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

[Nicolas Pitre]

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.

> 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.


Nicolas