Re: [Linux-kernel-mentees] [PATCH 4/4] net: rndis_host: use usb_control_msg_recv() and usb_control_msg_send()

[Himadri Pandya <himadrispandya@gmail.com>]

On Wed, Sep 23, 2020 at 3:52 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Sep 23, 2020 at 02:35:19PM +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 <himadrispandya@gmail.com>
> > ---
> >  drivers/net/usb/rndis_host.c | 44 ++++++++++++++----------------------
> >  1 file changed, 17 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
> > index 6fa7a009a24a..30fc4a7183d3 100644
> > --- a/drivers/net/usb/rndis_host.c
> > +++ b/drivers/net/usb/rndis_host.c
> > @@ -113,14 +113,13 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
> >               buf->request_id = (__force __le32) xid;
> >       }
> >       master_ifnum = info->control->cur_altsetting->desc.bInterfaceNumber;
> > -     retval = usb_control_msg(dev->udev,
> > -             usb_sndctrlpipe(dev->udev, 0),
> > -             USB_CDC_SEND_ENCAPSULATED_COMMAND,
> > -             USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> > -             0, master_ifnum,
> > -             buf, le32_to_cpu(buf->msg_len),
> > -             RNDIS_CONTROL_TIMEOUT_MS);
> > -     if (unlikely(retval < 0 || xid == 0))
> > +     retval = usb_control_msg_send(dev->udev, 0,
> > +                                   USB_CDC_SEND_ENCAPSULATED_COMMAND,
> > +                                   USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> > +                                   0, master_ifnum, buf,
> > +                                   le32_to_cpu(buf->msg_len),
> > +                                   RNDIS_CONTROL_TIMEOUT_MS);
> > +     if (unlikely(xid == 0))
> >               return retval;
> >
> >       /* Some devices don't respond on the control channel until
> > @@ -139,14 +138,11 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
> >       /* Poll the control channel; the request probably completed immediately */
> >       rsp = le32_to_cpu(buf->msg_type) | RNDIS_MSG_COMPLETION;
> >       for (count = 0; count < 10; count++) {
> > -             memset(buf, 0, CONTROL_BUFFER_SIZE);
> > -             retval = usb_control_msg(dev->udev,
> > -                     usb_rcvctrlpipe(dev->udev, 0),
> > -                     USB_CDC_GET_ENCAPSULATED_RESPONSE,
> > -                     USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> > -                     0, master_ifnum,
> > -                     buf, buflen,
> > -                     RNDIS_CONTROL_TIMEOUT_MS);
> > +             retval = usb_control_msg_recv(dev->udev, 0,
> > +                                           USB_CDC_GET_ENCAPSULATED_RESPONSE,
> > +                                           USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> > +                                           0, master_ifnum, buf, buflen,
> > +                                           RNDIS_CONTROL_TIMEOUT_MS);
> >               if (likely(retval >= 8)) {
>
> retval here is never going to be positive, right?  So I don't think this
> patch is correct :(
>

Yes :(.

> >                       msg_type = le32_to_cpu(buf->msg_type);
> >                       msg_len = le32_to_cpu(buf->msg_len);
> > @@ -178,17 +174,11 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
> >                               msg->msg_type = cpu_to_le32(RNDIS_MSG_KEEPALIVE_C);
> >                               msg->msg_len = cpu_to_le32(sizeof *msg);
> >                               msg->status = cpu_to_le32(RNDIS_STATUS_SUCCESS);
> > -                             retval = usb_control_msg(dev->udev,
> > -                                     usb_sndctrlpipe(dev->udev, 0),
> > -                                     USB_CDC_SEND_ENCAPSULATED_COMMAND,
> > -                                     USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> > -                                     0, master_ifnum,
> > -                                     msg, sizeof *msg,
> > -                                     RNDIS_CONTROL_TIMEOUT_MS);
> > -                             if (unlikely(retval < 0))
> > -                                     dev_dbg(&info->control->dev,
> > -                                             "rndis keepalive err %d\n",
> > -                                             retval);
> > +                             retval = usb_control_msg_send(dev->udev, 0,
> > +                                                           USB_CDC_SEND_ENCAPSULATED_COMMAND,
> > +                                                           USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> > +                                                           0, master_ifnum, msg, sizeof(*msg),
> > +                                                           RNDIS_CONTROL_TIMEOUT_MS);
>
> You lost the error message that the previous call had if something went
> wrong.  Don't know if it's really needed, but there's no reason to
> remove it here.
>

The wrapper returns the error so thought that might work instead. But
yes, the old msg is better.

Anyways, this series is dropped :).

Thanks for the review,
Himadri

> thanks,
>
> greg k-h
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