* re: ALSA: line6: Fix volume calculation for big-endian
@ 2015-03-05 10:21 Dan Carpenter
2015-03-05 12:01 ` Takashi Iwai
0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2015-03-05 10:21 UTC (permalink / raw)
To: tiwai; +Cc: alsa-devel, kernel-janitors
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
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: ALSA: line6: Fix volume calculation for big-endian
2015-03-05 10:21 ALSA: line6: Fix volume calculation for big-endian Dan Carpenter
@ 2015-03-05 12:01 ` Takashi Iwai
0 siblings, 0 replies; 2+ messages in thread
From: Takashi Iwai @ 2015-03-05 12:01 UTC (permalink / raw)
To: Dan Carpenter; +Cc: alsa-devel, kernel-janitors
At Thu, 5 Mar 2015 13:21:49 +0300,
Dan Carpenter wrote:
>
> 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. :)
No mystery, just left/right swapped. It's a common mistake, and
you'll feel the same when you go from Paris to London and look at a
street. I'll fix them (the code, not the street).
thanks,
Takashi
^ permalink raw reply [flat|nested] 2+ messages in thread
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