linux-kernel - Re: [PATCH v5] usb: common: usb-conn-gpio: Set last role to unknown before initial detection

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Date:   Thu, 25 May 2023 17:34:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Prashanth K <quic_prashk@...cinc.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] usb: common: usb-conn-gpio: Set last role to unknown
 before initial detection

On Thu, May 25, 2023 at 02:23:45PM +0530, Prashanth K wrote:
> Currently if we bootup a device without cable connected, then
> usb-conn-gpio won't call set_role() since last_role is same as
> current role. This happens because during probe last_role gets
> initialised to zero.
> 
> To avoid this, added a new constant in enum usb_role, last_role
> is set to USB_ROLE_UNKNOWN before performing initial detection.
> 
> While at it, also handle default case for the usb_role switch
> in cdns3 to avoid build warnings.
> 
> Fixes: 4602f3bff266 ("usb: common: add USB GPIO based connection detection driver")
> Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
> v5: Update commit text to mention the changes made in cdns3 driver.
> v4: Added Reviewed-by tag.
> v3: Added a default case in drivers/usb/cdns3/core.c as pointed out by
>     the test robot.
> v2: Added USB_ROLE_UNKNWON to enum usb_role.
> 
>  drivers/usb/cdns3/core.c           | 2 ++
>  drivers/usb/common/usb-conn-gpio.c | 3 +++
>  include/linux/usb/role.h           | 1 +
>  3 files changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
> index dbcdf3b..69d2921 100644
> --- a/drivers/usb/cdns3/core.c
> +++ b/drivers/usb/cdns3/core.c
> @@ -252,6 +252,8 @@ static enum usb_role cdns_hw_role_state_machine(struct cdns *cdns)
>  		if (!vbus)
>  			role = USB_ROLE_NONE;
>  		break;
> +	default:
> +		break;

No error if this happens?

>  	}
>  
>  	dev_dbg(cdns->dev, "role %d -> %d\n", cdns->role, role);
> diff --git a/drivers/usb/common/usb-conn-gpio.c b/drivers/usb/common/usb-conn-gpio.c
> index e20874c..30bdb81 100644
> --- a/drivers/usb/common/usb-conn-gpio.c
> +++ b/drivers/usb/common/usb-conn-gpio.c
> @@ -257,6 +257,9 @@ static int usb_conn_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, info);
>  	device_set_wakeup_capable(&pdev->dev, true);
>  
> +	/* Set last role to unknown before performing the initial detection */
> +	info->last_role = USB_ROLE_UNKNOWN;

Shouldn't last_role have already been set to 0?  If so, why not just
have this enum value be 0?


> +
>  	/* Perform initial detection */
>  	usb_conn_queue_dwork(info, 0);
>  
> diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
> index b5deafd..221d462 100644
> --- a/include/linux/usb/role.h
> +++ b/include/linux/usb/role.h
> @@ -8,6 +8,7 @@
>  struct usb_role_switch;
>  
>  enum usb_role {
> +	USB_ROLE_UNKNOWN = -1,

Why is this explicitly set to a value?  What is magic about -1?  Why not
0x42?  Or something else?  Or as I mention above, 0?

thanks,

greg k-h