linux-kernel - Re: [PATCH v3 3/3] platform/chrome: typec: Register port partner

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Date:   Tue, 14 Apr 2020 16:08:32 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Prashant Malani <pmalani@...omium.org>,
        linux-kernel@...r.kernel.org
Cc:     heikki.krogerus@...ux.intel.com, Jon Flatley <jflat@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH v3 3/3] platform/chrome: typec: Register port partner

Hi Prashant,

Thank you for your patch.

On 10/4/20 2:23, Prashant Malani wrote:
> Register (and unregister) the port partner when a connect (and
> disconnect) is detected.
> 
> Co-developed-by: Jon Flatley <jflat@...omium.org>
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
> 
> Changes in v3:
> - No changes.
> 
> Changes in v2:
> - Fixed error pointer return value.
> 
>  drivers/platform/chrome/cros_ec_typec.c | 48 +++++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index 56ded09a60ffb..304e0b20f279b 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -22,6 +22,9 @@ struct cros_typec_port {
>  	struct typec_port *port;
>  	/* Initial capabilities for the port. */
>  	struct typec_capability caps;
> +	struct typec_partner *partner;
> +	/* Port partner PD identity info. */
> +	struct usb_pd_identity p_identity;
>  };
>  
>  /* Platform-specific data for the Chrome OS EC Type C controller. */
> @@ -190,6 +193,30 @@ static int cros_typec_ec_command(struct cros_typec_data *typec,
>  	return ret;
>  }
>  
> +static int cros_typec_add_partner(struct cros_typec_data *typec, int port_num,
> +				  bool pd_en)
> +{
> +	struct cros_typec_port *port = typec->ports[port_num];
> +	struct typec_partner_desc p_desc = {
> +		.usb_pd = pd_en,
> +	};
> +	int ret = 0;
> +
> +	/*
> +	 * Fill an initial PD identity, which will then be updated with info
> +	 * from the EC.
> +	 */
> +	p_desc.identity = &port->p_identity;
> +
> +	port->partner = typec_register_partner(port->port, &p_desc);
> +	if (IS_ERR_OR_NULL(port->partner)) {
> +		ret = PTR_ERR(port->partner);

If you're checking for IS_ERR_OR_NULL that means that port->partner can be NULL,
so PTR_ERR(NULL) is 0 returning something that you don't really want.

But looking at the typec_register_partner, NULL is not an option as returns a
handle to the partner on success or ERR_PTR on failure. So, the code should just do:

if (IS_ERR(port->partner))
    return PTR_ERR(port->partner);

And AFAICS you don't need to set port->partner to NULL.

Can you double check this?

Thanks,
 Enric

> +		port->partner = NULL;
> +	}
> +
> +	return ret;
> +}
> +
>  static void cros_typec_set_port_params_v0(struct cros_typec_data *typec,
>  		int port_num, struct ec_response_usb_pd_control *resp)
>  {
> @@ -212,6 +239,8 @@ static void cros_typec_set_port_params_v1(struct cros_typec_data *typec,
>  {
>  	struct typec_port *port = typec->ports[port_num]->port;
>  	enum typec_orientation polarity;
> +	bool pd_en;
> +	int ret;
>  
>  	if (!(resp->enabled & PD_CTRL_RESP_ENABLED_CONNECTED))
>  		polarity = TYPEC_ORIENTATION_NONE;
> @@ -226,6 +255,25 @@ static void cros_typec_set_port_params_v1(struct cros_typec_data *typec,
>  			TYPEC_SOURCE : TYPEC_SINK);
>  	typec_set_vconn_role(port, resp->role & PD_CTRL_RESP_ROLE_VCONN ?
>  			TYPEC_SOURCE : TYPEC_SINK);
> +
> +	/* Register/remove partners when a connect/disconnect occurs. */
> +	if (resp->enabled & PD_CTRL_RESP_ENABLED_CONNECTED) {
> +		if (typec->ports[port_num]->partner)
> +			return;
> +
> +		pd_en = resp->enabled & PD_CTRL_RESP_ENABLED_PD_CAPABLE;
> +		ret = cros_typec_add_partner(typec, port_num, pd_en);
> +		if (!ret)
> +			dev_warn(typec->dev,
> +				 "Failed to register partner on port: %d\n",
> +				 port_num);
> +	} else {
> +		if (!typec->ports[port_num]->partner)
> +			return;
> +
> +		typec_unregister_partner(typec->ports[port_num]->partner);
> +		typec->ports[port_num]->partner = NULL;
> +	}
>  }
>  
>  static int cros_typec_port_update(struct cros_typec_data *typec, int port_num)
>