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

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Date:   Wed, 15 Jun 2022 10:00:48 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
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

On Wed, Jun 15, 2022 at 1:45 AM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> 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.

Thanks for the additional details. Since this isn't addressing any
specific bug, and I
notice varied usages of "return ret" in this file itself [1][2], I'd
prefer keeping it as is.

[1]: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix/anx7625.c#L296
[2]: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix/anx7625.c#L436

>
> Regards,
> Angelo
>