From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <4EE87755.3000000@metafoo.de> Date: Wed, 14 Dec 2011 11:15:49 +0100 From: Lars-Peter Clausen MIME-Version: 1.0 To: Greg KH CC: Greg Kroah-Hartman , Jonathan Cameron , devel@driverdev.osuosl.org, linux-iio@vger.kernel.org Subject: Re: [PATCH] staging:iio: Add wrapper functions around buffer access ops References: <1323684526-11134-1-git-send-email-lars@metafoo.de> <20111213004506.GA11553@kroah.com> <4EE7145F.9040003@metafoo.de> <20111213235926.GA23916@kroah.com> In-Reply-To: <20111213235926.GA23916@kroah.com> Content-Type: text/plain; charset=ISO-8859-1 List-ID: On 12/14/2011 12:59 AM, Greg KH wrote: > >>>> +static inline int buffer_get_length(struct iio_buffer *buffer) >>>> +{ >>>> + if (buffer->access->get_length) >>>> + return buffer->access->get_length(buffer); >>>> + >>>> + return -ENOSYS; >>> >>> Here you return an error, but why ENOSYS? >>> >>> Consistancy is key, and you don't have it here at all. Or if you do, I >>> sure don't understand it... >> >> Well, different types of functions require different semantics. While the >> previous ones did either return 0 in case of success or a error value in case >> of an error, buffer_get_length returns an integer value where 0 is a valid >> value. Since we can't make any meaningful assumptions about the buffer size if >> the callback is not implemented we return an error value. Why ENOSYS? Because >> it is the code for 'function not implemented' and is used throughout the kernel >> in similar situations. > > Is the caller always supposed to check this? If so, please mark the > function as such so the compiler will complain if it isn't. Marking the function as __must_check doesn't make much sense here. Since it will either return an error or the buffer length. So you'll always use the returned result one way or the other.