Hello Takashi Iwai,
The patch 0416980d0a2b: "ALSA: line6: Fix volume calculation for
big-endian" from Jan 28, 2015, leads to the following static checker
warning:
sound/usb/line6/playback.c:42 change_volume()
warn: always clamps to s16min
sound/usb/line6/playback.c:57 change_volume()
warn: always clamps to (-8388608)
sound/usb/line6/playback.c:129 add_monitor_signal()
warn: always clamps to s16min
sound/usb/line6/playback.c
25 static void change_volume(struct urb *urb_out, int volume[],
26 int bytes_per_frame)
27 {
28 int chn = 0;
29
30 if (volume[0] == 256 && volume[1] == 256)
31 return; /* maximum volume - no change */
32
33 if (bytes_per_frame == 4) {
34 __le16 *p, *buf_end;
35
36 p = (__le16 *)urb_out->transfer_buffer;
37 buf_end = p + urb_out->transfer_buffer_length / sizeof(*p);
38
39 for (; p < buf_end; ++p) {
40 short pv = le16_to_cpu(*p);
41 int val = (pv * volume[chn & 1]) >> 8;
42 pv = clamp(val, 0x7fff, -0x8000);
^^^^^^^^^^^^^^^^
You didn't really add this, but you might know what was intended here.
It is a complete mystery to me. :)
43 *p = cpu_to_le16(pv);
44 ++chn;
45 }
46 } else if (bytes_per_frame == 6) {
47 unsigned char *p, *buf_end;
48
49 p = (unsigned char *)urb_out->transfer_buffer;
50 buf_end = p + urb_out->transfer_buffer_length;
51
52 for (; p < buf_end; p += 3) {
53 int val;
54
55 val = p[0] + (p[1] << 8) + ((signed char)p[2] << 16);
56 val = (val * volume[chn & 1]) >> 8;
57 val = clamp(val, 0x7fffff, -0x800000);
^^^^^^^^^^^^^^^^^^^^
58 p[0] = val;
59 p[1] = val >> 8;
60 p[2] = val >> 16;
61 ++chn;
62 }
63 }
64 }
[snip]
127 short piv = le16_to_cpu(*pi);
128 int val = pov + ((piv * volume) >> 8);
129 pov = clamp(val, 0x7fff, -0x8000);
^^^^^^^^^^^^^^^^
130 *po = cpu_to_le16(pov);
131 }
regards,
dan carpenter
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