Re: [PATCH i2c-tools v2 2/2] i2ctransfer: Add optional message modifier flags

["Benoît Monin" <benoit.monin@bootlin.com>]

On Tuesday, 13 January 2026 at 18:33:53 CET, Wolfram Sang wrote:
[...]
> >  		"  DATA are LENGTH bytes for a write message. They can be shortened by a suffix:\n"
> >  		"    = (keep value constant until LENGTH)\n"
> >  		"    + (increase value by 1 until LENGTH)\n"
> > @@ -202,12 +209,21 @@ int main(int argc, char *argv[])
> >  		case PARSE_GET_DESC:
> >  			flags = 0;
> >  
> > -			switch (*arg_ptr++) {
> > -			case 'r': flags |= I2C_M_RD; break;
> > -			case 'w': break;
> > -			default:
> > -				fprintf(stderr, "Error: Invalid direction\n");
> > -				goto err_out_with_arg;
> > +			for (int done = 0; !done; ) {
> > +				switch (*arg_ptr++) {
> > +				/* optional flags */
> > +				case 'i': flags |= I2C_M_IGNORE_NAK; break;
> > +				case 'n': flags |= I2C_M_NO_RD_ACK; break;
> > +				case 'p': flags |= I2C_M_STOP; break;
> > +				case 's': flags |= I2C_M_NOSTART; break;
> > +				case 't': flags |= I2C_M_REV_DIR_ADDR; break;
> 
> Brainstorming here: maybe a macro could help:
> 
> 	case 'i': add_flag_if_supported(flags, I2C_M_IGNORE_NAK);
> 
> ?
> 
I am having a hard time coming up with something here. There is the
__is_defined() macro in the kernel source[1], it only returns 0 or 1, not
the value of the define.

Maybe defining as zero the flags that are undefined would be acceptable?
E.g.

#ifndef I2C_M_IGNORE_NAK
#define I2C_M_IGNORE_NAK 0
#endif

Or you have another idea?

[1]: https://elixir.bootlin.com/linux/v6.19-rc5/source/tools/include/linux/kconfig.h#L35

Thanks for the review!
-- 
Benoît