Re: [Hdaps-devel] Re: [ltp] IBM HDAPS Someone interested? (Accelerometer)

[Dave Hansen <dave@sr71.net>]

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On Sun, 2005-07-03 at 20:17 +0200, Jesper Juhl wrote:
>         while (1) {
....
>                 } else if (time_before(jiffies, wait_until)) {
>                         set_current_state(TASK_INTERRUPTIBLE);
>                         schedule_timeout(HZ);
>                 } else {

Please don't do the manual task state setting.  It's preferable to just
use msleep_interruptable().  jiffies and HZ can change with each kernel
configuration, and are not dependable.  

I've attached an untested patch that cleans up the init function a bit
(I think).

-- Dave

[-- Attachment #2: init-function-cleanup.patch --]
[-- Type: text/x-patch, Size: 2042 bytes --]

--- accelerometer.c-0.1.orig	2005-07-03 12:28:28.000000000 -0700
+++ accelerometer.c	2005-07-03 12:33:39.000000000 -0700
@@ -158,45 +158,49 @@
 }
 
 /* initialize the accelerometer, wait up to `timeout' seconds for success */
-int accelerometer_init(unsigned int timeout)
+int accelerometer_init(unsigned int timeout_secs)
 {
-	unsigned long wait_until = jiffies + timeout * HZ;
+	unsigned long total_wait_msecs = timeout_secs * 1000;
+	unsinged msec_per_wait = 10;
+	unsigned long msecs_waited = 0;
+	int ret = -EIO;
 	
 	outb(0x13, 0x1610);
 	outb(0x01, 0x161f);
  	if (!wait_latch(0x00, 0x161f))
-		return -EIO;
+		return ret;
 	if (!wait_latch(0x03, 0x1611))
-		return -EIO;
+		return ret;
 	outb(0x17, 0x1610);
 	outb(0x81, 0x1611);
 	outb(0x01, 0x161f);
 	if (!wait_latch(0x00, 0x161f))
-		return -EIO;
+		return ret;
 	if (!wait_latch(0x00, 0x1611))
-		return -EIO;
+		return ret;
 	if (!wait_latch(0x60, 0x1612))
-		return -EIO;
+		return ret;
 	if (!wait_latch(0x00, 0x1613))
-		return -EIO;
+		return ret;
 	outb(0x14, 0x1610);
 	outb(0x01, 0x1611);
 	outb(0x01, 0x161f);
 	if (!wait_latch(0x00, 0x161f))
-		return -EIO;
+		return ret;
 	outb(0x10, 0x1610);
 	outb(0xc8, 0x1611);
 	outb(0x00, 0x1612);
 	outb(0x02, 0x1613);
 	outb(0x01, 0x161f);
 	if (!wait_latch(0x00, 0x161f))
-		return -EIO;
+		return ret;
 	if (!request_refresh(REFRESH_SYNC))
-		return -EIO;
+		return ret;
 	if (!wait_latch(0x00, 0x1611))
-		return -EIO;
+		return ret;
 
-	while (1) {
+	ret = -ENXIO;
+	while (msecs_waited <= total_wait_msecs) {
 		if (wait_latch(0x02, 0x1611)) {
 			struct hdaps_accel_data data;
 			/* 
@@ -204,15 +208,13 @@
 			 * return success.
 			 */
 			 accelerometer_read(&data);
-			return 0;
-		} else if (time_before(jiffies, wait_until)) {
-			set_current_state(TASK_INTERRUPTIBLE);
-			schedule_timeout(HZ);
-		} else {
-			/* we timed out, return failure */
-			return -ENXIO;
+			ret = 0;
+			break;
 		}
+		msleep(msecs_per_wait);
+		msecs_waited += msecs_per_wait;
 	}
+	return ret;
 }
 
 static int ibm_hdaps_init(void)