linux-kernel - Re: [PATCH v2 6/7] drm/bridge: anx7625: Register Type-C mode switches

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Message-ID: <28135a2f-bf02-fd0b-e881-0ce9d68bd764@collabora.com>
Date:   Wed, 15 Jun 2022 10:45:31 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Prashant Malani <pmalani@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        heikki.krogerus@...ux.intel.com,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>, Jonas Karlman <jonas@...boo.se>,
        swboyd@...omium.org, Pin-Yen Lin <treapking@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime@...no.tech>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Xin Ji <xji@...logixsemi.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robert Foss <robert.foss@...aro.org>,
        José Expósito <jose.exposito89@...il.com>
Subject: Re: [PATCH v2 6/7] drm/bridge: anx7625: Register Type-C mode switches

Il 14/06/22 18:57, Prashant Malani ha scritto:
> On Tue, Jun 14, 2022 at 1:18 AM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>>
>> Il 09/06/22 20:09, Prashant Malani ha scritto:
>>> When the DT node has "switches" available, register a Type-C mode-switch
>>> for each listed "switch". This allows the driver to receive state
>>> information about what operating mode a Type-C port and its connected
>>> peripherals are in, as well as status information (like VDOs) related to
>>> that state.
>>>
>>> The callback function is currently a stub, but subsequent patches will
>>> implement the required functionality.
>>>
>>> Signed-off-by: Prashant Malani <pmalani@...omium.org>
>>> ---
>>>
>>> Changes since v2:
>>> - No changes.
>>>
>>>    drivers/gpu/drm/bridge/analogix/anx7625.c | 73 +++++++++++++++++++++++
>>>    drivers/gpu/drm/bridge/analogix/anx7625.h |  6 ++
>>>    2 files changed, 79 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
>>> index 07ed44c6b839..d41a21103bd3 100644
>>> --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
>>> +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
>>> @@ -15,6 +15,7 @@
>>>    #include <linux/regulator/consumer.h>
>>>    #include <linux/slab.h>
>>>    #include <linux/types.h>
>>> +#include <linux/usb/typec_mux.h>
>>>    #include <linux/workqueue.h>
>>>
>>>    #include <linux/of_gpio.h>
>>> @@ -2581,9 +2582,59 @@ static void anx7625_runtime_disable(void *data)
>>>        pm_runtime_disable(data);
>>>    }
>>>
>>> +static int anx7625_typec_mux_set(struct typec_mux_dev *mux,
>>> +                              struct typec_mux_state *state)
>>> +{
>>> +     return 0;
>>> +}
>>> +
>>> +static int anx7625_register_mode_switch(struct device *dev, struct device_node *node,
>>> +                                     struct anx7625_data *ctx)
>>> +{
>>> +     struct anx7625_port_data *port_data;
>>> +     struct typec_mux_desc mux_desc = {};
>>> +     char name[32];
>>> +     u32 port_num;
>>> +     int ret;
>>> +
>>> +     ret = of_property_read_u32(node, "reg", &port_num);
>>> +     if (ret)
>>> +             return ret;
>>> +
>>> +     if (port_num >= ctx->num_typec_switches) {
>>> +             dev_err(dev, "Invalid port number specified: %d\n", port_num);
>>> +             return -EINVAL;
>>> +     }
>>> +
>>> +     port_data = &ctx->typec_ports[port_num];
>>> +     port_data->ctx = ctx;
>>> +     mux_desc.fwnode = &node->fwnode;
>>> +     mux_desc.drvdata = port_data;
>>> +     snprintf(name, sizeof(name), "%s-%u", node->name, port_num);
>>> +     mux_desc.name = name;
>>> +     mux_desc.set = anx7625_typec_mux_set;
>>> +
>>> +     port_data->typec_mux = typec_mux_register(dev, &mux_desc);
>>> +     if (IS_ERR(port_data->typec_mux)) {
>>> +             ret = PTR_ERR(port_data->typec_mux);
>>> +             dev_err(dev, "Mode switch register for port %d failed: %d", port_num, ret);
>>> +     }
>>
>> Please return 0 at the end of this function.
>>
>>          if (IS_ERR(....)) {
>>                  ......code......
>>                  return ret;
>>          }
>>
>>          return 0;
>> }
> 
> May I ask why? We're not missing any return paths. I would rather we
> keep it as is (which has the valid return value).
> 

I know that you're not missing any return paths.

That's only because the proposed one is a common pattern in the kernel
and it's only for consistency.

Regards,
Angelo