linux-kernel - Re: media: i2c: add OV02A10 image sensor driver

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Message-ID: <1607049966.4733.189.camel@mhfsdcap03>
Date:   Fri, 4 Dec 2020 10:46:06 +0800
From:   Dongchun Zhu <dongchun.zhu@...iatek.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Colin Ian King <colin.king@...onical.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-media <linux-media@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        <tfiga@...gle.com>, <sj.huang@...iatek.com>,
        <dongchun.zhu@...iatek.com>
Subject: Re: media: i2c: add OV02A10 image sensor driver

Hi Andy,

On Thu, 2020-12-03 at 20:10 +0200, Andy Shevchenko wrote:
> On Thu, Dec 3, 2020 at 8:03 PM Colin Ian King <colin.king@...onical.com> wrote:
> 
> > Static analysis on linux-next with Coverity has detected an issue with
> > the following commit:
> 
> If you want to fix it properly, see my comments below...
> 
> > 529 static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
> > 530 {
> > 531        struct ov02a10 *ov02a10 = to_ov02a10(sd);
> > 532        struct i2c_client *client =
> > v4l2_get_subdevdata(&ov02a10->subdev);
> >
> >    1. var_decl: Declaring variable ret without initializer.
> >
> > 533        int ret;
> > 534
> > 535        mutex_lock(&ov02a10->mutex);
> > 536
> >
> >    2. Condition ov02a10->streaming == on, taking true branch.
> >
> > 537        if (ov02a10->streaming == on)
> >
> >    3. Jumping to label unlock_and_return.
> >
> > 538                goto unlock_and_return;
> > 539
> > 540        if (on) {
> > 541                ret = pm_runtime_get_sync(&client->dev);
> > 542                if (ret < 0) {
> 
> > 543                        pm_runtime_put_noidle(&client->dev);
> > 544                        goto unlock_and_return;
> 
> Instead of two above:

From the document, pm_runtime_put_noidle is to decrease the runtime PM
usage counter of a device unless it is 0 already; while pm_runtime_put
would additionally run pm_request_idle to turn off the power if usage
counter is zero.

So here maybe we can really use pm_runtime_put instead of
pm_runtime_put_noidle, although it seems that 'pm_runtime_get_sync' and
'pm_runtime_put_noidle' often appear in pairs.

>                        goto err_rpm_put;
> 
> > 545                }
> > 546
> > 547                ret = __ov02a10_start_stream(ov02a10);
> > 548                if (ret) {
> > 549                        __ov02a10_stop_stream(ov02a10);
> > 550                        ov02a10->streaming = !on;
> > 551                        goto err_rpm_put;
> > 552                }
> > 553        } else {
> > 554                __ov02a10_stop_stream(ov02a10);
> > 555                pm_runtime_put(&client->dev);
> > 556        }
> > 557
> > 558        ov02a10->streaming = on;
> 
> (1)
> 
> > 559        mutex_unlock(&ov02a10->mutex);
> > 560
> > 561        return 0;
> > 562
> > 563 err_rpm_put:
> > 564        pm_runtime_put(&client->dev);
> 
> > 565 unlock_and_return:
> 
> Should be moved to (1).
> 
> > 566        mutex_unlock(&ov02a10->mutex);
> > 567
> >
> > Uninitialized scalar variable (UNINIT)
> >     4. uninit_use: Using uninitialized value ret.
> >
> > 568        return ret;
> > 569 }
> >
> > Variable ret has not been initialized, so the error return value is a
> > garbage value. It should be initialized with some appropriate negative
> > error code, or ret could be removed and the return should return a
> > literal value of a error code.
> >
> > I was unsure what value is appropriate to fix this, so instead I'm
> > reporting this issue.
>