Date: Fri, 12 Oct 2012 17:09:41 -0700 From: Xin Li <delphij@delphij.net> To: Garrett Cooper <yanegomi@gmail.com> Cc: freebsd-current@freebsd.org, d@delphij.net Subject: Re: boot2/loader: serial port handling Message-ID: <5078B145.4090501@delphij.net> In-Reply-To: <CAGH67wQNr%2BZtZPUs-NfLYixEDtzv_O6q4kFhcjFyfacMPfssBw@mail.gmail.com> References: <5078A803.7070705@delphij.net> <CAGH67wQNr%2BZtZPUs-NfLYixEDtzv_O6q4kFhcjFyfacMPfssBw@mail.gmail.com>
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On 10/12/12 17:04, Garrett Cooper wrote:
> On Fri, Oct 12, 2012 at 4:30 PM, Xin Li <delphij@delphij.net>
> wrote:
>> Hi,
>>
>> We have some rather hacky quick hack at $WORK that addresses a
>> problem we have found with boot2/loader and wants to share it and
>> see if we can have more neat solution.
>>
>> Here is the problem: the current boot2 and loader have various
>> places where it considers serial port to exist. When the port is
>> not there, the code would hang because it tests whether the
>> hardware's -READY bit, basically something like:
>>
>> do { } while (inpb(state register) & READY_BIT);
>>
>> This unfortunately would enter an infinite loop when the device
>> is not present -- all in operations would get all bits set.
>>
>> To reproduce this, one can compile boot2/loader with non-existent
>> port and the system will hang at very early stage of boot.
>>
>> ---
>>
>> Because boot2 is size constrained we can not use very
>> sophisticated detection logic there, what I did is to use
>> something like:
>>
>> outb(line control register, word) if (inb(line control register)
>> != word) Disable the serial port read/write
>>
>> For loader I'm not sure if we should use better detection logic.
>> By the way, it seems that the system may force using the default
>> console in loader regardless if the detection logic said no, if
>> it decides that's the only usable one.
>>
>> So what would be the right way to solve these issue?
>
> Have you tried out Andriy's commit yet to loader(8) (r241301)?
Ah I wish I am not this far behind my email backlog. Yes I think
these (241300 and 241301) will solve the problem.
Cheers,
- --
Xin LI <delphij@delphij.net> https://www.delphij.net/
FreeBSD - The Power to Serve! Live free or die
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