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Date: Mon, 7 Aug 2017 09:08:49 +0300
From: Mikko Rapeli <mikko.rapeli@iki.fi>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        linux-scsi@vger.kernel.org
Subject: Re: [PATCH v06 04/36] uapi scsi/scsi_netlink_fc.h: use __u16, __u32
 and __u64 from linux/types.h
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On Sun, Aug 06, 2017 at 03:09:21PM -0700, James Bottomley wrote:
> On Sun, 2017-08-06 at 23:42 +0300, Mikko Rapeli wrote:
> > Hi,
> > 
> > On Sun, Aug 06, 2017 at 11:22:53AM -0700, James Bottomley wrote:
> > > 
> > > On Sun, 2017-08-06 at 18:43 +0200, Mikko Rapeli wrote:
> > > > 
> > > > Fixes userspace compilation errors like:
> > > > 
> > > > scsi/scsi_netlink_fc.h:60:2: error: expected specifier-qualifier-
> > > > list  before ‘uint64_t’
> > > 
> > > Rather than patching the kernel, why not #include <stdint.h> in
> > > your userspace programme?
> > 
> > The userspace program is actually a test which checks that uapi
> > headers compile alone because several headers are not compiling at
> > all and/or require special tricks. The test is available here:
> > 
> > http://marc.info/?l=linux-kernel&m=150203944104544&w=2
> 
> But you don't seem to be detecting or fixing an existing problem.
>  These types are width unambiguous and all current consumers of these
> headers include stdint.h so you're churning the kernel for a problem
> which doesn't currently exist for any consumer of this header.

The header file dependencies of scsi/scsi_netlink_fc.h are not explicit.
I will propose a patch which includes <stdint.h> in userspace then.

> I can agree not adding any more external uint<x>_t types for newly
> exported headers so new consumers don't depend on an external standard
> is reasonable, so checkpatch should warn if someone tries to add them;
> I just don't see the benefit of going over the whole kernel changing
> stuff that has worked fine for years.  Now if you can tell me there's
> an actual bug somewhere, that's different ...

Tools parsing and checking uapi headers need to be able to compile them
and thus need the explicit list of dependencies. If <stdint.h> is a
required dependency, then scsi/scsi_netlink_fc.h should include it.

scsi/scsi_netlink_fc.h is one of 42 problematic headers left in current
kernel and I want to fix it one way or the other.

-Mikko