[PATCH] serial: DCC(JTAG) serial and console emulation support

[Daniel Walker]

On Wed, 2010-10-06 at 10:22 -0400, Nicolas Pitre wrote:
> On Wed, 6 Oct 2010, Daniel Walker wrote:
> 
> > On Tue, 2010-10-05 at 22:55 -0400, Nicolas Pitre wrote:
> > > On Tue, 5 Oct 2010, Daniel Walker wrote:
> > > 
> > > > +#if !defined(CONFIG_CPU_V7)
> > > > +static inline char
> > > > +__dcc_getchar(void)
> > > > +{
> > > > +	char __c;
> > > > +
> > > > +	asm("mrc p14, 0, %0, c0, c5, 0	@ read comms data reg"
> > > > +		: "=r" (__c) : : "cc");
> > > > +
> > > > +	return __c;
> > > > +}
> > > > +#else
> > > > +static inline char
> > > > +__dcc_getchar(void)
> > > > +{
> > > > +	char __c;
> > > > +
> > > > +	asm(
> > > > +	"get_wait:	mrc p14, 0, pc, c0, c1, 0                   \n\
> > > > +			bne get_wait                                    \n\
> > > > +			mrc p14, 0, %0, c0, c5, 0	@ read comms data reg"
> > > > +		: "=r" (__c) : : "cc");
> > > > +
> > > > +	return __c;
> > > > +}
> > > > +#endif
> > > > +
> > > > +#if !defined(CONFIG_CPU_V7)
> > > > +static inline void
> > > > +__dcc_putchar(char c)
> > > > +{
> > > > +	asm("mcr p14, 0, %0, c0, c5, 0	@ write a char"
> > > > +		: /* no output register */
> > > > +		: "r" (c) : "cc");
> > > > +}
> > > > +#else
> > > > +static inline void
> > > > +__dcc_putchar(char c)
> > > > +{
> > > > +	asm(
> > > > +	"put_wait:	mrc p14, 0, pc, c0, c1, 0                   \n\
> > > > +			bcs put_wait                                \n\
> > > > +			mcr p14, 0, %0, c0, c5, 0                   "
> > > > +	: : "r" (c) : "cc");
> > > > +}
> > > > +#endif
> > > 
> > > Please move the #ifdef conditionals inside the respective functions so 
> > > to have only one function pair with the various alternatives embedded 
> > > into them.
> > 
> > My typical clean up policy is do to the inverse of what your suggesting.
> > Mainly because that's the method that I see used extensive in generic
> > parts of the kernel.
> 
> Do you have an example?  I don't see such thing in generic code, unless 
> two versions of the same function are totally different.  In this case 
> you have only the inner inline asm code that is different.

These may not be the best examples but in include/linux/workqueue.h line
150, work_static() for instance if fully inside an ifdef. There is one
other function example in that file, an one macro version. Also some in
include/linux/ftrace.h , but in that case either the functions do
something or nothing. ftrace.h is a little bit confsued, it has example
of it your way and my way.

It doesn't appear to be a constant .. I see it your way and my way.

> > From my perspective there are pluses an minuses to both. Your method
> > reduces lines, and duplication. My method makes the code easier to read.
> 
> I disagree.  In reviewing your patch I had to go back and forth between 
> the different versions just to figure out what was actually different to 
> justify this #ifdef in the first place.  If the #ifdef..#endif was 
> surrounding only the different inline asm statements then the difference 
> would have been more obvious.

You would have had to go back and forth either way , wouldn't you? In
this case the functions are actually totally different.

Daniel

-- 
Sent by an consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum.