Re: [PATCH v3 2/2] USB: serial: cp210x: use usb_control_msg_recv() and usb_control_msg_send()

[Himadri Pandya]

On Wed, Oct 27, 2021 at 3:18 PM Johan Hovold <johan@xxxxxxxxxx> wrote:
>
> On Fri, Oct 01, 2021 at 08:57:20AM +0200, Himadri Pandya wrote:
> > The new wrapper functions for usb_control_msg() can accept data from
> > stack and treat short reads as error. Hence use the wrappers functions.
> > Please note that because of this change, cp210x_read_reg_block() will no
> > longer log the length of short reads.
> >
> > Signed-off-by: Himadri Pandya <himadrispandya@xxxxxxxxx>
> > ---
> > Changes in v3:
> >  - Rephrase the commit message
> >  - Explicitly mention that short reads don't log length now
> >
> > Changes in v2:
> >  - Drop unrelated style fixes
>
> This looks good now, but I did do some minor style changes described
> below.
>
> > ---
> >  drivers/usb/serial/cp210x.c | 106 ++++++++++--------------------------
> >  1 file changed, 30 insertions(+), 76 deletions(-)
> >
> > diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> > index 189279869a8b..3c3ca46b0b82 100644
> > --- a/drivers/usb/serial/cp210x.c
> > +++ b/drivers/usb/serial/cp210x.c
> > @@ -631,29 +631,19 @@ 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)
> > -             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_GET_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);
>
> The indentation style of this driver is a bit inconsistent but there's
> no need to change to the open-parenthesis alignment style when you can
> avoid it (it's mostly just "checkpacth.pl --subjective" that insists on
> it).
>
> Indenting continuation lines two tabs is just fine and avoids excessive
> indentation and having to realign arguments when symbol names change.
>

Thanks for clearing this up. I followed the checkpatch suggestion in
v2 and then came back to the original style of the driver in v3.
Feeling the extra spaces to match the indentation wasn't really fun.

> > +     if (result) {
> >               dev_err(&port->dev, "failed get req 0x%x size %d status: %d\n",
> >                               req, bufsize, result);
> > -             if (result >= 0)
> > -                     result = -EIO;
> >       }
> >
> > -     kfree(dmabuf);
> > -
> >       return result;
>
> I changed this to explicit zero and return an error above instead.

Okay.

>
> > @@ -952,27 +915,18 @@ static int cp210x_get_tx_queue_byte_count(struct usb_serial_port *port,
> >  {
> >       struct usb_serial *serial = port->serial;
> >       struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
> > -     struct cp210x_comm_status *sts;
> > +     struct cp210x_comm_status sts;
> >       int result;
> >
> > -     sts = kmalloc(sizeof(*sts), GFP_KERNEL);
> > -     if (!sts)
> > -             return -ENOMEM;
> > -
> > -     result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
> > -                     CP210X_GET_COMM_STATUS, REQTYPE_INTERFACE_TO_HOST,
> > -                     0, port_priv->bInterfaceNumber, sts, sizeof(*sts),
> > -                     USB_CTRL_GET_TIMEOUT);
> > -     if (result == sizeof(*sts)) {
> > -             *count = le32_to_cpu(sts->ulAmountInOutQueue);
> > -             result = 0;
> > -     } else {
> > +     result = usb_control_msg_recv(serial->dev, 0, CP210X_GET_COMM_STATUS,
> > +                                   REQTYPE_INTERFACE_TO_HOST, 0,
> > +                                   port_priv->bInterfaceNumber, &sts,
> > +                                   sizeof(sts), USB_CTRL_GET_TIMEOUT,
> > +                                   GFP_KERNEL);
> > +     if (result == 0)
> > +             *count = le32_to_cpu(sts.ulAmountInOutQueue);
> > +     else
> >               dev_err(&port->dev, "failed to get comm status: %d\n", result);
> > -             if (result >= 0)
> > -                     result = -EIO;
> > -     }
> > -
> > -     kfree(sts);
>
> The above is now also better handled with an explicit error check and
> early return and the doing the *count assignment in the success path.
>

Yes.

> >
> >       return result;
> >  }
>
> Now applied with the above changes. The result is here:
>
>         https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git/commit/?h=usb-next&id=f5cfbecb0a162319464c9408420282d22ed69721
>
> Johan

Thank you.

Regards,
Himadri