Re: new alsa driver for ti omap chip

[Takashi Iwai <tiwai@suse.de>]

At Thu, 12 Feb 2004 12:22:31 +0100 (CET),
Jaroslav wrote:
> 
> On Thu, 12 Feb 2004, Takashi Iwai wrote:
> 
> > At Thu, 12 Feb 2004 12:56:04 +0530,
> > Gupta, Kshitij wrote:
> > > 
> > > hi,
> > > 
> > > 	I am trying to write an alsa driver for a tsc2101 codec on a arm
> > > based SOC.  The control interface between the SOC and the tsc2101 codec is
> > > via SPI. 
> > > And the data interface is a I2S interface.  Can some one suggest a good
> > > starting point to start such a driver.  
> > 
> > some ALSA drivers use their own i2c functions, although there is a
> > generic i2c layer on linux kernel.  for example, delta.c or ews.c of
> > ice1712 driver use i2c (SPI) transfer (which calls ak4xxx-adda.c).
> > but it's rather complex to refer...
> > 
> > the i2c transfer is really easy to implement.  do just like the spec
> > says.  a pseudo code is like below.
> > 
> > 	chip_select_low();
> > 	udelay(1);
> > 
> > 	for (i = 15; i >= 0; i--) {
> > 		set_bit_clock(0);
> > 		udelay(1);
> > 		if (value_to_send & (1 << i))
> > 			set_bit_data(1);
> > 		else
> > 			set_bit_data(0);
> > 		udelay(1);
> > 		set_bit_clock(0);
> > 		udelay(1);
> > 	}
> > 
> > 	chip_select_high();
> 
> Note that I2S is not I2C. I2S is used to connect A/D and D/A converters 
> (three wires - clock, l/r word and sample bit). We don't talk directly 
> with any device over this serial bus.
> 
> I think that the driver must be written for a sound bridge between host
> and the converters. In case of ARM platform, it's usually an integrated
> serial controller which can do DMA transfers.
> 
> So, this I2S question is a bit irrelevant (it's for hardware designers, 
> but not for driver developers).

oh yes, it has nothing to do with I2S, of course.  sorry for
confusion.

but, about the SPI mode to control the chip (not DMA transfer), you
can still check the files above.


Takashi


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