linux-kernel - Re: [PATCH] Declare the file

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Message-ID: <CAPGkw+xQCwRU8Bw97-x5Qf1v2Bncq7tC9ksXznezefYZQSxCGg@mail.gmail.com>
Date:   Sun, 29 Aug 2021 04:16:13 +0200
From:   Krish Jain <krishjain02939@...il.com>
To:     Bryan Brattlof <hello@...anbrattlof.com>
Cc:     linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev
Subject: Re: [PATCH] Declare the file_operations struct as const

Sorry, I meant I ran "make CCFLAGS=-Werror W=1
M=drivers/staging/android"  and I get no error.

On Sun, Aug 29, 2021 at 4:13 AM Krish Jain <krishjain02939@...il.com> wrote:
>
> On Sat, Aug 28, 2021 at 1:38 AM Bryan Brattlof <hello@...anbrattlof.com> wrote:
> >
> > Hi Krish!
> >
> > I'm sure someone has said something by now, however "top posting", where
> > you reply to emails by writing on the top can make things hard to read
> > on the mailing lists. The conversation is upside down when reading.
> >
> >    https://en.wikipedia.org/wiki/Posting_style#Top-posting
> >
> > Next time try writing underneath the text your referring to like this:
> > Don't worry we're all learning here :)
> >
> > On this day, August 27, 2021 thus sayeth Krish Jain:
> > > I unfortunately forgot to add Greg to this thread. Doing so now. I
> > > apologize for the confusion, if any. This patch was regarding the
> > > staging tree's file android/ashmem.c and declaring the file_operations
> > > struct as const as done elsewhere in the kernel, because there are no
> > > modifications to its fields.
> > >
> > > Warm Regards
> > >
> >
> > Things can be a little deceiving in the kernel. That's why testing your
> > changes before you submit them can be helpful.
> >
> > But don't worry too much if you break something, there are countless
> > bots trying to break the kernel every day. It usually means you're
> > learning when you break something.
> >
> > >
> > > On Fri, Aug 27, 2021 at 8:38 PM Krish Jain <krishjain02939@...il.com> wrote:
> > > >
> > > > So what do you think I can do?
> > > >
> > > > Best Regards
> > > >
> >
> > That's a tough one as it really depends on your situation. When I first
> > started programming I had a *really* old (even for that time) laptop
> > that couldn't do much.  It wasn't ideal but I found I could connect
> > through ssh to a virtual machine my university lent me to "learn to
> > code".
> >
> > I have no idea what your situation is like. Though having a second
> > computer to compile code while I wrote worked for me.
> >
> > > >
> > > > On Fri, Aug 27, 2021 at 10:50 AM Krish Jain <krishjain02939@...il.com> wrote:
> > > > >
> > > > > Hi, yes, this is my first time programming at this low level. And yes,
> > > > > I read both docs now. Furthermore the issue is that my current
> > > > > hardware can't handle building the kernel, it barely managed to
> > > > > survive the first build after 2 hours so I don't know how I can. If I
> > > > > change it to static const would it fix the issue and build
> > > > > successfully?  If not what would be the error message, then I can
> > > > > debug. Thanks
> > > > >
> >
> > As for your patch, I built the driver using:
> >
> >   $ make CCFLAGS=-Werror W=1 M=drivers/staging/android
> >
> > Which produced the following error:
> >
> >
> > drivers/staging/android/ashmem.c: In function ‘ashmem_mmap’:
> > drivers/staging/android/ashmem.c:380:2: warning: ‘static’ is not at beginning of declaration [-Wold-style-declaration]
> >   380 |  const static struct file_operations vmfile_fops;
> >       |  ^~~~~
> > drivers/staging/android/ashmem.c:431:16: error: assignment of read-only variable ‘vmfile_fops’
> >   431 |    vmfile_fops = *vmfile->f_op;
> >       |                ^
> > drivers/staging/android/ashmem.c:432:21: error: assignment of member ‘mmap’ in read-only object
> >   432 |    vmfile_fops.mmap = ashmem_vmfile_mmap;
> >       |                     ^
> > drivers/staging/android/ashmem.c:433:34: error: assignment of member ‘get_unmapped_area’ in read-only object
> >   433 |    vmfile_fops.get_unmapped_area =
> >       |                                  ^
> > make[1]: *** [scripts/Makefile.build:271: drivers/staging/android/ashmem.o] Error 1
> > make: *** [Makefile:1851: drivers/staging/android] Error 2
> >
>
> Hi, this seems very useful and I tried this myself just now. I don't
> get any errors that you do though. When I hit enter I just get a new
> shell prompt. What am I doing wrong? Probably a silly mistake. I ran
> make CCFLAGS=-Werror M=drivers/staging/android/.
>
>
> - Krish
>
> > You shouldn't need to compile the entire kernel. That may be why your
> > computer is having a hard time?
> >
> > Hope this helps :) and it was nice to meet you Krish
> > ~Bryan
> >