Hi,
On May 1 2018 15:54, Takashi Iwai wrote:
On Tue, 01 May 2018 05:02:09 +0200,
Takashi Sakamoto wrote:
Hi,
On May 1 2018 00:10, Takashi Iwai wrote:
On Sun, 29 Apr 2018 08:50:23 +0200,
Takashi Sakamoto wrote:
In former commits, proxy structure get members for cache of stream
formats. This commit fills the cache with stream formats at current mode
of sampling transmission frequency.
Signed-off-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>
---
sound/firewire/dice/dice-stream.c | 76 +++++++++++++++++++++++++++++++++++++++
sound/firewire/dice/dice.c | 4 +++
sound/firewire/dice/dice.h | 3 ++
3 files changed, 83 insertions(+)
diff --git a/sound/firewire/dice/dice-stream.c b/sound/firewire/dice/dice-stream.c
index 928a255bfc35..2a9f0cd994a5 100644
--- a/sound/firewire/dice/dice-stream.c
+++ b/sound/firewire/dice/dice-stream.c
@@ -30,6 +30,24 @@ const unsigned int snd_dice_rates[SND_DICE_RATES_COUNT] = {
[6] = 192000,
};
+int snd_dice_stream_get_rate_mode(struct snd_dice *dice,
unsigned int rate,
+ unsigned int *mode)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(snd_dice_rates); i++) {
+ if (!(dice->clock_caps & BIT(i)))
+ continue;
+ if (snd_dice_rates[i] != rate)
+ continue;
+
+ *mode = (i - 1) / 2;
What if i=0? It'll be a negative value?
Yes. But division by 2 to -1 results in 0 because in C language
specification 'truncate toward zero'[1] is applied to discard
fractional part. Then, the result is assigned to value of 'unsigned int'
type. As a result:
0: 32000/44100/48000
1: 88200/96000
2: 176400/192000
This is what I expect.
[1] footnote for '6.5.5 Multiplicative operators' clause in ISO/IEC 9899.
This is too tricky. The result would change dramatically when i were
declared as unsigned.
And I can think of someone trying to change it unsigned because of the
comparison against ARRAY_SIZE() (we've got gcc warnings for that in
the past).
Please make either it more robust or put a proper comment.
Hm. Any comment includes ambiguity, so I prefer the robust
representation with more consumption of .rodata section.
```
int snd_dice_stream_get_rate_mode(struct snd_dice *dice, unsigned int rate,
enum snd_dice_rate_mode *mode)
{
/* Corresponding to each entry in snd_dice_rates. */
static const enum snd_dice_rate_mode modes[] = {
[0] = SND_DICE_RATE_MODE_LOW,
[1] = SND_DICE_RATE_MODE_LOW,
[2] = SND_DICE_RATE_MODE_LOW,
[3] = SND_DICE_RATE_MODE_MIDDLE,
[4] = SND_DICE_RATE_MODE_MIDDLE,
[5] = SND_DICE_RATE_MODE_HIGH,
[6] = SND_DICE_RATE_MODE_HIGH,
};
int i;
for (i = 0; i < ARRAY_SIZE(snd_dice_rates); i++) {
if (!(dice->clock_caps & BIT(i)))
continue;
if (snd_dice_rates[i] != rate)
continue;
*mode = modes[i];
return 0;
}
return -EINVAL;
}
```
Thanks
Takashi Sakamoto
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