[U-Boot] [PATCH v2] NS16550: buffer reads

[Wolfgang Denk]

Dear Simon Glass,

In message <CAPnjgZ0RjEhY7-n4=vFACgzpvSgMZJOjaCbngbdB1J2HaxFK6Q at mail.gmail.com> you wrote:
>
> > But that's exactly how it's supposed to work. =A0Depending on hardware
> > that may or may not be FIFOs available to buffer such asynchronous
> > input, and I rather see limited, but consistent behaviour, instead of
> > fancy stuff that works oin one board but not on another.
> 
> Well this is particular serial driver is in pretty widespread use. We

Widespread, yes.  But there is still a huge number of boards where it
is not being used.

> > If you want to run multi-line command sequences, then load and run a
> > script.
> 
> If the setenv commands are configuration commands (such as network
> config, or setting up a new boot path) then they may not already exist
> in the machine. It is much easier to paste commands from a text editor
> / notepad than create a script, put it onto the tftp server, tftp the
> script and run it.

Well, there is two cases:

- You are doing this just once or twice: then it does not make much
  sense to create scripts or use tools; but then it is not too much of
  an issue to copy & paste line by line either.

- You are doing this more frequently.  Then copy & paste is a
  cumbersome and error prone procedure. You have to be careful about
  quoting etc., and errors are not easy to detect.  In such a
  situation it always makes sense to think about more efficient ways:

  1) Use tools.  For example, use something like "expect" or similar
     to send your inout line by line, always waiting for the next
     command prompt.

  2) Use a U-Boot script image which you can download and run.

  3) Use a plain text file which you can "env import".

  4) ...

> > In the special case of setting environment variables, consider using
> > featurs like "env import" instead.
> 
> s/and run it/and "env import" it/

No.  Running a script image is one solution;  using "env import" is
another, independent one.

> > Multi-line input has never been supported.
> 
> Hence this patch, I feel. Pasting a number of lines into the terminal
> is convenient, natural, useful, and when it fails it is unexpected and
> feels like a bug to many. I would certainly like to fix it.

But your patch does not _solve_ the problem.  It just extends the
limits a bit - to som degree that seems to be acceptable to you, but
the next person might paste a few lines more, and it's failing again.

I think it's much better to state clearly that multi-line input is not
supported than to claim it is, without being able to give a precise
limit where it will fail, or without being able to detect error
situations clearly.

Best regards,

Wolfgang Denk

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