kernel/trigger: hw post-samples is "sw post-samples - 1"

The hardware acquires pre-samples + the-sample + post-samples while software uses pre+post (the first "post" is the trigger event. This had no visible effects as hw just acquired one sample more, but maybe we'd have error in pathological cases (e.g, a full-ram acquisition). This commit also makes trivial unrelated changes in the same code snippet. Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

kernel/trigger: hw post-samples is "sw post-samples - 1"
The hardware acquires pre-samples + the-sample + post-samples while software uses pre+post (the first "post" is the trigger event. This had no visible effects as hw just acquired one sample more, but maybe we'd have error in pathological cases (e.g, a full-ram acquisition). This commit also makes trivial unrelated changes in the same code snippet. Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
b6b81e29 · Alessandro Rubini · d2d3cc1d · b6b81e29 · b6b81e29
Commit b6b81e29 authored Jul 01, 2013 by Alessandro Rubini
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fmc-adc-driver.in doc/fmc-adc-driver.in +4 -0

fa-zio-trg.c kernel/fa-zio-trg.c +18 -13

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--- a/doc/fmc-adc-driver.in
+++ b/doc/fmc-adc-driver.in
@@ -722,6 +722,10 @@ This is the list of attributes (excluding kernel-generic and ZIO-generic ones):
        total number of samples acquired corresponds to the sum of the
        two numbers.  For multi-shot acquisition, each shot acquires that
        many sample, but pre + post must be at most 2048.
+        @b{Note:} hardware acquires @i{pre+1+post}, while software
+        always used buffers of @i{pre+post} and documented it to be so.
+        The driver fixes the @t{post-samples} value
+        before writing it to hardware.

 @item sw-trg-enable
 @itemx sw-trg-fire

--- a/kernel/fa-zio-trg.c
+++ b/kernel/fa-zio-trg.c
@@ -33,7 +33,7 @@ struct zfat_instance {

 /* zio trigger attributes */
 static ZIO_ATTR_DEFINE_STD(ZIO_TRG, zfat_std_zattr) = {
-	/* Number of shots */
+	/* Number of shots was called NB (number of buffers), so it remains */
 	ZIO_ATTR(trig, ZIO_ATTR_TRIG_N_SHOTS, ZIO_RW_PERM, ZFAT_SHOTS_NB, 1),
 	ZIO_ATTR(trig, ZIO_ATTR_TRIG_PRE_SAMP, ZIO_RW_PERM, ZFAT_PRE, 0),
 	ZIO_ATTR(trig, ZIO_ATTR_TRIG_POST_SAMP, ZIO_RW_PERM, ZFAT_POST, 0),
@@ -81,23 +81,28 @@ static struct zio_attribute zfat_ext_zattr[] = {
 *
 * set a value to a FMC-ADC trigger register
 */
-static int zfat_conf_set(struct device *dev, struct zio_attribute *zattr,
+static int zfat_conf_set(struct device *zdev, struct zio_attribute *zattr,
 			 uint32_t usr_val)
 {
-	struct fa_dev *fa = get_zfadc(dev);
-	struct zio_ti *ti = to_zio_ti(dev);
-	uint32_t tmp_val = usr_val;
-	int err = 0;
+	struct fa_dev *fa = get_zfadc(zdev);
+	struct device *dev = &fa->fmc->dev;
+	struct zio_ti *ti = to_zio_ti(zdev);
+	uint32_t hw_val = usr_val;
+	int err;
+
+	if (zattr->id == ZFAT_SHOTS_NB && usr_val == 0) {
+		dev_info(dev, "nshots cannot be 0\n");
+		return -EINVAL;
+	}

 	switch (zattr->id) {
+
+	case ZFAT_POST:
+		if (usr_val) hw_val--; /* hw uses pre+1+post */
 	case ZFAT_SHOTS_NB:
-		if (!tmp_val) {
-			dev_err(dev, "nshots cannot be 0\n");
-			return -EINVAL;
-		}
+		/* fall through, for oveflow detection */
 	case ZFAT_PRE:
-	case ZFAT_POST:
-		err = zfat_overflow_detection(ti, zattr->id, tmp_val);
+		err = zfat_overflow_detection(ti, zattr->id, usr_val);
 		if (err)
 			return err;
 		break;
@@ -120,7 +125,7 @@ static int zfat_conf_set(struct device *dev, struct zio_attribute *zattr,
 		break;
 	}

-	return zfa_hardware_write(fa, zattr->id, tmp_val);
+	return zfa_hardware_write(fa, zattr->id, hw_val);
 }