linux-kernel - Re: [PATCH v3 10/12] usb: misc: trancevibrator: update to use usb_control_msg

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Message-ID: <YBGEIq/jeqySlfID@hovoldconsulting.com>
Date:   Wed, 27 Jan 2021 16:17:54 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Anant Thazhemadam <anant.thazhemadam@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 10/12] usb: misc: trancevibrator: update to use
 usb_control_msg_send()

On Wed, Jan 27, 2021 at 12:10:10AM +0530, Anant Thazhemadam wrote:
> The newer usb_control_msg_{send|recv}() API are an improvement on the
> existing usb_control_msg() as it ensures that a short read/write is treated
> as an error, data can be used off the stack, and raw usb pipes need not be
> created in the calling functions.
> For this reason, the instance of usb_control_msg() has been replaced with
> usb_control_msg_send() and the return value checking condition has also
> been modified appropriately.
> 
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
> ---
>  drivers/usb/misc/trancevibrator.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/misc/trancevibrator.c b/drivers/usb/misc/trancevibrator.c
> index a3dfc77578ea..c50807b4f4ef 100644
> --- a/drivers/usb/misc/trancevibrator.c
> +++ b/drivers/usb/misc/trancevibrator.c
> @@ -59,11 +59,11 @@ static ssize_t speed_store(struct device *dev, struct device_attribute *attr,
>  	dev_dbg(&tv->udev->dev, "speed = %d\n", tv->speed);
>  
>  	/* Set speed */
> -	retval = usb_control_msg(tv->udev, usb_sndctrlpipe(tv->udev, 0),
> +	retval = usb_control_msg_send(tv->udev, 0,
>  				 0x01, /* vendor request: set speed */
>  				 USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_OTHER,
>  				 tv->speed, /* speed value */
> -				 0, NULL, 0, USB_CTRL_GET_TIMEOUT);
> +				 0, NULL, 0, USB_CTRL_GET_TIMEOUT, GFP_KERNEL);
>  	if (retval) {
>  		tv->speed = old;
>  		dev_dbg(&tv->udev->dev, "retval = %d\n", retval);

While this patch looks correct, the new helpers doesn't really buy us
anything for (OUT) control transfers without a data stage.

Johan