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Date:   Sat, 31 Aug 2019 16:44:48 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Christoph Hellwig <hch@lst.de>,
        Matthew Wilcox <willy@infradead.org>,
        linux-fsdevel@vger.kernel.org,
        Octavian Purdila <octavian.purdila@intel.com>,
        Pantelis Antoniou <pantelis.antoniou@konsulko.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Kai =?iso-8859-1?Q?M=E4kisara?= <Kai.Makisara@kolumbus.fi>,
        linux-scsi@vger.kernel.org
Subject: Re: [RFC] Re: broken userland ABI in configfs binary attributes
Message-ID: <20190831144447.GA600@lst.de>
References: <20190826024838.GN1131@ZenIV.linux.org.uk> <20190826162949.GA9980@ZenIV.linux.org.uk> <20190826182017.GE15933@bombadil.infradead.org> <20190826192819.GO1131@ZenIV.linux.org.uk> <20190831083241.GC28527@lst.de> <20190831133537.GX1131@ZenIV.linux.org.uk>
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On Sat, Aug 31, 2019 at 02:35:37PM +0100, Al Viro wrote:
> > So for the one real life example of the configfs attribute life
> > actually is simpler.  acpi_table_aml_write verifies early on that
> > the size matches what it expects.  So if we document that any future
> > instance needs to be able to do that as well we should be able to
> > get away with just writing it from ->flush.
> 
> I'm not sure I understand what you mean...  Do you want them to recognize
> incomplete data and quietly bugger off when called on too early ->flush()?

That is what the only user does anyway, take a look at
acpi_table_aml_write.  So yes, change the documentation to say it
gets written on every close, and the implementation has to deal with
incomplete data by either returning an error or ignoring it.