Re: [Linux-kernel-mentees] [PATCH 04/15] usb: serial: cp210x: use usb_control_msg_recv() and usb_control_msg_send()

[Johan Hovold <johan@kernel.org>]

On Wed, Nov 04, 2020 at 12:16:52PM +0530, Himadri Pandya wrote:
> The new usb_control_msg_recv() and usb_control_msg_send() nicely wraps
> usb_control_msg() with proper error check. Hence use the wrappers
> instead of calling usb_control_msg() directly.

This too is a good example of when the new helpers can be used, but
please mention the transfer buffers here are that is the primary reason.

> Signed-off-by: Himadri Pandya <himadrispandya@gmail.com>
> ---
>  drivers/usb/serial/cp210x.c | 148 ++++++++++--------------------------
>  1 file changed, 42 insertions(+), 106 deletions(-)
> 
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index d0c05aa8a0d6..29436ab392e8 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -555,31 +555,15 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
>  {
>  	struct usb_serial *serial = port->serial;
>  	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
> -	void *dmabuf;
>  	int result;
>  
> -	dmabuf = kmalloc(bufsize, GFP_KERNEL);
> -	if (!dmabuf) {
> -		/*
> -		 * FIXME Some callers don't bother to check for error,
> -		 * at least give them consistent junk until they are fixed
> -		 */
> -		memset(buf, 0, bufsize);
> -		return -ENOMEM;
> -	}
> -
> -	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
> -			req, REQTYPE_INTERFACE_TO_HOST, 0,
> -			port_priv->bInterfaceNumber, dmabuf, bufsize,
> -			USB_CTRL_SET_TIMEOUT);
> -	if (result == bufsize) {
> -		memcpy(buf, dmabuf, bufsize);
> -		result = 0;
> -	} else {
> +	result = usb_control_msg_recv(serial->dev, 0, req,
> +				      REQTYPE_INTERFACE_TO_HOST, 0,
> +				      port_priv->bInterfaceNumber, buf, bufsize,
> +				      USB_CTRL_SET_TIMEOUT, GFP_KERNEL);

Please keep the existing indentation style. That way you don't need to
change the middle-two argument lines just to align the arguments.

> +	if (result) {
>  		dev_err(&port->dev, "failed get req 0x%x size %d status: %d\n",
> -				req, bufsize, result);
> -		if (result >= 0)
> -			result = -EIO;
> +			req, bufsize, result);

Nit: This is an unrelated indentation change.

>  
>  		/*
>  		 * FIXME Some callers don't bother to check for error,
> @@ -588,8 +572,6 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
>  		memset(buf, 0, bufsize);
>  	}
>  
> -	kfree(dmabuf);
> -
>  	return result;
>  }
>  
> @@ -648,29 +630,16 @@ static int cp210x_read_u8_reg(struct usb_serial_port *port, u8 req, u8 *val)
>  static int cp210x_read_vendor_block(struct usb_serial *serial, u8 type, u16 val,
>  				    void *buf, int bufsize)
>  {
> -	void *dmabuf;
>  	int result;
>  
> -	dmabuf = kmalloc(bufsize, GFP_KERNEL);
> -	if (!dmabuf)
> -		return -ENOMEM;
> -
> -	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
> -				 CP210X_VENDOR_SPECIFIC, type, val,
> -				 cp210x_interface_num(serial), dmabuf, bufsize,
> -				 USB_CTRL_GET_TIMEOUT);
> -	if (result == bufsize) {
> -		memcpy(buf, dmabuf, bufsize);
> -		result = 0;
> -	} else {
> +	result = usb_control_msg_recv(serial->dev, 0, CP210X_VENDOR_SPECIFIC,
> +				      type, val, cp210x_interface_num(serial),
> +				      buf, bufsize, USB_CTRL_GET_TIMEOUT,
> +				      GFP_KERNEL);
> +	if (result)
>  		dev_err(&serial->interface->dev,
>  			"failed to get vendor val 0x%04x size %d: %d\n", val,
>  			bufsize, result);
> -		if (result >= 0)
> -			result = -EIO;
> -	}

Nit: Please keep the brackets around multiline single statements since
it improves readability.

Similar comments apply to the rest of the patch.

Johan
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees