From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [RFC PATCH v2 3/3] i2c: show and change bus frequency via sysfs Date: Wed, 15 Oct 2014 06:13:54 -0700 Message-ID: <543E7312.1020104@roeck-us.net> References: <1413298094-9276-1-git-send-email-octavian.purdila@intel.com> <1413298094-9276-4-git-send-email-octavian.purdila@intel.com> <20141014154151.GB10067@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Octavian Purdila Cc: Wolfram Sang , Johan Hovold , linux-i2c , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lkml List-Id: linux-i2c@vger.kernel.org On 10/15/2014 04:49 AM, Octavian Purdila wrote: > On Tue, Oct 14, 2014 at 6:41 PM, Guenter Roeck wrote: >> >> On Tue, Oct 14, 2014 at 05:48:14PM +0300, Octavian Purdila wrote: >>> This patch adds three new sysfs files: bus_frequency, >>> bus_min_frequency and bus_max_frequency which allows the user to view >>> or change the bus frequency on a per bus level. >>> > > > >>> + >>> +static DEVICE_ATTR(bus_frequency, S_IRUGO, i2c_sysfs_freq_show, >>> + i2c_sysfs_freq_store); >> >> Consider using DEVICE_ATTR_RO here. Also, extra empty line. >> > > Unfortunately that won't work because we must transform bus_frequency > to a RW entry (via is_visible) if the bus can change the frequency. We Ah yes, you are right. > can't use DEVIE_ATTR_RW either, because transforming a RW entry to a > RO entry with is visible is not possible: > Why not ? is_visible returns the desired mode. Just like you can return mode | S_IWUSR, you can return mode & ~S_IWUSR. Am I missing something ? Guenter