linux-kernel - Re: [PATCH] Don't test for NULL firmware before releasing

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Message-ID: <b21541c5-f55d-d33e-9310-6db5ccb08b25@kapsi.fi>
Date:   Fri, 17 Feb 2023 14:04:10 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>,
        Jesper Juhl <jesperjuhl76@...il.com>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Jonathan Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH] Don't test for NULL firmware before releasing

On 2/16/23 15:19, Stanislaw Gruszka wrote:
> Hi
> 
> On Thu, Feb 16, 2023 at 02:37:15AM +0100, Jesper Juhl wrote:
>>  From 4fe34831e2e7677b1c9616356f0a2e0a36ec092f Mon Sep 17 00:00:00 2001
>> From: Jesper Juhl <jesperjuhl76@...il.com>
>> Date: Thu, 16 Feb 2023 02:33:05 +0100
>> Subject: [PATCH] Don't test for NULL firmware before releasing
>>
>> release_firmware() tests for a NULL pointer itself, no need to do it up-front.
>>
>> Signed-off-by: Jesper Juhl <jesperjuhl76@...il.com>
>>
>> ---
>>   drivers/gpu/drm/tegra/falcon.c | 3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/tegra/falcon.c b/drivers/gpu/drm/tegra/falcon.c
>> index c0d85463eb1a..ae599441f031 100644
>> --- a/drivers/gpu/drm/tegra/falcon.c
>> +++ b/drivers/gpu/drm/tegra/falcon.c
>> @@ -153,8 +153,7 @@ int falcon_init(struct falcon *falcon)
>>
>>   void falcon_exit(struct falcon *falcon)
>>   {
>> -	if (falcon->firmware.firmware)
>> -		release_firmware(falcon->firmware.firmware);
>> +       	release_firmware(falcon->firmware.firmware);
> 
> Please check patches with checkpatch.pl before posting.
> 
> Regards
> Stanislaw
> 

Aside the formatting deficiencies, I'm also not in favor of relying on 
NULL checks inside callees since doing so removes contextual information 
from the programmer; just looking at the code, it is easy to assume the 
pointer cannot be NULL if there is no NULL check. Recently had a longer 
thread about this in the context of kfree in TegraDRM.

Thanks
Mikko