Subject: Re: [PATCH 1/1] SMSC LAN9500 USB2.0 10/100 ethernet adapter driver

From: Greg KH <[email-masked]>
Date: Tue, 9 Sep 2008 07:02:24 -0700

On Tue, Sep 09, 2008 at 02:19:47PM +0100, Ben Hutchings wrote:
> On Tue, 2008-09-09 at 12:36 +0100, Steve Glendinning wrote:
> [...]
> > diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
> > new file mode 100644
> > index 0000000..60ffd90
> > --- /dev/null
> > +++ b/drivers/net/usb/smsc95xx.c
> [...]
> > +static int smsc95xx_read_reg(struct usbnet *dev, u32 index, u32 *data)
> > +{
> > +	u32 *buf = kmalloc(4, GFP_KERNEL);
> > +	int ret;
> > +
> > +	BUG_ON(!dev);
> > +
> > +	if (!buf)
> > +		return -ENOMEM;
> > +
> > +	ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
> > +		USB_VENDOR_REQUEST_READ_REGISTER,
> > +		USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
> > +		00, index, buf, 4, USB_CTRL_GET_TIMEOUT);
> > +
> > +	if (unlikely(ret < 0))
> > +		SMSC_WARNING("Failed to read register index 0x%08x", index);
> > +
> > +	le32_to_cpus(buf);
> > +	*data = *buf;
> > +	kfree(buf);
> > +
> > +	return ret;
> > +}
> 
> Why are you allocating a buffer on the heap?  What's wrong with

USB requires data to be allocated off of the heap when you use it to
send or receive data.

> static int smsc95xx_read_reg(struct usbnet *dev, u32 index, u32 *data)

Is data always allocated off of the heap here?

thanks,

greg k-h