explicit refresh?

explicit refresh?

[Laszlo Ersek]

Hi,

this is a dumb question and it's not appropriate for a development
mailing list, but I couldn't find "grub-user" or "grub-users", so I'll
ask here anyway...

My laptop is connected to my workstation via USB-serial (USB for the
laptop, serial for the workstation). Sometimes, by the time the laptop
comes up and starts "screen", for viewing the serial output from the
workstation, the workstation is already displaying the grub menu.
Occasionally in this case, I can't see anything at all, there's no grub
countdown, the cursor up/down keys do nothing (they certainly don't
refresh the screen), but if I blindly press Enter, then the selected
kernel entry is booted okay (and that kernel does produce serial output,
and takes the LUKS password from serial fine as well).

So, Q1: what could cause the loss of serial output from grub when I
connect to it "too late"?

Q2: when that happens, can I press something like C-r to force a full
serial / screen refresh?

I know that USB-serial adaptors are generally wacky, but this is a
Prolific PL2303 adaptor which is (to my knowlede) usually considered
reliable. Plus, my laptop has no physical RS/232 port (shame on you, all
laptop vendors of today!), so this is the best I can do.

Thanks,
Laszlo

Re: explicit refresh?

[Lennart Sorensen]

On Wed, Feb 08, 2017 at 09:29:36AM +0100, Laszlo Ersek wrote:
> Hi,
> 
> this is a dumb question and it's not appropriate for a development
> mailing list, but I couldn't find "grub-user" or "grub-users", so I'll
> ask here anyway...
> 
> My laptop is connected to my workstation via USB-serial (USB for the
> laptop, serial for the workstation). Sometimes, by the time the laptop
> comes up and starts "screen", for viewing the serial output from the
> workstation, the workstation is already displaying the grub menu.
> Occasionally in this case, I can't see anything at all, there's no grub
> countdown, the cursor up/down keys do nothing (they certainly don't
> refresh the screen), but if I blindly press Enter, then the selected
> kernel entry is booted okay (and that kernel does produce serial output,
> and takes the LUKS password from serial fine as well).
> 
> So, Q1: what could cause the loss of serial output from grub when I
> connect to it "too late"?
> 
> Q2: when that happens, can I press something like C-r to force a full
> serial / screen refresh?
> 
> I know that USB-serial adaptors are generally wacky, but this is a
> Prolific PL2303 adaptor which is (to my knowlede) usually considered
> reliable. Plus, my laptop has no physical RS/232 port (shame on you, all
> laptop vendors of today!), so this is the best I can do.

Actually I would say PL2303 are usually considered quite unreliable.
Doesn't help that there are lots of fakes on the market that are even
worse.

-- 
Len Sorensen

Re: explicit refresh?

[Andrei Borzenkov]

08.02.2017 11:29, Laszlo Ersek пишет:
> Hi,
> 
> this is a dumb question and it's not appropriate for a development
> mailing list, but I couldn't find "grub-user" or "grub-users", so I'll
> ask here anyway...
> 

there is help-grub@gnu.org

> My laptop is connected to my workstation via USB-serial (USB for the
> laptop, serial for the workstation). Sometimes, by the time the laptop
> comes up and starts "screen", for viewing the serial output from the
> workstation, the workstation is already displaying the grub menu.
> Occasionally in this case, I can't see anything at all, there's no grub
> countdown, the cursor up/down keys do nothing (they certainly don't
> refresh the screen), but if I blindly press Enter, then the selected
> kernel entry is booted okay (and that kernel does produce serial output,
> and takes the LUKS password from serial fine as well).
> 
> So, Q1: what could cause the loss of serial output from grub when I
> connect to it "too late"?
> 
> Q2: when that happens, can I press something like C-r to force a full
> serial / screen refresh?
> 

There are no hot keys for "refresh everything". May be adding it would
be not so bad idea.

> I know that USB-serial adaptors are generally wacky, but this is a
> Prolific PL2303 adaptor which is (to my knowlede) usually considered
> reliable. Plus, my laptop has no physical RS/232 port (shame on you, all
> laptop vendors of today!), so this is the best I can do.
> 
> Thanks,
> Laszlo
> 
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