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Message-ID: <fe7da2c1-904e-ee4f-9a6c-443049c214b7@quicinc.com>
Date:   Tue, 18 Apr 2023 14:46:33 -0600
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Subject: Re: [PATCH] accel/qaic: initialize ret variable to 0
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To:     Tom Rix <trix@redhat.com>, <ogabbay@kernel.org>,
        <nathan@kernel.org>, <ndesaulniers@google.com>,
        <jacek.lawrynowicz@linux.intel.com>, <quic_carlv@quicinc.com>,
        <stanislaw.gruszka@linux.intel.com>, <quic_pkanojiy@quicinc.com>
CC:     <linux-arm-msm@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
        <linux-kernel@vger.kernel.org>, <llvm@lists.linux.dev>
References: <20230418192046.3235870-1-trix@redhat.com>
From:   Jeffrey Hugo <quic_jhugo@quicinc.com>
In-Reply-To: <20230418192046.3235870-1-trix@redhat.com>
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On 4/18/2023 1:20 PM, Tom Rix wrote:
> clang static analysis reports
> drivers/accel/qaic/qaic_data.c:610:2: warning: Undefined or garbage
>    value returned to caller [core.uninitialized.UndefReturn]
>          return ret;
>          ^~~~~~~~~~
> 
> The ret variable is only set some of the time but is always returned.
> So initialize ret to 0.

This does not appear to be entirely accurate to me.

Do you know what analysis Clang is doing?  Is it limited to the function 
itself?

remap_pfn_range, which initializes ret, will always run at-least once.

Feels more accurate to say that Clang cannot detect that ret will be 
initialized, and we want to quiet the warning from the false positive.

> Fixes: ff13be830333 ("accel/qaic: Add datapath")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>   drivers/accel/qaic/qaic_data.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
> index c0a574cd1b35..b46a16fb3080 100644
> --- a/drivers/accel/qaic/qaic_data.c
> +++ b/drivers/accel/qaic/qaic_data.c
> @@ -591,7 +591,7 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc
>   	struct qaic_bo *bo = to_qaic_bo(obj);
>   	unsigned long offset = 0;
>   	struct scatterlist *sg;
> -	int ret;
> +	int ret = 0;
>   
>   	if (obj->import_attach)
>   		return -EINVAL;