aci.c

讲述linux的初始化过程

/*
 * Audio Command Interface (ACI) driver (sound/aci.c)
 *
 * ACI is a protocol used to communicate with the microcontroller on
 * some sound cards produced by miro, e.g. the miroSOUND PCM12 and
 * PCM20. The ACI has been developed for miro by Norberto Pellicci
 * <[e-mail]>. Special thanks to both him and miro for
 * providing the ACI specification.
 *
 * The main function of the ACI is to control the mixer and to get a
 * product identification. On the PCM20, ACI also controls the radio
 * tuner on this card, this is supported in the Video for Linux 
 * radio-miropcm20 driver.
 * 
 * This Voxware ACI driver currently only supports the ACI functions
 * on the miroSOUND PCM12 and PCM20 card. Support for miro sound cards 
 * with additional ACI functions can easily be added later.
 *
 * / NOTE / When compiling as a module, make sure to load the module 
 * after loading the mad16 module. The initialisation code expects the
 * MAD16 default mixer to be already available.
 *
 * Revision history:
 *
 *   1995-11-10  Markus Kuhn <[e-mail]>
 *        First version written.
 *   1995-12-31  Markus Kuhn
 *        Second revision, general code cleanup.
 *   1996-05-16	 Hannu Savolainen
 *	  Integrated with other parts of the driver.
 *   1996-05-28  Markus Kuhn
 *        Initialize CS4231A mixer, make ACI first mixer,
 *        use new private mixer API for solo mode.
 *   1998-08-18  Ruurd Reitsma <[e-mail]>
 *	  Small modification to export ACI functions and 
 *	  complete modularisation.
 */

/*
 * Some driver specific information and features:
 *
 * This mixer driver identifies itself to applications as "ACI" in
 * mixer_info.id as retrieved by ioctl(fd, SOUND_MIXER_INFO, &mixer_info).
 *
 * Proprietary mixer features that go beyond the standard OSS mixer
 * interface are:
 * 
 * Full duplex solo configuration:
 *
 *   int solo_mode;
 *   ioctl(fd, SOUND_MIXER_PRIVATE1, &solo_mode);
 *
 *   solo_mode = 0: deactivate solo mode (default)
 *   solo_mode > 0: activate solo mode
 *                  With activated solo mode, the PCM input can not any
 *                  longer hear the signals produced by the PCM output.
 *                  Activating solo mode is important in duplex mode in order
 *                  to avoid feedback distortions.
 *   solo_mode < 0: do not change solo mode (just retrieve the status)
 *
 *   When the ioctl() returns 0, solo_mode contains the previous
 *   status (0 = deactivated, 1 = activated). If solo mode is not
 *   implemented on this card, ioctl() returns -1 and sets errno to
 *   EINVAL.
 *
 */

#include <linux/init.h>
#include <linux/module.h> 

#include "sound_config.h"

#undef  DEBUG		/* if defined, produce a verbose report via syslog */

int aci_port = 0x354;	/* as determined by bit 4 in the OPTi 929 MC4 register */
unsigned char aci_idcode[2] = {0, 0};	/* manufacturer and product ID */
unsigned char aci_version = 0;		/* ACI firmware version	*/
int aci_solo;		/* status bit of the card that can't be		*
			 * checked with ACI versions prior to 0xb0	*/

static int aci_present = 0;

#ifdef MODULE                  /* Whether the aci mixer is to be reset.    */
int aci_reset = 0;             /* Default: don't reset if the driver is a  */
MODULE_PARM(aci_reset,"i");
#else                          /* module; use "insmod aci.o aci_reset=1" */
int aci_reset = 1;             /* to override.                             */
#endif


#define COMMAND_REGISTER    (aci_port)
#define STATUS_REGISTER     (aci_port + 1)
#define BUSY_REGISTER       (aci_port + 2)

/*
 * Wait until the ACI microcontroller has set the READYFLAG in the
 * Busy/IRQ Source Register to 0. This is required to avoid
 * overrunning the sound card microcontroller. We do a busy wait here,
 * because the microcontroller is not supposed to signal a busy
 * condition for more than a few clock cycles. In case of a time-out,
 * this function returns -1.
 *
 * This busy wait code normally requires less than 15 loops and
 * practically always less than 100 loops on my i486/DX2 66 MHz.
 *
 * Warning: Waiting on the general status flag after reseting the MUTE
 * function can take a VERY long time, because the PCM12 does some kind
 * of fade-in effect. For this reason, access to the MUTE function has
 * not been implemented at all.
 */

static int busy_wait(void)
{
	long timeout;

	for (timeout = 0; timeout < 10000000L; timeout++)
		if ((inb_p(BUSY_REGISTER) & 1) == 0)
			return 0;

#ifdef DEBUG
	printk("ACI: READYFLAG timed out.\n");
#endif

	return -1;
}


/*
 * Read the GENERAL STATUS register.
 */

static int read_general_status(void)
{
	unsigned long flags;
	int status;

	save_flags(flags);
	cli();
	
	if (busy_wait()) {
		restore_flags(flags);
		return -1;
	}
	
	status = (unsigned) inb_p(STATUS_REGISTER);
	restore_flags(flags);
	return status;
}


/*
 * The four ACI command types (implied, write, read and indexed) can
 * be sent to the microcontroller using the following four functions.
 * If a problem occurred, they return -1.
 */

int aci_implied_cmd(unsigned char opcode)
{
	unsigned long flags;

#ifdef DEBUG
	printk("ACI: aci_implied_cmd(0x%02x)\n", opcode);
#endif

	save_flags(flags);
	cli();
  
  	if (read_general_status() < 0 || busy_wait()) {
		restore_flags(flags);
		return -1;
	}
	
	outb_p(opcode, COMMAND_REGISTER);

	restore_flags(flags);
	return 0;
}


int aci_write_cmd(unsigned char opcode, unsigned char parameter)
{
	unsigned long flags;
	int status;

#ifdef DEBUG
	printk("ACI: aci_write_cmd(0x%02x, 0x%02x)\n", opcode, parameter);
#endif

	save_flags(flags);
	cli();
	
	if (read_general_status() < 0 || busy_wait()) {
		restore_flags(flags);
		return -1;
	}

	outb_p(opcode, COMMAND_REGISTER);
	if (busy_wait()) {
		restore_flags(flags);
		return -1;
	}

	outb_p(parameter, COMMAND_REGISTER);

	if ((status = read_general_status()) < 0) {
		restore_flags(flags);
		return -1;
	}

	/* polarity of the INVALID flag depends on ACI version */
	if ((aci_version <  0xb0 && (status & 0x40) != 0) ||
	  (aci_version >= 0xb0 && (status & 0x40) == 0)) {
	  	restore_flags(flags);
		printk("ACI: invalid write command 0x%02x, 0x%02x.\n",
			opcode, parameter);
		return -1;
	}

	restore_flags(flags);
	return 0;
}

/*
 * This write command send 2 parameters instead of one.
 * Only used in PCM20 radio frequency tuning control
 */

int aci_write_cmd_d(unsigned char opcode, unsigned char parameter, unsigned char parameter2)
{
	unsigned long flags;
	int status;

#ifdef DEBUG
	printk("ACI: aci_write_cmd_d(0x%02x, 0x%02x)\n", opcode, parameter, parameter2);
#endif

	save_flags(flags);
	cli();
	
	if (read_general_status() < 0 || busy_wait()) {
		restore_flags(flags);
		return -1;
	}

	outb_p(opcode, COMMAND_REGISTER);
	if (busy_wait()) {
		restore_flags(flags);
		return -1;
	}

	outb_p(parameter, COMMAND_REGISTER);
	if (busy_wait()) {
		restore_flags(flags);
		return -1;
	}
	
	outb_p(parameter2, COMMAND_REGISTER);
	
	if ((status = read_general_status()) < 0) {
		restore_flags(flags);
		return -1;
	}
	
	/* polarity of the INVALID flag depends on ACI version */
	if ((aci_version <  0xb0 && (status & 0x40) != 0) ||
	  (aci_version >= 0xb0 && (status & 0x40) == 0)) {
		restore_flags(flags);
#if 0	/* Frequency tuning works, but the INVALID flag is set ??? */
		printk("ACI: invalid write (double) command 0x%02x, 0x%02x, 0x%02x.\n",
			opcode, parameter, parameter2);
#endif
		return -1;
  	}
	
	restore_flags(flags);
	return 0;
}

int aci_read_cmd(unsigned char opcode, int length, unsigned char *parameter)
{
	unsigned long flags;
	int i = 0;
	
	save_flags(flags);
	cli();
 
 	if (read_general_status() < 0) {
		restore_flags(flags);
		return -1;
	}
	while (i < length) {
		if (busy_wait()) {
			restore_flags(flags);
			return -1;
		}
			
		outb_p(opcode, COMMAND_REGISTER);
		if (busy_wait()) {
			restore_flags(flags);
			return -1;
		}
			
		parameter[i++] = inb_p(STATUS_REGISTER);
#ifdef DEBUG
		if (i == 1)
			printk("ACI: aci_read_cmd(0x%02x, %d) = 0x%02x\n",
				opcode, length, parameter[i-1]);
		else
			printk("ACI: aci_read_cmd cont.: 0x%02x\n", parameter[i-1]);
#endif
	}

	restore_flags(flags);
	return 0;
}


int aci_indexed_cmd(unsigned char opcode, unsigned char index,
		       unsigned char *parameter)
{
	unsigned long flags;

	save_flags(flags);
	cli();
  
	if (read_general_status() < 0 || busy_wait()) {
	  	restore_flags(flags);
		return -1;
	}
	
	outb_p(opcode, COMMAND_REGISTER);
	if (busy_wait()) {
		restore_flags(flags);
		return -1;
	}
	
	outb_p(index, COMMAND_REGISTER);
	if (busy_wait()) {
		restore_flags(flags);
		return -1;
	}
	
	*parameter = inb_p(STATUS_REGISTER);
#ifdef DEBUG
	printk("ACI: aci_indexed_cmd(0x%02x, 0x%02x) = 0x%02x\n", opcode, index,
		*parameter);
#endif

	restore_flags(flags);
	return 0;
}


/*
 * The following macro SCALE can be used to scale one integer volume
 * value into another one using only integer arithmetic. If the input
 * value x is in the range 0 <= x <= xmax, then the result will be in
 * the range 0 <= SCALE(xmax,ymax,x) <= ymax.
 *
 * This macro has for all xmax, ymax > 0 and all 0 <= x <= xmax the