linux-kernel - Re: [RFC PATCH 4/5] gnss: ubx: add support for the reset gpio

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Date:   Tue, 20 Jun 2023 12:05:31 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc:     linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 4/5] gnss: ubx: add support for the reset gpio

On Tue, Jun 20, 2023 at 11:41:39AM +0200, Wolfram Sang wrote:
> 
> > But can you elaborate on the "disappearing" bit? How exactly does it
> > "disappear" when the gnss0 device is *not* opened?
> 
> When you send an I2C message with the address of the device, it usually
> ACKs it to say "Hi, I am here". When the ublox device is in reset state,
> it does not ACK its address. So, tools like "i2cdetect" will not report
> the device as "someone is listening there".

Ah, ok, so you used it to verify that reset is working as intended.

Rereading the commit message now it makes more sense, I guess I was
thrown off by the reference to I2C. Perhaps adding a sentence or two
about the alternate interface and using it as a means of verification
would make things a bit more clear.

Johan

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