linux-kernel - Re: [PATCH 12/15] usb: serial: ipw: use usb_control_msg

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Message-ID: <X8oPEybfSt/pOrqY@localhost>
Date:   Fri, 4 Dec 2020 11:27:31 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Himadri Pandya <himadrispandya@...il.com>
Cc:     johan@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH 12/15] usb: serial: ipw: use usb_control_msg_send()

On Wed, Nov 04, 2020 at 12:17:00PM +0530, Himadri Pandya wrote:
> The new usb_control_msg_send() nicely wraps usb_control_msg() with proper
> error check. Hence use the wrapper instead of calling usb_control_msg()
> directly.
> 
> Signed-off-by: Himadri Pandya <himadrispandya@...il.com>
> ---
>  drivers/usb/serial/ipw.c | 107 +++++++++++++--------------------------
>  1 file changed, 36 insertions(+), 71 deletions(-)
> 
> diff --git a/drivers/usb/serial/ipw.c b/drivers/usb/serial/ipw.c
> index d04c7cc5c1c2..3c3895b4dff8 100644
> --- a/drivers/usb/serial/ipw.c
> +++ b/drivers/usb/serial/ipw.c
> @@ -134,26 +134,16 @@ static int ipw_open(struct tty_struct *tty, struct usb_serial_port *port)
>  	struct usb_device *udev = port->serial->dev;
>  	struct device *dev = &port->dev;
>  	u8 buf_flow_static[16] = IPW_BYTES_FLOWINIT;
> -	u8 *buf_flow_init;
>  	int result;
>  
> -	buf_flow_init = kmemdup(buf_flow_static, 16, GFP_KERNEL);
> -	if (!buf_flow_init)
> -		return -ENOMEM;
> -
>  	/* --1: Tell the modem to initialize (we think) From sniffs this is
>  	 *	always the first thing that gets sent to the modem during
>  	 *	opening of the device */
>  	dev_dbg(dev, "%s: Sending SIO_INIT (we guess)\n", __func__);
> -	result = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
> -			 IPW_SIO_INIT,
> -			 USB_TYPE_VENDOR | USB_RECIP_INTERFACE | USB_DIR_OUT,
> -			 0,
> -			 0, /* index */
> -			 NULL,
> -			 0,
> -			 100000);
> -	if (result < 0)
> +	result = usb_control_msg_send(udev, 0, IPW_SIO_INIT, USB_TYPE_VENDOR |
> +				      USB_RECIP_INTERFACE | USB_DIR_OUT, 0,
> +				      0,  NULL, 0, 100000, GFP_KERNEL);

Try to keep the existing indentation style and also avoid breaking the
request argument (USB_TYPE_VENDOR | ...) over multiple lines.

> +	if (result)
>  		dev_err(dev, "Init of modem failed (error = %d)\n", result);
>  
>  	/* reset the bulk pipes */
> @@ -166,31 +156,22 @@ static int ipw_open(struct tty_struct *tty, struct usb_serial_port *port)
>  
>  	/*--3: Tell the modem to open the floodgates on the rx bulk channel */
>  	dev_dbg(dev, "%s:asking modem for RxRead (RXBULK_ON)\n", __func__);
> -	result = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
> -			 IPW_SIO_RXCTL,
> -			 USB_TYPE_VENDOR | USB_RECIP_INTERFACE | USB_DIR_OUT,
> -			 IPW_RXBULK_ON,
> -			 0, /* index */
> -			 NULL,
> -			 0,
> -			 100000);
> -	if (result < 0)
> +	result = usb_control_msg_send(udev, 0, IPW_SIO_RXCTL, USB_TYPE_VENDOR |
> +				      USB_RECIP_INTERFACE | USB_DIR_OUT,
> +				      IPW_RXBULK_ON, 0, NULL, 0, 100000,
> +				      GFP_KERNEL);
> +	if (result)
>  		dev_err(dev, "Enabling bulk RxRead failed (error = %d)\n", result);
>  
>  	/*--4: setup the initial flowcontrol */
> -	dev_dbg(dev, "%s:setting init flowcontrol (%s)\n", __func__, buf_flow_init);
> -	result = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
> -			 IPW_SIO_HANDFLOW,
> -			 USB_TYPE_VENDOR | USB_RECIP_INTERFACE | USB_DIR_OUT,
> -			 0,
> -			 0,
> -			 buf_flow_init,
> -			 0x10,
> -			 200000);
> -	if (result < 0)
> +	dev_dbg(dev, "%s:setting init flowcontrol (%s)\n", __func__, buf_flow_static);
> +	result = usb_control_msg_send(udev, 0, IPW_SIO_HANDFLOW,
> +				      USB_TYPE_VENDOR | USB_RECIP_INTERFACE |
> +				      USB_DIR_OUT, 0, 0, &buf_flow_static, 0x10,
> +				      200000, GFP_KERNEL);
> +	if (result)
>  		dev_err(dev, "initial flowcontrol failed (error = %d)\n", result);

Note that sending a short control message is always an error so there's
nothing wrong with the current errors checks.

In fact, since all but this control request lacks a data stage, I'd just
leave this one as is as well.

Johan