baylibre-acme: Optimize reading of values from sysfs.

[libsigrok.git] / src / hardware / baylibre-acme / protocol.c

diff --git a/src/hardware/baylibre-acme/protocol.c b/src/hardware/baylibre-acme/protocol.c
index f8fdb595435a21a49dc18fa6dcb03fcc9e16b331..dfd634bb380ee60a121b9b6f5205a5068b7f1fb4 100644 (file)
--- a/src/hardware/baylibre-acme/protocol.c
+++ b/src/hardware/baylibre-acme/protocol.c
@@ -33,6 +33,7 @@ struct channel_group_priv {
 
 struct channel_priv {
        int ch_type;
+       int fd;
        struct channel_group_priv *probe;
 };
 
@@ -494,10 +495,32 @@ static float adjust_data(int val, int type)
 static float read_sample(struct sr_channel *ch)
 {
        struct channel_priv *chp;
-       char path[64], *file, buf[16];
+       char buf[16];
        ssize_t len;
        int fd;
 
+       chp = ch->priv;
+       fd = chp->fd;
+
+       lseek(fd, 0, SEEK_SET);
+
+       len = read(fd, buf, sizeof(buf));
+       if (len < 0) {
+               sr_err("Error reading from channel %s (hwmon: %s): %s",
+                       ch->name, chp->probe->hwmon_num, strerror(errno));
+               ch->enabled = FALSE;
+               return -1.0;
+       }
+
+       return adjust_data(strtol(buf, NULL, 10), chp->ch_type);
+}
+
+SR_PRIV int bl_acme_open_channel(struct sr_channel *ch)
+{
+       struct channel_priv *chp;
+       char path[64], *file;
+       int fd;
+
        chp = ch->priv;
 
        switch (chp->ch_type) {
@@ -508,27 +531,31 @@ static float read_sample(struct sr_channel *ch)
        case TEMP_OUT:  file = "temp2_input";   break;
        default:
                sr_err("Invalid channel type: %d.", chp->ch_type);
-               return -1.0;
+               return SR_ERR;
        }
 
        snprintf(path, sizeof(path), "/sys/class/hwmon/hwmon%d/%s",
                 chp->probe->hwmon_num, file);
+
        fd = open(path, O_RDONLY);
        if (fd < 0) {
                sr_err("Error opening %s: %s", path, strerror(errno));
                ch->enabled = FALSE;
-               return -1.0;
+               return SR_ERR;
        }
 
-       len = read(fd, buf, sizeof(buf));
-       close(fd);
-       if (len < 0) {
-               sr_err("Error reading from %s: %s", path, strerror(errno));
-               ch->enabled = FALSE;
-               return -1.0;
-       }
+       chp->fd = fd;
 
-       return adjust_data(strtol(buf, NULL, 10), chp->ch_type);
+       return 0;
+}
+
+SR_PRIV void bl_acme_close_channel(struct sr_channel *ch)
+{
+       struct channel_priv *chp;
+
+       chp = ch->priv;
+       close(chp->fd);
+       chp->fd = -1;
 }
 
 SR_PRIV int bl_acme_receive_data(int fd, int revents, void *cb_data)