Re: [PATCH v2 2/7] sysfs.h: add ATTRIBUTE_GROUPS() macro

From: Oliver Schinagl
Date: Sun Jul 14 2013 - 18:55:40 EST

Greg,

Haven't heard anything about this v2 patch, I know you are very busy but with the merge window closing today/yesterday just wondering about the status of it all.

Oliver

On 11-07-13 22:55, Oliver Schinagl wrote:
On 07/11/13 22:26, Greg Kroah-Hartman wrote:
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.
100 is quite a few :) But point taken.

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

exactly :)
I aggree and this is a v2 that strips all the additional bits.

A few comments left below.


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?
I suppose so, But I got stuck in the rare case some how initially. I registered my driver with module_platform_driver(); and in that struct i had the "device_driver" which had a group attribute so I used that. I already learned from maxime that that is the wrong way :) and hopefully I'll figure out what the right way will be soon ;)


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@xxxxxxxxxxx>
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@xxxxxxxxxxx>
---
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.
Heh, they can't I don't think.



+#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 :)
Agreed and attached.


thanks,

greg k-h



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