linux-kernel - Re: staging: vc04_services: Need suggestions on trying to fix sparse warning in vchiq_arm.c

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Message-ID: <57aa6e2b-0267-664d-539a-e82000928101@i2se.com>
Date:   Sat, 5 Jun 2021 10:41:17 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Ojaswin Mujoo <ojaswin98@...il.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>, nsaenz@...nel.org,
        gregkh@...uxfoundation.org, arnd@...db.de, phil@...pberrypi.com,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: staging: vc04_services: Need suggestions on trying to fix sparse
 warning in vchiq_arm.c

Hi Ojaswin,

Am 05.06.21 um 09:23 schrieb Ojaswin Mujoo:
> On Fri, Jun 04, 2021 at 08:13:06AM +0200, Stefan Wahren wrote:
>> Hi Ojaswin,
>>
>> Am 02.06.21 um 16:50 schrieb Ojaswin Mujoo:
>>> On Tue, Jun 01, 2021 at 11:23:07PM +0300, Dan Carpenter wrote:
>>>> The problem is not the Sparse warning, the problem is that this code is
>>>> a mess.  It used to very clearly buggy and I reported the bug.  I think
>>>> Arnd found the bug again independently and fixed it.
>>>>
>>>> A couple weeks ago Al Viro looked at this code.  Here is his write up:
>>>>
>>>> https://www.spinics.net/lists/kernel/msg3952745.html
>>>>
>>>> It shouldn't take Al Viro dozens of pages of detailed analysis to try
>>>> figure out if the code is safe or not.  Your idea silences the warning
>>>> but would make the code even more subtle and complicated.
>>>>
>>>> The right thing to do is to re-write the code to be simpler.
>>>>
>>>> regards,
>>>> dan carpenter
>>>>
>>> Thank you for the prompt reply and the link, it was very insightful. You
>>> are right, I was definitely going about this the wrong way and missing
>>> the larger picture. I'll spend some time trying to understand this
>>> codebase as I think that'd be a good start to understand how stuff works in
>>> the kernel (even though some of the things in this driver are anti patterns)
>>> and hopefully get some ideas on ways to clean this up.
>>>
>>> Anyways, thanks again for the help, cheers!
>> thanks for your interest in cleaning this up. Yes, it's not clear which
>> points on the TODO list are the lower hanging fruits. In case you don't
>> want to fix checkpatch issues, maybe you can look at points 8, 9, 10, 12
>> and 13. Most of them require testing with a Raspberry Pi, but feel free
>> to ask if you have problems with it.
>>
>> Regards
>> Stefan
>>
> Got it, Task 10 (cdev to its own file) seems like a pretty good task to
> get started with. I'm planning to buy a Rpi 4 so I think I can run tests
> on that. 

okay, but the AFAIK the vchiq driver in the mainline kernel doesn't work
with Rpi 4 yet. The Raspberry Pi 3 B Plus is currently the recommend
devel platform, so you can test 32 and 64 bit kernel.

Best regards

>
> Thank you so much for the help, I'll get back incase I face any issues down 
> the line.
>
> Regards,
> Ojaswin
>
>>> Ojaswin
>>>
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>>> linux-arm-kernel@...ts.infradead.org
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