Message-ID: <20130711202617.GA25003@kroah.com>
Date:	Thu, 11 Jul 2013 13:26:17 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Oliver Schinagl <oliver+list@...inagl.nl>
Cc:	linux-kernel@...r.kernel.org, linux@...ck-us.net,
	khali@...ux-fr.org
Subject: Re: [PATCH v2 2/7] sysfs.h: add ATTRIBUTE_GROUPS() macro

On Thu, Jul 11, 2013 at 10:09:11PM +0200, Oliver Schinagl wrote:
> On 07/11/13 19:06, Greg Kroah-Hartman wrote:
> >On Thu, Jul 11, 2013 at 01:58:29PM +0200, Oliver Schinagl wrote:
> >>On 11-07-13 02:36, Greg Kroah-Hartman wrote:
> >>>To make it easier for driver subsystems to work with attribute groups,
> >>>create the ATTRIBUTE_GROUPS macro to remove some of the repetitive
> >>>typing for the most common use for attribute groups.
> >>But binary groups are discriminated against :(
> >
> >Yes, as they are "rarer" by far, as they should be.  binary sysfs files
> >should almost never be used, as they are only "pass-through" files to
> >the hardware, so I want to see you do more work in order to use them, as
> >they should not be created lightly.
> I guess I can see a valid reason here, but they are only helper
> macro's making life easier for people who do need to use these and
> are on par with the non-binary versions. And we already have quite
> some binary attributes, probably far less then normal ones :)

I only count about 100 valid binary files in the tree at the moment,
that's not really all that many to handle.

> Anyway, wouldn't all users be reviewed anyway? But I guess it's a
> small safety net to make it not TOO easy.

exactly :)

> >>The attached patch should help here.
> >
> >Can you give me an example of using these macros?  I seem to be lost in
> >them somehow, or maybe my morning coffee just hasn't kicked in...
> Yeah, I kinda added the whole shebang there :) I was trying being helpful :(
> 
> >
> >>I suppose one more additional helper wouldn't be bad to have:
> >>
> >>#define ATTRIBUTE_(BIN_)GROUPS_R[O/W](_name(, _size)) \
> >>ATTRIBUTE_(BIN_)ATTR_R[O/W](_name, _size); \
> >>ATTRIBUTE_(BIN_)GROUPS(_name)
> >
> >Would that ever be needed?
> Of ourse, by the lazy :)
> 
> I think now you create an attribute in a group as this (with this patch):
> 
> ATTRIBUTE_ATTR_RO(name, SIZE);

but "raw" attributes are rare, you really want a "device", "class", or
"bus" attribute, right?

> ATTRIBUTE_GROUPS(name);
> 
> .group = name;
> 
> After that last addition, you'd simply do:
> ATTRIBUTE_GROUPS_RO(name);
> 
> .group = name;
> 
> saves a whole line :)

Not worth it :)

> >>>From 003ab7a74ff689daa6934e7bc50c498b2d35a1cc Mon Sep 17 00:00:00 2001
> >>From: Oliver Schinagl <oliver@...inagl.nl>
> >>Date: Thu, 11 Jul 2013 13:48:18 +0200
> >>Subject: [PATCH] sysfs: add more helper macro's for (bin_)attribute(_groups)
> >>
> >>With the recent changes to sysfs there's various helper macro's.
> >>However there's no RW, RO BIN_ helper macro's. This patch adds them.
> >>
> >>Additionally there are no BIN_ group helpers so there's that aswell
> >>Moreso, if both bin and normal attribute groups are used, there's a
> >>simple helper for that, though the naming code be better. _TXT_ for the
> >>show/store ones and neither TXT or BIN for both, but that would change
> >>things to extensivly.
> >>
> >>Finally there's also helpers for ATTRIBUTE_ATTRS.
> >>
> >>After this patch, create default attributes can be as easy as:
> >>
> >>ATTRIBUTE_(BIN_)ATTR_RO(name, SIZE);
> >>ATTRIBUTE_BIN_GROUPS(name);
> >>
> >>Signed-off-by: Oliver Schinagl <oliver@...inagl.nl>
> >>---
> >>  include/linux/sysfs.h | 96 ++++++++++++++++++++++++++++++++++++++++++++-------
> >>  1 file changed, 84 insertions(+), 12 deletions(-)
> >>
> >>diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
> >>index 2c3b6a3..0ebed11 100644
> >>--- a/include/linux/sysfs.h
> >>+++ b/include/linux/sysfs.h
> >>@@ -17,6 +17,7 @@
> >>  #include <linux/list.h>
> >>  #include <linux/lockdep.h>
> >>  #include <linux/kobject_ns.h>
> >>+#include <linux/stat.h>
> >>  #include <linux/atomic.h>
> >>
> >>  struct kobject;
> >>@@ -94,15 +95,32 @@ struct attribute_group {
> >>  #define __ATTR_IGNORE_LOCKDEP	__ATTR
> >>  #endif
> >>
> >>-#define ATTRIBUTE_GROUPS(name)					\
> >>-static const struct attribute_group name##_group = {		\
> >>-	.attrs = name##_attrs,					\
> >>+#define __ATTRIBUTE_GROUPS(_name)				\
> >>+static const struct attribute_group *_name##_groups[] = {	\
> >>+	&_name##_group,						\
> >>+	NULL,							\
> >>+}
> >>+
> >>+#define ATTRIBUTE_GROUPS(_name)					\
> >>+static const struct attribute_group _name##_group = {		\
> >>+	.attrs = _name##_attrs,					\
> >>  };								\
> >>-static const struct attribute_group *name##_groups[] = {	\
> >>-	&name##_group,						\
> >>+__ATTRIBUTE_GROUPS(_name)
> >>+
> >>+#define __ATTRIBUTE_ATTRS(_name)				\
> >>+struct bin_attribute *_name##_attrs[] = {			\
> typo here, scrap bin_ copy paste fail!
> 
> >>+	&_name##_attr,						\
> >>  	NULL,							\
> >>  }
> >>
> >>+#define ATTRIBUTE_ATTR_RO(_name, _size)				\
> >>+struct attribute _name##_attr = __ATTR_RO(_name, _size);	\
> >>+__ATTRIBUTE_ATTRS(_name)
> >>+
> >>+#define ATTRIBUTE_ATTR_RW(_name, _size)				\
> >>+struct attribute _name##_attr = __ATTR_RW(_name, _size);	\
> >>+__ATTRIBUTE_ATTRS(_name)
> >
> >What do these two help out with?  "attribute attribute read-write" seems
> >a bit "clunky", don't you think? :)
> I aggree, but I tried to stick with the ATTRIBUTE_GROUP naming and
> that's the best I could come up with.
> 
> Unless I completely misunderstood (which isn't all that unlikely)
> the following is needed to create a group using a .group.
> 
> So you pass group an array of attribute_group pointers. The
> ATTRIBUTE_GROUPS helps there, right? It saves the typing of creating
> the array of groups and adding groups to that.
> 
> So a group consists of an array of attributes if I understood right
> and that array needs to be filled with pointers attributes? well
> those ATTRIBUTE_ATTR's do just that. Granted, maybe the naming is
> poor, but just ATTRS() felt to short.

Here's an example of a file I converted to use the ATTRIBUTE_GROUP()
macro attached below (net/wireless/sysfs).  As is, it's an increase of
only 2 lines to the file overall, which is about normal for the
conversion.  As you can see, you still need a list of attributes (which
someone has already said I need another macro for, to stop typing
"&dev_attr*.attr" all the time).

With your macros, how would a file be converted to use them?  Perhaps
that will help explain things to me better.


> >>+#define ATTRIBUTE_BIN_GROUPS(_name)					\
> >>+static const struct attribute_group _name##_bin_group = {		\
> >>+	.bin_attrs = _name##_bin_attrs,					\
> >>+};									\
> >>+__ATTRIBUTE_BIN_GROUPS(_name)
> This is the equiv. of ATTRIBUTE_GROUPS(_name) which creates an
> attribute group, with only a binary attribute instead.

Again, binary files are rare, and should be rare, don't make it too easy
to create them :)

> >>+#define ATTRIBUTE_BIN_ATTR_RW(_name, _size)				\
> >>+struct bin_attribute _name##_bin_attr = __BIN_ATTR_RW(_name, _size);	\
> >>+__ATTRIBUTE_BIN_ATTRS(_name)
> These I guess are the equivialent what ATTRIBUTE_GROUP is for
> groups, but now for the attributes that go in groups?
> 
> >
> >Can you show me how these would be used in a real-world example?
> Well my real world is currently limited by my own driver. If I may
> copy paste from there:
> 
> ATTRIBUTE_BIN_ATTR_RO(sunxi_sid, SID_SIZE);
> ATTRIBUTE_BIN_GROUPS(sunxi_sid);
> 
> static struct platform_driver sunxi_sid_driver = {
> 	.probe = sunxi_sid_probe,
> 	.remove = sunxi_sid_remove,
> 	.driver = {
> 		.name = DRV_NAME,
> 		.owner = THIS_MODULE,
> 		.of_match_table = sunxi_sid_of_match,
> 		.groups = sunxi_sid_bin_groups,
> 	},
> };
> module_platform_driver(sunxi_sid_driver);
> 
> But if you say, you want to be a little less complete, we can drop
> ATTRIBUTE_BIN_ATTR_R[OW]() forcing you to do this instead:
> 
> struct bin_attribute sunxi_sid_bin_attr = __BIN_ATTR_RO(eeprom, SID_SIZE);
> 
> struct bin_attribute *sunxi_sid_bin_attrs[] = {
> 	&sunxi_sid_bin_attr,
> 	NULL,
> };
> 
> Which requires some manual labor yet still has the __BIN_ATTR_R[OW]
> macro's to help with some of the more tedious work and allowing you
> to name the binary attributes nicer?

BIN_ATTR_RO() is fine, I'd stick with that for now, it's getting
confusing enough as-is :)

thanks,

greg k-h
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