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@sakamocchi.jp
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