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Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on

From Dimiter_Popoff <dp@tgi-sci.com>
Newsgroups comp.arch.embedded
Subject Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on
Date 2021-10-25 00:50 +0300
Organization TGI
Message-ID <sl4kf7$e4r$1@dont-email.me> (permalink)
References (1 earlier) <sl3d4h$17d3$1@gioia.aioe.org> <sl3f65$jdl$1@dont-email.me> <sl4dm3$5ut$1@dont-email.me> <sl4fk0$2si$1@dont-email.me> <sl4i03$784$1@dont-email.me>

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On 10/25/2021 0:08, Don Y wrote:
> On 10/24/2021 1:27 PM, Dimiter_Popoff wrote:
> ....
>>
>> Whatever handshakes he makes there is no problem knowing whether
>> the fifo is full - just check if the position the write pointer
>> will have after putting the next byte matches the read pointer
>> at the moment.  Like I said before, few things are simpler than
>> that, can't imagine someone working as a programmer being
>> stuck at *that*.
> 
> Yes, but if you want to implement flow control, you have to tell the
> other end of the line BEFORE you've filled your buffer.  There may be
> a character being deserialized AS you are retrieving the "last"
> character, another one (or more) preloaded into the transmitter on
> the far device, etc.  And, it will take some time for your
> notification to reach the far end and be recognized as a desire
> to suspend transmission.  etc.
> 
> If you wait until you have no more space available, you are almost
> certain to lose characters.

Well of course so, we have all done that sort of thing since the 80-s,
other people have done it before I suppose. Implementing fifo thresholds
is not (and has never been) rocket science.
The point is there is no point in throwing huge efforts at a
self-inflicted problem instead of just doing it the easy way which
is well, common knowledge.

> 
>>>> Although this thread is on how to wrestle a poor
>>>> language to do what you want, sort of how to use a hammer on a screw
>>>> instead of taking the screwdriver, there would be no need to
>>>> mask interrupts with C either.
>>>
>>> The "problem" with the language is that it gives the compiler the 
>>> freedom
>>> to make EQUIVALENT changes to your code that you might not have foreseen
>>> or that might not have been consistent with your "style" -- yet do not
>>> alter the results.
>>
>> Don, let us not go into this. Just looking at the thread is enough to
>> see it is about wrestling the language so it can be made some use of.
> 
> The language isn't the problem.  Witness the *millions* (?) of programs
> written in it, over the past 5 decades.

This does not prove much, it has been the only language allowing
"everybody" to do what they did. I am not denying this is the best
language currently available to almost everybody. I just happened to
have been daring enough to explore my own way/language and have seen
how much is there to be gained if not having to wrestle a language
which is just a more complete phrase book than the rest of the
phrase books (aka high level languages).


>> Indeed you don't want to write how the equation is solved every time.
>> This is why you can call it once you have it available. This is language
>> independent.
> 
> For a simple quadratic, you can explore the coefficients to determine which
> algorithm is best suited to giving you *accurate* results. >
> What if I present *any* expression?  Can you have your solution available
> to handle any case?  Did you even bother to develop such a solution if you
> were only encountering quadratics?

Any expression solver has its limitations, why go into that? Mine (in
the dps environment) can do all arithmetic and logic for
integers, the fp can do all arithmetic, knows pi, e, haven't needed
to expand it for years. And again, solving expressions has never taken
me any significant part of the effort on a project.


> I've made some syntactic changes to my code that make it much easier
> to read -- yet mean that I have to EXPLAIN how they work and why they
> are present as any other developer would frown on encountering them.

Oh I am well aware of the value of standardization and popularity,
these are the strongest points of C.

> (But, it's my opinion that, once explained, that developer will see them
> as an efficient addition to the language in line with other *existing*
> mechanisms that are already present, there).

Of course, but you have to have them on board first...

>> Similar to say Chinese, very popular, spoken by billions, yet
>> where are its literary masterpieces. Being hieroglyph based there
>> are none; you will have to look at alphabet based languages to
>> find some.
> 
> One can say the same thing about Unangax̂ -- spoken by ~100!
> Popularity and literary masterpieces are completely different
> axis.
> 
> Hear much latin or ancient greek spoken, recently?

The Latin alphabet looks pretty popular nowadays :-). Everything
evolves, including languages. And there are dead ends within them
which just die out - e.g. roman numbers. Can't see much future in
any hieroglyph based language though, inventing a symbol for each
word has been demonstrated to be a bad idea by history.

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Thread

How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-23 00:07 +0200
  Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Clifford Heath <no.spam@please.net> - 2021-10-23 13:40 +1100
  Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-22 22:09 -0700
    Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-23 22:12 +0200
      Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-23 15:59 -0700
  Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-23 18:09 +0200
    Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-23 22:49 +0200
      Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-24 13:02 +0200
        Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-24 17:39 +0200
          Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-24 18:37 +0200
    Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-25 20:15 +0200
      Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-25 20:54 +0200
      Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Richard Damon <Richard@Damon-Family.org> - 2021-10-25 20:31 -0400
  Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Johann Klammer <klammerj@NOSPAM.a1.net> - 2021-10-24 12:39 +0200
    Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-24 14:14 +0300
      Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-24 12:54 -0700
        Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-24 23:27 +0300
          Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-24 14:08 -0700
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-25 00:50 +0300
              Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-24 15:47 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-25 02:32 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-24 18:34 -0700
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-25 09:41 +0200
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 10:56 +0300
              Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 01:19 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 11:52 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 02:50 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-25 13:49 +0200
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 15:16 +0300
          Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 11:09 +0300
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 01:28 -0700
              Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 12:06 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 02:35 -0700
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-25 16:04 +0300
              Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 18:34 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 10:43 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-25 20:53 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 11:02 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-25 19:52 +0200
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 11:10 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 21:33 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-25 22:09 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-10-25 22:53 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Dimiter_Popoff <dp@tgi-sci.com> - 2021-10-25 23:02 +0300
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-26 00:05 +0200
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on pozz <pozzugno@gmail.com> - 2021-10-25 23:46 +0200
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-25 20:58 +0200
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Clifford Heath <no.spam@please.net> - 2021-10-26 08:43 +1100
        Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on antispam@math.uni.wroc.pl - 2021-10-25 21:32 +0000
          Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-25 15:24 -0700
            Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on antispam@math.uni.wroc.pl - 2021-10-27 00:20 +0000
              Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-26 17:52 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on antispam@math.uni.wroc.pl - 2021-10-27 05:22 +0000
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-29 15:36 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on antispam@math.uni.wroc.pl - 2021-10-31 22:54 +0000
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-10-31 20:37 -0700
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on antispam@math.uni.wroc.pl - 2021-11-11 04:34 +0000
                Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on Don Y <blockedofcourse@foo.invalid> - 2021-11-19 16:21 -0700
      Re: How to write a simple driver in bare metal systems: volatile, memory barrier, critical sections and so on David Brown <david.brown@hesbynett.no> - 2021-10-25 08:57 +0200

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