linux-kernel - Re: [PATCH 08/18] staging: typec: fusb302: Add support for USB2 charger detection through extcon

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Message-ID: <9de0a2f3-7316-5a7d-d715-29e83a278844@roeck-us.net>
Date:   Sun, 6 Aug 2017 07:22:40 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Hans de Goede <hdegoede@...hat.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Sebastian Reichel <sre@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, Liam Breck <liam@...workimprov.net>,
        Tony Lindgren <tony@...mide.com>, linux-pm@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH 08/18] staging: typec: fusb302: Add support for USB2
 charger detection through extcon

On 08/06/2017 05:35 AM, Hans de Goede wrote:
> The fusb302 port-controller relies on an external device doing USB2
> charger-type detection.
> 
> The Intel Whiskey Cove PMIC with which the fusb302 is combined on some
> X86/ACPI platforms already has a charger-type detection driver which
> uses extcon to communicate the detected charger-type.
> 
> This commit uses the tcpm_get_usb2_current_limit_extcon helper to enable
> USB2 charger detection on these systems. Note that the "fcs,extcon-name"
> property name is only for kernel internal use by X86/ACPI platform code
> and as such is NOT documented in the devicetree bindings.
> 
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> ---
>   drivers/staging/typec/fusb302/fusb302.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/staging/typec/fusb302/fusb302.c b/drivers/staging/typec/fusb302/fusb302.c
> index be454b5ff6c7..1d8c9b66df2f 100644
> --- a/drivers/staging/typec/fusb302/fusb302.c
> +++ b/drivers/staging/typec/fusb302/fusb302.c
> @@ -1201,6 +1201,8 @@ static void init_tcpc_dev(struct tcpc_dev *fusb302_tcpc_dev)
>   {
>   	fusb302_tcpc_dev->init = tcpm_init;
>   	fusb302_tcpc_dev->get_vbus = tcpm_get_vbus;
> +	fusb302_tcpc_dev->get_usb2_current_limit =
> +		tcpm_get_usb2_current_limit_extcon;
>   	fusb302_tcpc_dev->set_cc = tcpm_set_cc;
>   	fusb302_tcpc_dev->get_cc = tcpm_get_cc;
>   	fusb302_tcpc_dev->set_polarity = tcpm_set_polarity;
> @@ -1685,6 +1687,7 @@ static int fusb302_probe(struct i2c_client *client,
>   	struct fusb302_chip *chip;
>   	struct i2c_adapter *adapter;
>   	struct device *dev = &client->dev;
> +	const char *name;
>   	int ret = 0;
>   	u32 val;
>   
> @@ -1717,6 +1720,19 @@ static int fusb302_probe(struct i2c_client *client,
>   	if (device_property_read_u32(dev, "fcs,operating-snk-mw", &val) == 0)
>   		chip->tcpc_config.operating_snk_mw = val;
>   
> +	/*
> +	 * Devicetree platforms should get extcon via phandle (not yet
> +	 * supported). On ACPI platforms, we get the name from a device prop.
> +	 * This device prop is for kernel internal use only and is expected
> +	 * to be set by the platform code which also registers the i2c client
> +	 * for the fusb302.
> +	 */
> +	if (device_property_read_string(dev, "fcs,extcon-name", &name) == 0) {

Those new devicetree properties need to be documented and approved by dt maintainers.

> +		chip->tcpc_dev.usb2_extcon = extcon_get_extcon_dev(name);
> +		if (!chip->tcpc_dev.usb2_extcon)

extcon_get_extcon_dev() can also return an ERR_PTR.

As before, I am not really happy typing this into tcpm via tcpc_dev.
Until we have a better solution, I would prefer for that code to stay with the fusb302
code.

> +			return -EPROBE_DEFER;
> +	}
> +
>   	ret = fusb302_debugfs_init(chip);
>   	if (ret < 0)
>   		return ret;
>