On 2011-07-22 19:20, Tanu Kaskinen wrote:
Untested code, don't commit willy-nilly... I'll be away for
the weekend, and I thought I'd already send this patch for
review. I'll test this some day next week.

I've made a quick code review (no real testing). I think most of it looks good.

element_change_off_and_zero_to_constant() is introduced to
make the volume subset checking easier. element_dB_to_step and
element_alsa_dB_to_step help with getting the step for 0 dB
without tons of annoying ifs. They could probably be used also
elsewhere in the code, but I'll do that cleanup later.

As well as cleanup all PA_ALSA_VOLUME_OFF and PA_ALSA_VOLUME_ZERO usages.

Colin, there are also a couple of questions for you in the
comments.

I agree with the comments. Although not removing a redundant path is less bad than removing something that should not be removed, so I'm okay with marking them as FIXME's for the time being.

---
  src/modules/alsa/alsa-mixer.c |  132 ++++++++++++++++++++++++++++++-----------
  1 files changed, 96 insertions(+), 36 deletions(-)

diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c
index f6a2a20..8f1fb4a 100644
--- a/src/modules/alsa/alsa-mixer.c
+++ b/src/modules/alsa/alsa-mixer.c
@@ -1344,6 +1344,82 @@ static int check_required(pa_alsa_element *e, 
snd_mixer_elem_t *me) {
      return 0;
  }

+static int element_alsa_dB_to_step(pa_alsa_element *e, snd_mixer_elem_t *me, 
long *dB, long *step) {
+    int r;
+
+    pa_assert(e);
+    pa_assert(me);
+    pa_assert(dB);
+    pa_assert(step);
+
+    if (e->direction == PA_ALSA_DIRECTION_OUTPUT) {
+        if ((r = snd_mixer_selem_ask_playback_dB_vol(me, *dB, +1, step))>= 0) {
+            *step = (e->volume_limit>= 0) ? PA_MIN(*step, e->volume_limit) : 
*step;

But can't volume_limit can be less than zero and still valid?

+
+            if ((r = snd_mixer_selem_ask_playback_vol_dB(me, *step, dB)<  0)) {
+                pa_log("snd_mixer_selem_ask_playback_vol_dB() failed: %s", 
pa_alsa_strerror(r));
+                return -1;
+            }

Nitpick: could be worth adding a comment about why you need to ask first dB -> vol and then vol -> dB again,

+        } else {
+            pa_log("snd_mixer_selem_ask_playback_dB_vol() failed: %s", 
pa_alsa_strerror(r));
+            return -1;
+        }
+    } else {
+        if ((r = snd_mixer_selem_ask_capture_dB_vol(me, *dB, -1, step))>= 0) {
+            *step = (e->volume_limit>= 0) ? PA_MIN(*step, e->volume_limit) : 
*step;
+
+            if ((r = snd_mixer_selem_ask_capture_vol_dB(me, *step, dB)<  0)) {
+                pa_log("snd_mixer_selem_ask_capture_vol_dB() failed: %s", 
pa_alsa_strerror(r));
+                return -1;
+            }
+        } else {
+            pa_log("snd_mixer_selem_ask_capture_dB_vol() failed: %s", 
pa_alsa_strerror(r));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int element_dB_to_step(pa_alsa_element *e, snd_mixer_elem_t *me, long 
*dB, long *step) {
+    pa_assert(e);
+    pa_assert(me);
+    pa_assert(dB);
+    pa_assert(step);
+
+    if (e->db_fix) {
+        int rounding = (e->direction == PA_ALSA_DIRECTION_OUTPUT) ? +1 : -1;
+
+        *step = decibel_fix_get_step(e->db_fix, dB, rounding);
+        return 0;
+    }
+
+    return element_alsa_dB_to_step(e, me, dB, step);
+}
+
+/* If element's volume_use is OFF or ZERO, it's changed to CONSTANT.
+ * If a problem occurs with alsa while doing this, volume_use will be
+ * changed to IGNORE. */
+static void element_change_off_and_zero_to_constant(pa_alsa_element *e, 
snd_mixer_elem_t *me) {
+    pa_assert(e);
+    pa_assert(me);
+
+    if (e->volume_use == PA_ALSA_VOLUME_OFF) {
+        e->volume_use = PA_ALSA_VOLUME_CONSTANT;
+        e->constant_volume = e->min_volume;
+        return;
+    }
+
+    if (e->volume_use == PA_ALSA_VOLUME_ZERO) {
+        long dB = 0;
+        if (element_dB_to_step(e, me,&dB,&e->constant_volume)<  0) {
+            pa_log("Failed to query element's volume step for 0 dB. Ignoring volume 
for element %s.", e->alsa_name);
+            e->volume_use = PA_ALSA_VOLUME_IGNORE;
+        } else
+            e->volume_use = PA_ALSA_VOLUME_CONSTANT;
+    }
+}
+
  static int element_probe(pa_alsa_element *e, snd_mixer_t *m) {
      snd_mixer_selem_id_t *sid;
      snd_mixer_elem_t *me;
@@ -1627,9 +1703,10 @@ static int element_probe(pa_alsa_element *e, snd_mixer_t 
*m) {
                  }
              }
          }
-
      }

+    element_change_off_and_zero_to_constant(e, me);
+
      if (e->switch_use == PA_ALSA_SWITCH_SELECT) {
          pa_alsa_option *o;

@@ -2922,54 +2999,31 @@ static pa_bool_t element_is_subset(pa_alsa_element *a, 
pa_alsa_element *b, snd_m

      /* Check the volume_use */
      if (a->volume_use != PA_ALSA_VOLUME_IGNORE) {
+        if (b->volume_use == PA_ALSA_VOLUME_IGNORE)
+            return FALSE;
+
+        /* ZERO and OFF should have been changed into CONSTANT
+         * while probing the elements. */
+        pa_assert(a->volume_use == PA_ALSA_VOLUME_MERGE || a->volume_use == 
PA_ALSA_VOLUME_CONSTANT);
+        pa_assert(b->volume_use == PA_ALSA_VOLUME_MERGE || b->volume_use == 
PA_ALSA_VOLUME_CONSTANT);

          /* "Constant" is subset of "Constant" only when their constant values 
are equal */
          if (a->volume_use == PA_ALSA_VOLUME_CONSTANT&&  b->volume_use == 
PA_ALSA_VOLUME_CONSTANT&&  a->constant_volume != b->constant_volume)
              return FALSE;

-        /* Different volume uses when b is not "Merge" means we are definitely 
not a subset */
-        if (a->volume_use != b->volume_use&&  b->volume_use != 
PA_ALSA_VOLUME_MERGE)
+        /* "Merge" is never a subset of "Constant" */
+        if (a->volume_use == PA_ALSA_VOLUME_MERGE&&  b->volume_use == 
PA_ALSA_VOLUME_CONSTANT)
              return FALSE;

          /* "Constant" is a subset of "Merge", if there is not a "volume-limit" in 
"Merge" below the actual constant.
-         * "Zero" and "Off" are just special cases of "Constant" when comparing to 
"Merge"
           * "Merge" with a "volume-limit" is a subset of "Merge" without a 
"volume-limit" or with a higher "volume-limit" */
          if (b->volume_use == PA_ALSA_VOLUME_MERGE&&  b->volume_limit>= 0) {
              long a_limit;

              if (a->volume_use == PA_ALSA_VOLUME_CONSTANT)
                  a_limit = a->constant_volume;
-            else if (a->volume_use == PA_ALSA_VOLUME_ZERO) {
-                long dB = 0;
-
-                if (a->db_fix) {
-                    int rounding = (a->direction == PA_ALSA_DIRECTION_OUTPUT ? 
+1 : -1);
-                    a_limit = decibel_fix_get_step(a->db_fix,&dB, rounding);
-                } else {
-                    snd_mixer_selem_id_t *sid;
-                    snd_mixer_elem_t *me;
-
-                    SELEM_INIT(sid, a->alsa_name);
-                    if (!(me = snd_mixer_find_selem(m, sid))) {
-                        pa_log_warn("Element %s seems to have disappeared.", 
a->alsa_name);
-                        return FALSE;
-                    }
-
-                    if (a->direction == PA_ALSA_DIRECTION_OUTPUT) {
-                        if (snd_mixer_selem_ask_playback_dB_vol(me, dB, 
+1,&a_limit)<  0)
-                            return FALSE;
-                    } else {
-                        if (snd_mixer_selem_ask_capture_dB_vol(me, dB, 
-1,&a_limit)<  0)
-                            return FALSE;
-                    }
-                }
-            } else if (a->volume_use == PA_ALSA_VOLUME_OFF)
-                a_limit = a->min_volume;
-            else if (a->volume_use == PA_ALSA_VOLUME_MERGE)
-                a_limit = a->volume_limit;
              else
-                /* This should never be reached */
-                pa_assert(FALSE);
+                a_limit = a->volume_limit;

              if (a_limit>  b->volume_limit)
                  return FALSE;
@@ -2977,6 +3031,9 @@ static pa_bool_t element_is_subset(pa_alsa_element *a, 
pa_alsa_element *b, snd_m
      }

      if (a->switch_use != PA_ALSA_SWITCH_IGNORE) {
+        if (b->switch_use == PA_ALSA_SWITCH_IGNORE)
+            return FALSE;
+
          /* "On" is a subset of "Mute".
           * "Off" is a subset of "Mute".
           * "On" is a subset of "Select", if there is an "Option:On" in B.
@@ -3022,9 +3079,8 @@ static void path_set_condense(pa_alsa_path_set *ps, 
snd_mixer_t *m) {
      if (!ps->paths || !ps->paths->next)
          return;

-    for (p = ps->paths; p; p = np) {
+    PA_LLIST_FOREACH_SAFE(p, np, ps->paths) {
          pa_alsa_path *p2;
-        np = p->next;

          PA_LLIST_FOREACH(p2, ps->paths) {
              pa_alsa_element *ea, *eb;
@@ -3043,6 +3099,8 @@ static void path_set_condense(pa_alsa_path_set *ps, 
snd_mixer_t *m) {
                          ea = ea->next;
                          eb = eb->next;
                          if ((ea&&  !eb) || (!ea&&  eb))
+                            /* Question to Colin: Do we really want to require 
that p and p2 contain an equal amount of elements to consider p a subset of p2?
+                             * Isn't it enough if p2 contains all elements of 
p? */
                              is_subset = FALSE;
                          else if (!ea&&  !eb)
                              break;
@@ -3050,6 +3108,8 @@ static void path_set_condense(pa_alsa_path_set *ps, 
snd_mixer_t *m) {
                          is_subset = FALSE;

                  } else
+                    /* Question to Colin: Do we really want to require that p 
and p2 contain their elements in the exact same order?
+                     * Is there a guarantee for that? (I haven't inspected the 
code that closely.) */
                      is_subset = FALSE;
              }



--
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic
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