Merge branch 't/alsa_poll_fd'
authorAndre Noll <maan@systemlinux.org>
Thu, 18 Aug 2011 13:19:41 +0000 (15:19 +0200)
committerAndre Noll <maan@systemlinux.org>
Thu, 18 Aug 2011 13:21:05 +0000 (15:21 +0200)
NEWS
alsa_write.c
error.h

diff --git a/NEWS b/NEWS
index 40c30bf..05c866b 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -20,6 +20,7 @@ are the highlights of this release.
          tarballs. This reduces the size of the tarballs but requires
          gengetopt to build the tarball.
        - Compiles cleanly also with llvm/clang.
+       - The alsa writer used poll fds instead of computing timeouts.
        - Corrupt mp3 files are handled more gracefully.
        - sched: Optimized zero timeouts.
        - vss timeout cleanups.
index 5965159..047e88f 100644 (file)
@@ -52,6 +52,8 @@ struct private_alsa_write_data {
         */
        unsigned channels;
        struct timeval drain_barrier;
+       /* File descriptor for select(). */
+       int poll_fd;
 };
 
 static snd_pcm_format_t get_alsa_pcm_format(enum sample_format sf)
@@ -143,11 +145,13 @@ static int alsa_init(struct private_alsa_write_data *pad,
 
 static void alsa_write_pre_select(struct sched *s, struct task *t)
 {
+       struct pollfd pfd;
        struct writer_node *wn = container_of(t, struct writer_node, task);
        struct private_alsa_write_data *pad = wn->private_data;
-       snd_pcm_sframes_t avail, underrun;
        int ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
 
+       if (pad)
+               pad->poll_fd = -1;
        if (ret == 0)
                return;
        if (!pad) {
@@ -158,25 +162,14 @@ static void alsa_write_pre_select(struct sched *s, struct task *t)
                sched_request_barrier_or_min_delay(&pad->drain_barrier, s);
                return;
        }
-       /*
-        * Data is available to be written to the alsa handle.  Compute number
-        * of milliseconds until next buffer underrun would occur.
-        *
-        * snd_pcm_avail_update() updates the current available count of
-        * samples for writing.  It is a light method to obtain current stream
-        * position, because it does not require the user <-> kernel context
-        * switch, but the value is less accurate, because ring buffer pointers
-        * are updated in kernel drivers only when an interrupt occurs.
-        */
-       avail = snd_pcm_avail_update(pad->handle);
-       if (avail < 0)
-               avail = 0;
-       underrun = (pad->buffer_frames - avail) * pad->buffer_time
-               / pad->buffer_frames / 1000;
-       if (underrun < 50)
-               underrun = 50;
-       underrun -= 50;
-       sched_request_timeout_ms(underrun, s);
+       ret = snd_pcm_poll_descriptors(pad->handle, &pfd, 1);
+       if (ret < 0) {
+               PARA_ERROR_LOG("%s\n", snd_strerror(-ret));
+               t->error = -E_ALSA_POLL_FDS;
+               return;
+       }
+       pad->poll_fd = pfd.fd;
+       para_fd_set(pfd.fd, &s->rfds, &s->max_fileno);
 }
 
 static void alsa_close(struct writer_node *wn)
@@ -255,6 +248,8 @@ again:
                wn->min_iqs = pad->bytes_per_frame;
                goto again;
        }
+       if (pad->poll_fd >= 0 && !FD_ISSET(pad->poll_fd, &s->rfds))
+               return;
        frames = bytes / pad->bytes_per_frame;
        frames = snd_pcm_writei(pad->handle, data, frames);
        if (frames == 0 || frames == -EAGAIN)
diff --git a/error.h b/error.h
index b807877..da0efc4 100644 (file)
--- a/error.h
+++ b/error.h
@@ -441,6 +441,7 @@ extern const char **para_errlist[];
        PARA_ERROR(SET_RATE, "snd_pcm_hw_params_set_rate_near failed"), \
        PARA_ERROR(START_THRESHOLD, "snd_pcm_sw_params_set_start_threshold() failed"), \
        PARA_ERROR(STOP_THRESHOLD, "snd_pcm_sw_params_set_stop_threshold() failed"), \
+       PARA_ERROR(ALSA_POLL_FDS, "could not get alsa poll fd"), \
 
 
 #define WRITE_COMMON_ERRORS \