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Date:   Sun, 29 Aug 2021 08:16:55 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Krish Jain <krishjain02939@gmail.com>
Cc:     Bryan Brattlof <hello@bryanbrattlof.com>,
        linux-kernel@vger.kernel.org, linux-staging@lists.linux.dev
Subject: Re: [PATCH] Declare the file_operations struct as const
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On Sun, Aug 29, 2021 at 04:13:43AM +0200, Krish Jain wrote:
> On Sat, Aug 28, 2021 at 1:38 AM Bryan Brattlof <hello@bryanbrattlof.com> wrote:
> > 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/.

Are you sure the file is being built at all?  You usually have to select
the proper configuration option to enable that driver as well.

thanks,

greg k-h