linux-kernel - Re: [PATCH v9 1/1] gpio: add sloppy logic analyzer using polling

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Date: Wed, 12 Jun 2024 18:03:20 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-renesas-soc@...r.kernel.org, Jonathan Corbet <corbet@....net>, 
	Linus Walleij <linus.walleij@...aro.org>, Kent Gibson <warthog618@...il.com>, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH v9 1/1] gpio: add sloppy logic analyzer using polling

Hi Bart,

> I really dislike drivers being called in an ambiguous way like
> "simple" or - in this case "sloppy". I understand why it is - in fact
> - sloppy but can we call it anything else? Like
> "gpio-logic-analyzer.c"?

Sure, we can if you prefer. I named it like this to make the limitations
super-clear. And even with that in place, I still got a private email
where someone wanted to build a 400MHz-RPi-based logic analyzer device
with it. Which would not only have the latency problems, but also
likely have a max sampling speed of whopping 400kHz.

> > +Note that you must provide a name for every GPIO specified. Currently a
> > +maximum of 8 probes are supported. 32 are likely possible but are not
> > +implemented yet.
> > +
> 
> What happens on non-DT systems? Can you still create an analyzer in a
> different way? Can I maybe interest you in configfs for the purpose of
> device configuration like what gpio-sim and the upcoming gpio-virtuser
> does?

Frankly, I'd like to leave this to the person needing it. I've been
working on this for way too long already and am not up to major changes
anymore. Minor stuff, okay, I'll go one or two more rounds.

The GPIO analyzer is a debug tool aimed for development boards in remote
labs, and all boards I have access to use DT. Furthermore, debugfs is nice
because it is clear there is no stable ABI. It has been useful as-is in
the past. That's what I am offering. If that's not enough, no hard
feelings, but someone else needs to continue then.

All the best,

   Wolfram

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