Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934486AbbDWMd5 (ORCPT ); Thu, 23 Apr 2015 08:33:57 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:33445 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755675AbbDWMdv (ORCPT ); Thu, 23 Apr 2015 08:33:51 -0400 X-Sasl-enc: A/PFowgyS/QTL5/P26J3cB24khm2rsZcWbSm6qQBNmDo 1429792428 Date: Thu, 23 Apr 2015 14:33:46 +0200 From: Greg KH To: Pantelis Antoniou 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" Subject: Re: [PATCH v2 3/4] of: overlay: Add sysfs attributes Message-ID: <20150423123346.GA19166@kroah.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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6E391B8F-936A-4FD1-B8CC-C9B5FCE0B291@konsulko.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5363 Lines: 157 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? > 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. 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. thanks, greg k-h -- 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/