Re: [PATCH v4 3/5] usb: gadget: udc: add Renesas RZ/N1 USBF controller support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Dec 22, 2022 at 04:24:38PM +0100, Herve Codina wrote:
> Hi Geert, Greg,
> 
> On Wed, 21 Dec 2022 14:07:53 +0100
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> 
> > On Wed, Dec 21, 2022 at 02:03:43PM +0100, Geert Uytterhoeven wrote:
> > > Hi Hervé,
> > > 
> > > On Tue, Dec 13, 2022 at 2:33 PM Herve Codina <herve.codina@bootlin.com> wrote:  
> > > > Add support for the Renesas USBF controller.
> > > > This controller is an USB2.0 UDC controller available in the
> > > > Renesas r9a06g032 SoC (RZ/N1 family).
> > > >
> > > > Signed-off-by: Herve Codina <herve.codina@bootlin.com>  
> > > 
> > > Thanks for your patch!
> > >   
> > > > --- /dev/null
> > > > +++ b/drivers/usb/gadget/udc/renesas_usbf.c  
> > >   
> > > > +#ifdef DEBUG
> > > > +#define TRACE(_fmt, ...) trace_printk("%s: " _fmt, __func__, ##__VA_ARGS__)
> > > > +#define USBF_TRACE_EP_MASK 0x0ffff /* All the 16 endpoints */
> > > > +#define TRACEEP(_ep, _fmt, ...)                                             \
> > > > +       do {                                                                \
> > > > +               if ((1 << (_ep)->id) & USBF_TRACE_EP_MASK)                  \
> > > > +                       trace_printk("%s: " _fmt, __func__, ##__VA_ARGS__); \
> > > > +       } while (0)
> > > > +#else
> > > > +#define TRACE(_fmt, ...) do { } while (0)
> > > > +#define TRACEEP(_ep, _fmt, ...) do { } while (0)  
> > > 
> > > Please use "no_printk(fmt, ##__VA_ARGS__)" instead of dummy loops,
> > > to avoid bad callers going unnoticed if DEBUG is not defined.  
> > 
> > Even better, do NOT define custom debug/trace macros for a single
> > driver, just use the ones that the rest of the kernel uses instead
> > please.
> > 
> > thanks,
> > 
> > greg k-h
> 
> I would like to keep some granularity in debug messages and
> also keep the function name automatically added.
> I propose 3 kinds of messages:
> - general ones,
> - specific Endpoint0 ones,
> - other Endpoints ones.

All of those can work just fine using dev_dbg() today, no need to make
anything special for the driver.  You can turn those messages on/off
with no need to ever rebuild your driver, which is the key point.

> So before doing any modification in the source code, what do you
> think about:
>     /*
>      * Suggested tracers:
>      * - no_printk:    Disable tracing
>      * - trace_printk: Print to trace buffer
>      */
>     #define usbf_dbg(_fmt, ...) no_printk("%s: " _fmt, __func__, ##__VA_ARGS__)
>     #define usbf_dbg_ep0(_fmt, ...) no_printk("%s: " _fmt, __func__, ##__VA_ARGS__)
>     #define usbf_dbg_epn(_fmt, ...) no_printk("%s: " _fmt, __func__, ##__VA_ARGS__)

Nope, just use dev_dbg() only please.  It provides MUCH more
funcationality and a unified interface with the rest of the kernel.
Please do not attempt to "roll your own" version of debugging macros for
just a single driver.

thanks,

greg k-h