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 <20190219193027.13882-1-jbroadus@gmail.com>
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From:   Jim Broadus <jbroadus@gmail.com>
Date:   Tue, 19 Feb 2019 11:32:43 -0800
Message-ID: <CAKgEEwtTJWTAdYF1FAZC_zMXaPu_fJTqaAiLHQK6_6K63VHEkg@mail.gmail.com>
Subject: Re: [PATCH] i2c: Allow recovery of the initial IRQ by an I2C client device.
To:     Charles Keepax <ckeepax@opensource.cirrus.com>, wsa@the-dreams.de,
        linux-i2c@vger.kernel.org,
        Linux Kernel <linux-kernel@vger.kernel.org>
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Apologies.. This should have been marked v2.

On Tue, Feb 19, 2019 at 11:30 AM Jim Broadus <jbroadus@gmail.com> wrote:
>
> A previous change allowed I2C client devices to discover new IRQs upon
> reprobe by clearing the IRQ in i2c_device_remove. However, if an IRQ was
> assigned in i2c_new_device, that information is lost.
>
> For example, the touchscreen and trackpad devices on a Dell Inspiron laptop
> are I2C devices whose IRQs are defined by ACPI extended IRQ types. The
> client device structures are initialized during an ACPI walk. After
> removing the i2c_hid device, modprobe fails.
>
> This change caches the initial IRQ value in i2c_new_device and then resets
> the client device IRQ to the initial value in i2c_device_remove.
>
> Fixes: 6f108dd70d30 ("i2c: Clear client->irq in i2c_device_remove")
> Signed-off-by: Jim Broadus <jbroadus@gmail.com>
> ---
>  drivers/i2c/i2c-core-base.c | 9 +++++----
>  include/linux/i2c.h         | 1 +
>  2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 28460f6a60cc..af87a16ac3a5 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -430,7 +430,7 @@ static int i2c_device_remove(struct device *dev)
>         dev_pm_clear_wake_irq(&client->dev);
>         device_init_wakeup(&client->dev, false);
>
> -       client->irq = 0;
> +       client->irq = client->init_irq;
>
>         return status;
>  }
> @@ -741,10 +741,11 @@ i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
>         client->flags = info->flags;
>         client->addr = info->addr;
>
> -       client->irq = info->irq;
> -       if (!client->irq)
> -               client->irq = i2c_dev_irq_from_resources(info->resources,
> +       client->init_irq = info->irq;
> +       if (!client->init_irq)
> +               client->init_irq = i2c_dev_irq_from_resources(info->resources,
>                                                          info->num_resources);
> +       client->irq = client->init_irq;
>
>         strlcpy(client->name, info->type, sizeof(client->name));
>
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 65b4eaed1d96..7e748648c7d3 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -333,6 +333,7 @@ struct i2c_client {
>         char name[I2C_NAME_SIZE];
>         struct i2c_adapter *adapter;    /* the adapter we sit on        */
>         struct device dev;              /* the device structure         */
> +       int init_irq;                   /* irq set at initialization    */
>         int irq;                        /* irq issued by device         */
>         struct list_head detected;
>  #if IS_ENABLED(CONFIG_I2C_SLAVE)
> --
> 2.20.1
>