ALSA: usb - Use strlcat() correctly

Don't pass the advanced position to strlcat() but just gives the buffer
head position so that the max size limit can be checked correctly.
Introduced a new helper function to standaralize strlcat() calls.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/usbmixer.c b/sound/usb/usbmixer.c
index ab5a3ac..9efcfd0 100644 (file)
--- a/sound/usb/usbmixer.c
+++ b/sound/usb/usbmixer.c
@@ -898,6 +898,11 @@ static struct snd_kcontrol_new usb_feature_unit_ctl = {
  * build a feature control
  */
 
+static size_t append_ctl_name(struct snd_kcontrol *kctl, const char *str)
+{
+       return strlcat(kctl->id.name, str, sizeof(kctl->id.name));
+}
+
 static void build_feature_ctl(struct mixer_build *state, unsigned char *desc,
                              unsigned int ctl_mask, int control,
                              struct usb_audio_term *iterm, int unitid)
@@ -978,13 +983,13 @@ static void build_feature_ctl(struct mixer_build *state, unsigned char *desc,
                 */
                if (! mapped_name && ! (state->oterm.type >> 16)) {
                        if ((state->oterm.type & 0xff00) == 0x0100) {
-                               len = strlcat(kctl->id.name, " Capture", sizeof(kctl->id.name));
+                               len = append_ctl_name(kctl, " Capture");
                        } else {
-                               len = strlcat(kctl->id.name + len, " Playback", sizeof(kctl->id.name));
+                               len = append_ctl_name(kctl, " Playback");
                        }
                }
-               strlcat(kctl->id.name + len, control == USB_FEATURE_MUTE ? " Switch" : " Volume",
-                       sizeof(kctl->id.name));
+               append_ctl_name(kctl, control == USB_FEATURE_MUTE ?
+                               " Switch" : " Volume");
                if (control == USB_FEATURE_VOLUME) {
                        kctl->tlv.c = mixer_vol_tlv;
                        kctl->vd[0].access |= 
@@ -1143,7 +1148,7 @@ static void build_mixer_unit_ctl(struct mixer_build *state, unsigned char *desc,
                len = get_term_name(state, iterm, kctl->id.name, sizeof(kctl->id.name), 0);
        if (! len)
                len = sprintf(kctl->id.name, "Mixer Source %d", in_ch + 1);
-       strlcat(kctl->id.name + len, " Volume", sizeof(kctl->id.name));
+       append_ctl_name(kctl, " Volume");
 
        snd_printdd(KERN_INFO "[%d] MU [%s] ch = %d, val = %d/%d\n",
                    cval->id, kctl->id.name, cval->channels, cval->min, cval->max);
@@ -1400,8 +1405,8 @@ static int build_audio_procunit(struct mixer_build *state, int unitid, unsigned
                        if (! len)
                                strlcpy(kctl->id.name, name, sizeof(kctl->id.name));
                }
-               strlcat(kctl->id.name, " ", sizeof(kctl->id.name));
-               strlcat(kctl->id.name, valinfo->suffix, sizeof(kctl->id.name));
+               append_ctl_name(kctl, " ");
+               append_ctl_name(kctl, valinfo->suffix);
 
                snd_printdd(KERN_INFO "[%d] PU [%s] ch = %d, val = %d/%d\n",
                            cval->id, kctl->id.name, cval->channels, cval->min, cval->max);
@@ -1610,9 +1615,9 @@ static int parse_audio_selector_unit(struct mixer_build *state, int unitid, unsi
                        strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
 
                if ((state->oterm.type & 0xff00) == 0x0100)
-                       strlcat(kctl->id.name, " Capture Source", sizeof(kctl->id.name));
+                       append_ctl_name(kctl, " Capture Source");
                else
-                       strlcat(kctl->id.name, " Playback Source", sizeof(kctl->id.name));
+                       append_ctl_name(kctl, " Playback Source");
        }
 
        snd_printdd(KERN_INFO "[%d] SU [%s] items = %d\n",