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Date:   Sat, 15 Jun 2019 14:43:09 +0300
From:   Andy Shevchenko <>
To:     Serge Semin <>
Cc:     Jean Delvare <>,
        Peter Korsgaard <>,
        Peter Rosin <>,
        Serge Semin <>,
        Mika Westerberg <>,
        Andy Shevchenko <>,
        Linus Walleij <>,
        linux-i2c <>,
        Linux Kernel Mailing List <>
Subject: Re: [PATCH] i2c: mux-gpio: Use "mux" con_id to find channel GPIOs

On Sat, Jun 15, 2019 at 12:51 AM Serge Semin <> wrote:
> Recent patch - ("i2c: mux/i801: Switch to use descriptor passing")
> altered the i2c-mux-gpio driver to use the GPIO-descriptor
> based interface to find and request the GPIOs then being utilized
> to select and deselect the channels of GPIO-driven i2c-muxes. Even
> though the proposed modification was correct for the platform_data-based
> systems, it was invalid for the OF-based ones and caused the kernel
> to crash at the driver probe procedure. There were two problems with
> that modification. First of all the gpiod_count() and gpiod_get_index()
> were called with NULL con_id.

I always thought that this means "count me all GPIO's for this device
despite their names" and "get me GPIO by index despite it's name".
What's went wrong?

> Due to this the methods couldn't find
> the "mux-gpios" OF-properties and returned the -ENOENT error. Secondly
> the return value of gpiod_count() wasn't checked for being negative,
> which in case of an error caused the driver to crash. This patch
> is intended to fix the described problems.

With Best Regards,
Andy Shevchenko

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