Re: [RFC/PATCH 0/5] read/write on attribute w/o show/store should return -ENOSYS

From: Chris Wright
Date: Thu Apr 28 2005 - 12:41:40 EST

* Greg KH (gregkh@xxxxxxx) wrote:
> On Thu, Apr 28, 2005 at 12:30:09AM -0500, Dmitry Torokhov wrote:
> > Hi,
> >
> > Jean Delvare has noticed that if a driver happens to declare its
> > attribute as RW but doesn't provide store() method attempt to write
> > into such attribute will cause spinning process as most of the
> > attribute implementations return 0 in case of missing store causing
> > endless retries. In some cases missing show/store will return -EPERM,
> >
> > I think we should unify implementations and have them all return -ENOSYS
> > (function not implemented) when corresponding method (show/store) is
> > missing.
> What is the POSIX standard for this? ENOSYS or EACCESS?

SuSv3 suggests EBADF, however we already do EINVAL at VFS for no write
op. Although, returning 0 (i.e. wrote zero bytes) is still meaningful

> Or anyone have a link that I can look this up at?

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