On Wed, Nov 04, 2020 at 12:16:53PM +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.
> 
> Signed-off-by: Himadri Pandya <himadrispan...@gmail.com>
> ---
>  drivers/usb/serial/cypress_m8.c | 38 +++++++++++++++++----------------
>  1 file changed, 20 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
> index cc028601c388..4d66cab8eece 100644
> --- a/drivers/usb/serial/cypress_m8.c
> +++ b/drivers/usb/serial/cypress_m8.c
> @@ -341,20 +341,21 @@ static int cypress_serial_control(struct tty_struct 
> *tty,
>                       feature_buffer[4]);
>  
>               do {
> -                     retval = usb_control_msg(port->serial->dev,
> -                                     usb_sndctrlpipe(port->serial->dev, 0),
> -                                     HID_REQ_SET_REPORT,
> -                                     USB_DIR_OUT | USB_RECIP_INTERFACE | 
> USB_TYPE_CLASS,
> -                                     0x0300, 0, feature_buffer,
> -                                     feature_len, 500);
> +                     retval = usb_control_msg_send(port->serial->dev, 0,
> +                                                   HID_REQ_SET_REPORT,
> +                                                   USB_DIR_OUT |
> +                                                   USB_RECIP_INTERFACE |
> +                                                   USB_TYPE_CLASS, 0x0300,
> +                                                   0, feature_buffer,
> +                                                   feature_len, 500,
> +                                                   GFP_KERNEL);
>  
>                       if (tries++ >= 3)
>                               break;
>  
> -             } while (retval != feature_len &&
> -                      retval != -ENODEV);
> +             } while (retval != -ENODEV);

Here you actually break the logic; after this change the driver will
always retry as the test for success is removed.

>  
> -             if (retval != feature_len) {
> +             if (retval) {
>                       dev_err(dev, "%s - failed sending serial line settings 
> - %d\n",
>                               __func__, retval);
>                       cypress_set_dead(port);
> @@ -379,19 +380,20 @@ static int cypress_serial_control(struct tty_struct 
> *tty,
>               }
>               dev_dbg(dev, "%s - retrieving serial line settings\n", 
> __func__);
>               do {
> -                     retval = usb_control_msg(port->serial->dev,
> -                                     usb_rcvctrlpipe(port->serial->dev, 0),
> -                                     HID_REQ_GET_REPORT,
> -                                     USB_DIR_IN | USB_RECIP_INTERFACE | 
> USB_TYPE_CLASS,
> -                                     0x0300, 0, feature_buffer,
> -                                     feature_len, 500);
> +                     retval = usb_control_msg_recv(port->serial->dev, 0,
> +                                                   HID_REQ_GET_REPORT,
> +                                                   USB_DIR_IN |
> +                                                   USB_RECIP_INTERFACE |
> +                                                   USB_TYPE_CLASS, 0x0300,
> +                                                   0, feature_buffer,
> +                                                   feature_len, 500,
> +                                                   GFP_KERNEL);
>  
>                       if (tries++ >= 3)
>                               break;
> -             } while (retval != feature_len
> -                                             && retval != -ENODEV);
> +             } while (retval != -ENODEV);

Same here.

>  
> -             if (retval != feature_len) {
> +             if (retval) {
>                       dev_err(dev, "%s - failed to retrieve serial line 
> settings - %d\n",
>                               __func__, retval);
>                       cypress_set_dead(port);

As the driver is already using a DMA-able buffer and is reusing it for
every retry as well, this change is now introducing redundant memdup +
memcpy for each call.

I suggest just dropping this one.

Johan

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