Question

What does this line of code will do.

pcm->card->number, pcm->device both are int.

char str[16];

sprintf(str, "pcmC%iD%ip", pcm->card->number, pcm->device);

it is taken form android/kernel/sound/core/pcm.c.

Answer 1

As of the description of sprintf() and fprintf(), %i is

The int argument is converted to a signed decimal in the style [-]dddd. The precision
specifies the minimum number of digits to appear; if the value being converted can be
represented in fewer digits, it will be expanded with leading zeros. The default precision
is 1. The result of converting 0 with an explicit precision of 0 is no characters.

So the result is e.g. pcmC12D23p if pcm->card->number == 12 and pcm->device == 23.