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i2c_subr.c revision 1.3 
      1 /*	$NetBSD: i2c_subr.c,v 1.3 2025/09/20 21:24:29 thorpej Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2003 Wasabi Systems, Inc.
      5  * All rights reserved.
      6  *
      7  * Written by Jason R. Thorpe for Wasabi Systems, Inc.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. All advertising materials mentioning features or use of this software
     18  *    must display the following acknowledgement:
     19  *      This product includes software developed for the NetBSD Project by
     20  *      Wasabi Systems, Inc.
     21  * 4. The name of Wasabi Systems, Inc. may not be used to endorse
     22  *    or promote products derived from this software without specific prior
     23  *    written permission.
     24  *
     25  * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
     26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     27  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
     29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     35  * POSSIBILITY OF SUCH DAMAGE.
     36  */
     37 
     38 #include <sys/cdefs.h>
     39 __KERNEL_RCSID(0, "$NetBSD: i2c_subr.c,v 1.3 2025/09/20 21:24:29 thorpej Exp $");
     40 
     41 #include <sys/param.h>
     42 #include <sys/device.h>
     43 #include <sys/module.h>
     44 
     45 #include <dev/i2c/i2cvar.h>
     46 
     47 MODULE(MODULE_CLASS_EXEC, i2c_subr, NULL);
     48 
     49 static int
     50 i2c_subr_modcmd(modcmd_t cmd, void *opaque)
     51 {
     52 
     53 	switch (cmd) {
     54 	case MODULE_CMD_INIT:
     55 	case MODULE_CMD_FINI:
     56 		return 0;
     57 	default:
     58 		return ENOTTY;
     59 	}
     60 }
     61 
     62 int
     63 iicbus_print(void *aux, const char *pnp)
     64 {
     65 
     66 	if (pnp != NULL)
     67 		aprint_normal("iic at %s", pnp);
     68 
     69 	return UNCONF;
     70 }
     71 
     72 /*
     73  * iic_acquire_bus_lock --
     74  *
     75  *	Acquire an i2c bus lock.  Used by iic_acquire_bus() and other
     76  *	places that need to acquire an i2c-related lock with the same
     77  *	logic.
     78  */
     79 int
     80 iic_acquire_bus_lock(kmutex_t *lock, int flags)
     81 {
     82 	if (flags & I2C_F_POLL) {
     83 		/*
     84 		 * Polling should only be used in rare and/or
     85 		 * extreme circumstances; most i2c clients should
     86 		 * be allowed to sleep.
     87 		 *
     88 		 * Really, the ONLY user of I2C_F_POLL should be
     89 		 * "when cold", i.e. during early autoconfiguration
     90 		 * when there is only proc0, and we might have to
     91 		 * read SEEPROMs, etc.  There should be no other
     92 		 * users interfering with our access of the i2c bus
     93 		 * in that case.
     94 		 */
     95 		if (mutex_tryenter(lock) == 0) {
     96 			return EBUSY;
     97 		}
     98 	} else {
     99 		/*
    100 		 * N.B. We implement this as a mutex that we hold across
    101 		 * across a series of requests beause we'd like to get the
    102 		 * priority boost if a higher-priority process wants the
    103 		 * i2c bus while we're asleep waiting for the controller
    104 		 * to perform the I/O.
    105 		 *
    106 		 * XXXJRT Disable preemption here?  We'd like to keep the
    107 		 * CPU while holding this resource, unless we release it
    108 		 * voluntarily (which should only happen while waiting for
    109 		 * a controller to complete I/O).
    110 		 */
    111 		mutex_enter(lock);
    112 	}
    113 
    114 	return 0;
    115 }
    116 
    117 /*
    118  * iic_release_bus_lock --
    119  *
    120  *	Release a previously-acquired i2c-related bus lock.
    121  */
    122 void
    123 iic_release_bus_lock(kmutex_t *lock)
    124 {
    125 	mutex_exit(lock);
    126 }
    127