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

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Date: Tue, 11 Jun 2024 22:03:49 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>
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

On Mon, Jun 10, 2024 at 1:27 PM Wolfram Sang
<wsa+renesas@...g-engineering.com> wrote:
>
> This is a sloppy logic analyzer using GPIOs. It comes with a script to
> isolate a CPU for polling. While this is definitely not a production
> level analyzer, it can be a helpful first view when remote debugging.
> Read the documentation for details.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> ---

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"?

> +Setup
> +=====
> +
> +Your kernel must have CONFIG_DEBUG_FS and CONFIG_CPUSETS enabled. Ideally, your
> +runtime environment does not utilize cpusets otherwise, then isolation of a CPU
> +core is easiest. If you do need cpusets, check that helper script for the
> +sloppy logic analyzer does not interfere with your other settings.
> +
> +Tell the kernel which GPIOs are used as probes. For a Device Tree based system,
> +you need to use the following bindings. Because these bindings are only for
> +debugging, there is no official schema::
> +
> +    i2c-analyzer {
> +            compatible = "gpio-sloppy-logic-analyzer";
> +            probe-gpios = <&gpio6 21 GPIO_OPEN_DRAIN>, <&gpio6 4 GPIO_OPEN_DRAIN>;
> +            probe-names = "SCL", "SDA";
> +    };
> +
> +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?

Bart