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

From: Ojaswin Mujoo <ojaswin98@gmail.com>
To: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
	nsaenz@kernel.org, gregkh@linuxfoundation.org, arnd@arndb.de,
	phil@raspberrypi.com, bcm-kernel-feedback-list@broadcom.com,
	linux-arm-kernel@lists.infradead.org,
	linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: staging: vc04_services: Need suggestions on trying to fix sparse warning in vchiq_arm.c
Date: Sun, 6 Jun 2021 14:56:32 +0530	[thread overview]
Message-ID: <20210606092601.GA6609@ojas> (raw)
In-Reply-To: <57aa6e2b-0267-664d-539a-e82000928101@i2se.com>

On Sat, Jun 05, 2021 at 10:41:17AM +0200, Stefan Wahren wrote:
> 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
Hey Stefan,

Ahh got it. sure I can get a 3B+ instead, thanks for the heads up.
> 
> >
> > 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@lists.infradead.org
> >>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > _______________________________________________
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> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

Regards,
Ojaswin