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Date: Tue, 25 Apr 2017 13:17:47 +0300
From: Daniel Baluta <daniel.baluta@...il.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Daniel Baluta <daniel.baluta@....com>, alsa-devel@...a-project.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
patches@...nsource.wolfsonmicro.com, Takashi Iwai <tiwai@...e.com>,
Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Subject: Re: [alsa-devel] [PATCH 1/2] ASoC: codec: wm9860: avoid
maybe-uninitialized warning
On Mon, Apr 24, 2017 at 6:27 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Mon, Apr 24, 2017 at 3:15 PM, Daniel Baluta <daniel.baluta@...il.com> wrote:
>> On Fri, Apr 21, 2017 at 5:46 PM, Arnd Bergmann <arnd@...db.de> wrote:
>>> On Fri, Apr 21, 2017 at 3:07 PM, Daniel Baluta <daniel.baluta@....com> wrote:
>>>> The new PLL configuration code triggers a harmless warning:
>>>>
>>>> sound/soc/codecs/wm8960.c: In function 'wm8960_configure_clocking':
>>>> sound/soc/codecs/wm8960.c:735:3: error: 'best_freq_out' may be used
>>>> uninitialized in this function [-Werror=maybe-uninitialized]
>>>> wm8960_set_pll(codec, freq_in, best_freq_out);
>>>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>> sound/soc/codecs/wm8960.c:699:12: note: 'best_freq_out' was declared
>>>> here
>>>>
>>>> Fixes: 84fdc00d519f ("ASoC: codec: wm9860: Refactor PLL out freq search")
>>>> Fixes: 303e8954af8d ("ASoC: codec: wm8960: Stop when a matching PLL freq is found")
>>>> Suggested-by: Arnd Bergmann <arnd@...db.de>
>>>> Signed-off-by: Daniel Baluta <daniel.baluta@....com>
>>>> ---
>>>> Arnd,
>>>>
>>>> I agree that your code was more both humans and gcc anyhow
>>>> for consistency with wm8960_configure_sysclk function I preferred
>>>> to keep the "if(..) break" statements.
>>>
>>> How about changing both functions the same way then?
>>
>> I've tried but I couldn't find any solution. For clarity here is how
>> the code actually looks like.
>>
>> The git diff is a little bit misleading. Here is how wm8960_configure_pll code
>> looks like:
>>
>> https://pastebin.com/naGdVNQz
>>
>> static
>> int wm8960_configure_pll(struct snd_soc_codec *codec, int freq_in,
>> » » » int *sysclk_idx, int *dac_idx, int *bclk_idx)
>> {
>> » struct wm8960_priv *wm8960 = snd_soc_codec_get_drvdata(codec);
>> » int sysclk, bclk, lrclk, freq_out;
>> » int diff, closest, best_freq_out;
>> » int i, j, k;
>>
>> » bclk = wm8960->bclk;
>> » lrclk = wm8960->lrclk;
>> » closest = freq_in;
>>
>> » best_freq_out = -EINVAL;
>> » *sysclk_idx = *dac_idx = *bclk_idx = -1;
>>
>> » for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
>> » » if (sysclk_divs[i] == -1)
>> » » » continue;
>> » » for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
>> » » » sysclk = lrclk * dac_divs[j];
>> » » » freq_out = sysclk * sysclk_divs[i];
>>
>> » » » for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k) {
>> » » » » if (!is_pll_freq_available(freq_in, freq_out))
>> » » » » » continue;
>>
>> » » » » diff = sysclk - bclk * bclk_divs[k] / 10;
>> » » » » if (diff == 0) {
>> » » » » » *sysclk_idx = i;
>> » » » » » *dac_idx = j;
>> » » » » » *bclk_idx = k;
>> » » » » » best_freq_out = freq_out;
>> » » » » » break;
>> » » » » }
>> » » » » if (diff > 0 && closest > diff) {
>> » » » » » *sysclk_idx = i;
>> » » » » » *dac_idx = j;
>> » » » » » *bclk_idx = k;
>> » » » » » closest = diff;
>> » » » » » best_freq_out = freq_out;
>> » » » » }
>> » » » }
>> » » » if (k != ARRAY_SIZE(bclk_divs))
>> » » » » break;
>> » » }
>> » » if (j != ARRAY_SIZE(dac_divs))
>> » » » break;
>> » }
>>
>> » return best_freq_out;
>> }
>>
>> In my opinion this is a compiler false positive. Any clue on how to rework this
>> would be welcomed :). I couldn't find any decent solution.
>
> Actually I think in this case the compiler is supposed to warn if
> best_freq_out is not initialized, as we would never set it
> in case is_pll_freq_available() returns false for all inputs or
> sysclk_divs[] is -1 for all fields.
> I'd leave the initialization then, and only replace the breaks
> with a goto (not tested):
>
>> » for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
>> » » if (sysclk_divs[i] == -1)
>> » » » continue;
>> » » for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
>> » » » sysclk = lrclk * dac_divs[j];
>> » » » freq_out = sysclk * sysclk_divs[i];
>>
>> » » » for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k) {
>> » » » » if (!is_pll_freq_available(freq_in, freq_out))
>> » » » » » continue;
>>
>> » » » » diff = sysclk - bclk * bclk_divs[k] / 10;
>> » » » » if (diff == 0) {
>> » » » » » *sysclk_idx = i;
>> » » » » » *dac_idx = j;
>> » » » » » *bclk_idx = k;
>> » » » » » best_freq_out = freq_out;
>> » » » » » goto out;
>> » » » » }
>> » » » » if (diff > 0 && closest > diff) {
>> » » » » » *sysclk_idx = i;
>> » » » » » *dac_idx = j;
>> » » » » » *bclk_idx = k;
>> » » » » » closest = diff;
>> » » » » » best_freq_out = freq_out;
>> » » » » }
>> » » » }
>> » » }
>> » }
>>out:
>> » return best_freq_out;
>> }
Sure, this looks reasonable. I will send v2.
Daniel.
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