Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934569AbbDWMjc (ORCPT ); Thu, 23 Apr 2015 08:39:32 -0400 Received: from mail-wg0-f49.google.com ([74.125.82.49]:36538 "EHLO mail-wg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934251AbbDWMj0 convert rfc822-to-8bit (ORCPT ); Thu, 23 Apr 2015 08:39:26 -0400 Subject: Re: [PATCH v2 3/4] of: overlay: Add sysfs attributes Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2070.6\)) Content-Type: text/plain; charset=utf-8 From: Pantelis Antoniou In-Reply-To: <20150423123346.GA19166@kroah.com> Date: Thu, 23 Apr 2015 15:39:21 +0300 Cc: Rob Herring , Grant Likely , Andrew Morton , Matt Porter , Koen Kooi , Guenter Roeck , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" Content-Transfer-Encoding: 8BIT Message-Id: <98237E9E-04CB-4CD5-8B2F-63F070B54459@konsulko.com> References: <1428434632-13789-1-git-send-email-pantelis.antoniou@konsulko.com> <1428434632-13789-4-git-send-email-pantelis.antoniou@konsulko.com> <6E391B8F-936A-4FD1-B8CC-C9B5FCE0B291@konsulko.com> <20150423123346.GA19166@kroah.com> To: Greg KH X-Mailer: Apple Mail (2.2070.6) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6001 Lines: 183 Hi Greg, > On Apr 23, 2015, at 15:33 , Greg KH wrote: > > On Thu, Apr 23, 2015 at 03:00:03PM +0300, Pantelis Antoniou wrote: >> Hi Rob, >> >>> On Apr 15, 2015, at 04:27 , Rob Herring wrote: >>> >>> On Tue, Apr 7, 2015 at 2:23 PM, Pantelis Antoniou >>> wrote: >>>> Implement a number of sysfs attributes for overlays. >>>> >>>> * A throw once master enable switch to protect against any >>>> further overlay applications if the administrator desires so. >>> >>> This one should be a separate patch. >>> >> >> OK. >> >>>> * A per overlay targets sysfs attribute listing the targets of >>>> the installed overlay. >>> >>> What are targets? "targets lists targets" does not help me. The >>> documentation doesn't help me either. >>> >> >> It lists the targets of the overlay that has been applied. What do >> you need in order to be helped? I mean what do you want listed? >> >>>> * A per overlay can_remove sysfs attribute that reports whether >>>> the overlay can be removed or not due to another overlapping overlay. >>>> >>>> Signed-off-by: Pantelis Antoniou >>>> --- >>>> drivers/of/overlay.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++++++- >>>> 1 file changed, 166 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c >>>> index f17f5ef..c54d097 100644 >>>> --- a/drivers/of/overlay.c >>>> +++ b/drivers/of/overlay.c >>>> @@ -21,6 +21,7 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> >>>> #include "of_private.h" >>>> >>>> @@ -55,8 +56,12 @@ struct of_overlay { >>>> struct kobject kobj; >>>> }; >>>> >>>> +/* master enable switch; once set to 0 can't be re-enabled */ >>>> +static atomic_t ov_enable = ATOMIC_INIT(1); >>>> + >>>> static int of_overlay_apply_one(struct of_overlay *ov, >>>> struct device_node *target, const struct device_node *overlay); >>>> +static int overlay_removal_is_ok(struct of_overlay *ov); >>>> >>>> static int of_overlay_apply_single_property(struct of_overlay *ov, >>>> struct device_node *target, struct property *prop) >>>> @@ -345,6 +350,144 @@ static struct kobj_type of_overlay_ktype = { >>>> >>>> static struct kset *ov_kset; >>>> >>>> +static ssize_t enable_read(struct file *filp, struct kobject *kobj, >>>> + struct bin_attribute *bin_attr, char *buf, >>>> + loff_t offset, size_t count) >>>> +{ >>>> + char tbuf[3]; >>>> + >>>> + if (offset < 0) >>>> + return -EINVAL; >>>> + >>>> + if (offset >= sizeof(tbuf)) >>>> + return 0; >>>> + >>>> + if (count > sizeof(tbuf) - offset) >>>> + count = sizeof(tbuf) - offset; >>>> + >>>> + /* fill in temp */ >>>> + tbuf[0] = '0' + atomic_read(&ov_enable); >>>> + tbuf[1] = '\n'; >>>> + tbuf[2] = '\0'; >>>> + >>>> + /* copy to buffer */ >>>> + memcpy(buf, tbuf + offset, count); >>>> + >>>> + return count; >>>> +} >>>> + >>>> +static ssize_t enable_write(struct file *filp, struct kobject *kobj, >>>> + struct bin_attribute *bin_attr, char *buf, >>>> + loff_t off, size_t count) >>>> +{ >>>> + unsigned int new_enable; >>>> + >>>> + if (off != 0 || (buf[0] != '0' && buf[0] != '1')) >>>> + return -EINVAL; >>>> + >>>> + new_enable = (unsigned int)(buf[0] - '0'); >>>> + if (new_enable > 1) >>>> + return -EINVAL; >>>> + >>>> + /* NOP for same value */ >>>> + if (new_enable == atomic_read(&ov_enable)) >>>> + return count; >>>> + >>>> + /* if we've disabled it, no going back */ >>>> + if (atomic_read(&ov_enable) == 0) >>>> + return -EPERM; >>>> + >>>> + atomic_set(&ov_enable, new_enable); >>>> + return count; >>>> +} >>>> + >>>> +/* just a single char + '\n' + '\0' */ >>>> +static BIN_ATTR_RW(enable, 3); >>> >>> Why are you using bin attribute? You are complicating the >>> implementation needlessly. >>> >> >> It’s the same reason that the device tree core is using it. > > It is doing that for "raw" device tree files, not individual attributes, > right? > Each property of a device tree is a binary attribute. >> Believe it or not, this is the simplest way to do it. >> If you take a look at the sysfs attribute implementation, the binary >> implementation is the one that’s using the least amount of code. > > Then something is really wrong here. > >> To use a non-binary method we have to register per ktype sysfs_ops >> and duplicate the way the non-binary attribute works. > > really? Again, something must be wrong. > >> For the gory details look at sysfs_add_file_mode_ns() in fs/sysfs/file.c >> >> I can add the sysfs_ops but that’s going to be more complicated not less. > Please take a look in linux/sysfs.h. The non-binary sysfs accessors are all using some kind of other kobj; for instance DEVICE_ATTR is using a device_attribute, etc. For the overlay case, I’d have to create a of_overlay_attribute and work from there. > Only use binary sysfs files if you are accepting binary data directly > from userspace and using it as a "pass-through" to the kernel. > > Otherwise just use a "normal" sysfs file. I don't understand the > problem here, sysfs shouldn't be hard to use for simple attributes, that > was not the goal here at all. > There is no generic (i.e. not kobj type specific), non-binary sysfs file interface right now. I can add one for my case, but that’s more code. It’s your call. > thanks, > > greg k-h Regards — Pantelis -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/