Message-----
From: Laszlo Ersek [mailto:[email protected]]
Sent: Friday, May 08, 2015 2:51 AM
To: Roy Franz
Cc: [email protected]; [email protected]
Subject: Re: [edk2] [PATCH] Treat ASCII DEL (0x7f) as backspace
On 05/08/15 04:26, Roy Franz wrote:
> On Thu, May 7, 2015 at 7:03 PM, Kinney, Michael D
> <[email protected]> wrote:
>> Roy,
>>
>> Did you try the command line at the UEFI Shell prompt through a
>> serial terminal? There is line editing available, where backspace
>> and delete keys perform different actions. I think your change
>> prevents a user from ever getting the delete key behavior. Same
>> would be true for the UEFI Shell command EDIT that provides a text
>> file editor.
>
> Hi Mike,
>
> I did do my testing at the UEFI shell prompt with line editing.
> While my patch does remove the use of the ASCII DEL character, there
> are 3 other terminal escape sequences that are also used for delete.
> In terraterm over serial, the delete key still works as expected, so
> it is using an escape sequence. For hyperterm, delete doesn't work
> before or after my change. For the Linux terminal cases, delete
> doesn't work at all, as they all use a 3 character VT220 escape "[3~"
> for delete which EDK2 does not accept. So this certainly will
> negatively affect terminals that send ASCII DEL (0x7f), but I was not
> able to find one that did.
I think this email provides good background:
https://lists.debian.org/debian-i18n/1998/04/msg00015.html
> If this change isn't globally acceptable, I'm fine with restricting
> this to a terminal type, or making this otherwise configurable (maybe
> with a fixed PCD?)
Please make this configurable with a fixed PCD or feature PCD.
The key in the upper right corner on my PC keyboard, labeled
<- Backspace
emits keysim BackSpace, and XLookupString gives 0x08, according to "xev".
The key labeled
Delete
emits keysim Delete, and XLookupString gives 0x7F, according to "xev".
Both keys work as expected in all the applications I use, both on the
character console and under X (ie. the former key removes the previous
character, the latter key removes the next character).
This holds for the UEFI shell as well, when it runs as part of OVMF or
ArmVirtualizationQemu, and is accessed over the QEMU serial console,
from xterm.
> This fixes a longstanding annoyance (ie backspace
> key not working) on Linux platforms, which I would like to get fixed,
> whether via this patch or a similar one.
Most Linux distributions' default settings are horribly broken in this area.
<rant>
The fact that most applications *agree* on those broken settings doesn't
make them less broken.
The obsession on Linux with VT100/VT220 is ridiculous. I was born in the
seventies and have never seen a VT100/VT220 keyboard. It's 2015 and we
use PC keyboards. Hence, since 1998, I've been doing my part to bludgeon
all my applications and remote Linux accounts to do the right thing.
Backspace is ^H, Delete is ^?; I own a PC, not some kind of electronic
relic.
</rant>
So, please make this change dependent on a feature PCD, and the default
behavior shouldn't change.
Thanks!
Laszlo
>
> As an aside, while reviewing the DEL escape codes, I see a simpler way
> to do this patch, so the current version should not be used.
>
> Thanks,
> Roy
>
>
>>
>> Thanks,
>>
>> Mike
>>
>> -----Original Message-----
>> From: Roy Franz [mailto:[email protected]]
>> Sent: Thursday, May 07, 2015 4:33 PM
>> To: [email protected]; [email protected]; Tian,
>> Feng
>> Subject: [edk2] [PATCH] Treat ASCII DEL (0x7f) as backspace
>>
>> Most Linux terminal emulators use ASCII 0x7f (^?) for backspace,
>> rather than 0x08 (^H) since ^H is used by some programs for other
>> purposes, such as help menus. This results in backspace not working
>> in most Linux environments, particularly in emulated environments
>> such as QEMU where telnet or xterm may be used to connect to
>> the emulated UART. While in some cases this can be configured in the
>> terminal emulator, it must be done on every connection, as if
>> permently configured this will break all other uses of the terminal.
>>
>> This change causes both ASCII 0x08 and 0x7F to be treated as
>> backspace. This provides a working backspace when tested with
>> minicom, screen, telnet, and xterm under Linux. I also tested
>> teraterm and hyperterm under Windows connecting via rs232, and
>> saw no regressions. (The delete key doesn't work on hyperterm
>> both before and after the change)
>>
>> This change removes the ASCII encoding for delete, however
>> this did not cause regressions on any tested terminal emulators
>> as they do not use the ASCII encoding for the delete key.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.0
>> Signed-off-by: Roy Franz <[email protected]>
>> ---
>> MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
>> b/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
>> index 4a008c9..c92d3d4 100644
>> --- a/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
>> +++ b/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
>> @@ -1212,6 +1212,14 @@ UnicodeToEfiKey (
>> switch (TerminalDevice->InputState) {
>> case INPUT_STATE_DEFAULT:
>>
>> + switch (UnicodeChar) {
>> + case 0x7f:
>> + UnicodeChar = CHAR_BACKSPACE;
>> + break;
>> + default :
>> + break;
>> + }
>> +
>> break;
>>
>> case INPUT_STATE_ESC:
>> --
>> 1.9.1
>>
>>
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