On 2017/12/7 17:03, Arnd Bergmann wrote:
> On Thu, Dec 7, 2017 at 9:16 AM, Xiongfeng Wang
> <wangxiongfe...@huawei.com> wrote:
>> gcc prints the following warning:
>> drivers/auxdisplay/img-ascii-lcd.c: In function ‘malta_update’:
>> drivers/auxdisplay/img-ascii-lcd.c:109: warning: ‘err’ may be usedun
>> initialized in this function
>> drivers/auxdisplay/img-ascii-lcd.c: In function ‘sead3_update’:
>> drivers/auxdisplay/img-ascii-lcd.c:207: warning: ‘err’ may be used
>> uninitialized in this function
>>
>> When ctx->cfg->num_chars is zero, there will be a false error info
>> printed. Fix this by recontruct the code and initializing the variable
>> 'err' to zero.
>>
>> Signed-off-by: Xiongfeng Wang <wangxiongfe...@huawei.com>
>
> I wonder how you ran into this. I'm not seeing that warning on my machine,
> and I thought I had fixed all '-Wmaybe-uninitialized' warnings. Before you
> send it to the maintainer, I'd try to figure out what the difference is
> between
> our setups.
Sorry, I forget the designate the 'ARCH' I used. So it's x86 compiler that
prints these warnings.
ARM64 compiler won't report these kind of warnings.
Since 'num_chars'is guaranteed to be a positive number, this is not a real bug.
Please just ignore this patch.
Thanks,
Xiongfeng Wang
>
> Do you get other -Wmaybe-uninitialized warnings in the same build, or is this
> the only one?
>
>> drivers/auxdisplay/img-ascii-lcd.c | 23 +++++++++++------------
>> 1 file changed, 11 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/auxdisplay/img-ascii-lcd.c
>> b/drivers/auxdisplay/img-ascii-lcd.c
>> index db040b3..15048c1 100644
>> --- a/drivers/auxdisplay/img-ascii-lcd.c
>> +++ b/drivers/auxdisplay/img-ascii-lcd.c
>> @@ -102,12 +102,11 @@ static void malta_update(struct img_ascii_lcd_ctx *ctx)
>> for (i = 0; i < ctx->cfg->num_chars; i++) {
>> err = regmap_write(ctx->regmap,
>> ctx->offset + (i * 8), ctx->curr[i]);
>> - if (err)
>> - break;
>> + if (err) {
>> + pr_err_ratelimited("Failed to update LCD display:
>> %d\n", err);
>> + return;
>> + }
>> }
>> -
>> - if (unlikely(err))
>> - pr_err_ratelimited("Failed to update LCD display: %d\n",
>> err);
>> }
>
> This part looks good.
>
>> static struct img_ascii_lcd_config malta_config = {
>> @@ -180,32 +179,32 @@ static int sead3_wait_lcd_idle(struct
>> img_ascii_lcd_ctx *ctx)
>> static void sead3_update(struct img_ascii_lcd_ctx *ctx)
>> {
>> unsigned int i;
>> - int err;
>> + int err = 0;
>>
>> for (i = 0; i < ctx->cfg->num_chars; i++) {
>> err = sead3_wait_lcd_idle(ctx);
>> if (err)
>> - break;
>> + goto out_err;
>>
>> err = regmap_write(ctx->regmap,
>> ctx->offset + SEAD3_REG_LCD_CTRL,
>> SEAD3_REG_LCD_CTRL_SETDRAM | i);
>> if (err)
>> - break;
>> + goto out_err;
>>
>> err = sead3_wait_lcd_idle(ctx);
>> if (err)
>> - break;
>> + goto out_err;
>>
>> err = regmap_write(ctx->regmap,
>> ctx->offset + SEAD3_REG_LCD_DATA,
>> ctx->curr[i]);
>> if (err)
>> - break;
>> + goto out_err;
>> }
>>
>> - if (unlikely(err))
>> - pr_err_ratelimited("Failed to update LCD display: %d\n",
>> err);
>> +out_err:
>> + pr_err_ratelimited("Failed to update LCD display: %d\n", err);
>> }
>
> I think you forgot a 'return' statement befor ethe label here.
>
> Arnd
>
> .
>
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