Re: [PATCHv3 1/4] usb: Provide usb_device_speed_name() function

[Michal Nazarewicz]

On Sat, 20 Aug 2011 01:15:00 +0200, Felipe Balbi <balbi@xxxxxx> wrote:

> On Sat, Aug 20, 2011 at 12:32:59AM +0200, Michal Nazarewicz wrote:
> > From: Michal Nazarewicz <mina86@xxxxxxxxxx>
> >
> > In a few places kernel wants to print a human-readable USB
> > device speed name (eg. "high") instead of a raw number
> > (eg. 3).  Usually a switch is introduced in those places
> > leading to code repetition.  To mitigate this issue, this
> > commit introduces usb_device_speed_name() function, which
> > returns a human-readable name of provided speed.
> >
> > Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> > ---
> >  drivers/usb/Makefile          |    3 +++
> >  drivers/usb/common.c          |   24 ++++++++++++++++++++++++
> >  drivers/usb/gadget/udc-core.c |   19 ++-----------------
> >  include/linux/usb/ch9.h       |    8 ++++++++
> >  4 files changed, 37 insertions(+), 17 deletions(-)
> >  create mode 100644 drivers/usb/common.c
> >
> > diff --git a/drivers/usb/Makefile b/drivers/usb/Makefile
> > index 30ddf8d..a3167cc 100644
> > --- a/drivers/usb/Makefile
> > +++ b/drivers/usb/Makefile
> > @@ -51,3 +51,6 @@ obj-$(CONFIG_USB_MUSB_HDRC)	+= musb/
> >  obj-$(CONFIG_USB_RENESAS_USBHS)	+= renesas_usbhs/
> >  obj-$(CONFIG_USB_OTG_UTILS)	+= otg/
> >  obj-$(CONFIG_USB_GADGET)	+= gadget/
> > +
> > +obj-$(CONFIG_USB)		+= common.o
> > +obj-$(CONFIG_USB_GADGET)	+= common.o
> > diff --git a/drivers/usb/common.c b/drivers/usb/common.c
> > new file mode 100644
> > index 0000000..e9d7141
> > --- /dev/null
> > +++ b/drivers/usb/common.c
> > @@ -0,0 +1,24 @@
> > +/*
> > + * Provides code common for host and device side USB.
> > + */
> > +
> > +#include <linux/kernel.h>  /* for ARRAY_SIZE() */
> > +#include <linux/module.h>  /* for EXPORT_SYMBOL_GPL() */
> > +#include <linux/usb/ch9.h>
> > +
> > +const char *usb_device_speed_name(enum usb_device_speed speed)
>
> somehow usb_speed_string() sounds better to me.

Done.

> > +{
> > +	static const char *const names[] = {
> > +		"UNKNOWN",
> > +		"low-speed",
> > +		"full-speed",
> > +		"high-speed",
> > +		"wireless",
> > +		"super-speed",
> > +	};
> > +
> > +	if (speed < 0 || speed >= ARRAY_SIZE(names))
> > +		speed = USB_SPEED_UNKNOWN;
>
> I generally dislike depending on a particular ordering of enumerations.
> While's it's highly unlikely that anyone will change that, if someone
> does change, then it'll take a long time to actually find the bug on the
> print here :-)
>
> I woud rather use a switch in this case.

Would a C99 initialisation be fine by you?

I, myself, have this aversion to switch as being slower (which is
disputable) and too verbose.


> > diff --git a/drivers/usb/gadget/udc-core.c  
> > b/drivers/usb/gadget/udc-core.c
> > index 05ba472..e1ecdbc 100644
> > --- a/drivers/usb/gadget/udc-core.c
> > +++ b/drivers/usb/gadget/udc-core.c
> > @@ -375,23 +375,8 @@ static ssize_t usb_udc_speed_show(struct device  
> > *dev,
> >  		struct device_attribute *attr, char *buf)
> >  {
> >  	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);
> > -	struct usb_gadget	*gadget = udc->gadget;
> > -
> > -	switch (gadget->speed) {
> > -	case USB_SPEED_LOW:
> > -		return snprintf(buf, PAGE_SIZE, "low-speed\n");
> > -	case USB_SPEED_FULL:
> > -		return snprintf(buf, PAGE_SIZE, "full-speed\n");
> > -	case USB_SPEED_HIGH:
> > -		return snprintf(buf, PAGE_SIZE, "high-speed\n");
> > -	case USB_SPEED_WIRELESS:
> > -		return snprintf(buf, PAGE_SIZE, "wireless\n");
> > -	case USB_SPEED_SUPER:
> > -		return snprintf(buf, PAGE_SIZE, "super-speed\n");
> > -	case USB_SPEED_UNKNOWN:	/* FALLTHROUGH */
> > -	default:
> > -		return snprintf(buf, PAGE_SIZE, "UNKNOWN\n");
> > -	}
> > +	return snprintf(buf, PAGE_SIZE, "%s\n",
> > +			usb_device_speed_name(udc->gadget->speed));
> >  }
> >  static DEVICE_ATTR(speed, S_IRUSR, usb_udc_speed_show, NULL);
>
> you said 'several locations', but there's only one ? No other driver is
> using something similar ?

OK, you caught me on being lazy... ;)  Hunted down a few more instances.

--
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michal "mina86" Nazarewicz    (o o)
ooo +-----<email/xmpp: mnazarewicz@xxxxxxxxxx>-----ooO--(_)--Ooo--
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