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From: Eric Anholt <eric@anholt.net>
To: Linus Walleij <linus.walleij@linaro.org>,
        Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [PATCH 27/32] gpio: Add support for the FXL6408 GPIO expander.
In-Reply-To: <CACRpkdax3AmnprT48zL7J92ddMvLYeRXi9OrQK_JrBT8_zZQoA@mail.gmail.com>
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Date: Thu, 09 Jun 2016 10:22:27 -0700
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Linus Walleij <linus.walleij@linaro.org> writes:

> On Wed, Jun 1, 2016 at 11:43 PM, Gerd Hoffmann <kraxel@redhat.com> wrote:
>
>> +#define FXL6408_OUTPUT                 0x05
>> +/* Bits here make the output High-Z, instead of the OUTPUT value. */
>> +#define FXL6408_OUTPUT_HIGH_Z          0x07
> (...)
>> +       /* Disable High-Z of outputs, so that our OUTPUT updates
>> +        * actually take effect.
>> +        */
>> +       i2c_smbus_write_byte_data(client, FXL6408_OUTPUT_HIGH_Z, 0);
>
> High-Z is probably the same as open drain right? And if not open drain,
> it is push-pull.
>
> So you want to implement .set_single_ended() for configuring the lines in
> "high-z", i.e. open drain output mode.

I'll keep this in mind for whenever I end up writing my next GPIO
driver, but this one is dead for now (not actually usable because of the
closed firmware).

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