From: Grant Likely <grant.likely@secretlab.ca>
To: Anton Vorontsov <cbouatmailru@gmail.com>
Cc: sfr@canb.auug.org.au, devicetree-discuss@lists.ozlabs.org,
microblaze-uclinux@itee.uq.edu.au, jeremy.kerr@canonical.com,
linuxppc-dev@lists.ozlabs.org, "M. Warner Losh" <imp@bsdimp.com>
Subject: Re: [PATCH 6/6] of/device: populate platform_device (of_device) resource table on allocation
Date: Thu, 10 Jun 2010 10:30:26 -0600 [thread overview]
Message-ID: <AANLkTimjIyclTWZZW1A26zOcWroK-bwOkmEqsLm4DINk@mail.gmail.com> (raw)
In-Reply-To: <20100610154741.GA7484@oksana.dev.rtsoft.ru>
On Thu, Jun 10, 2010 at 9:47 AM, Anton Vorontsov <cbouatmailru@gmail.com> w=
rote:
> On Thu, Jun 10, 2010 at 09:13:57AM -0600, M. Warner Losh wrote:
> [...]
>> : >> I told you several ways of how to improve the code (based on
>> : >> the ideas from drivers/base/, so the ideas aren't even mine,
>> : >> fwiw).
>> : >
>> : > I tend to agree with Anton here.
>> :
>> : The reason I'm confident doing it that way is that it is *not* a
>> : structure. =A0There is no structure relationship between the resource
>> : table and the platform_device other than they are allocated with the
>> : same kzalloc() call. =A0All the code that cares about that is containe=
d
>> : within 4 lines of code. =A0I'm resistant to using a structure because =
it
>> : is adds an additional 5-6 lines of code to add a structure that won't
>> : be used anywhere else, and is only 4 lines to begin with.
>>
>> I tend to agree with Grant here. =A0The idiom he's using is very wide
>> spread in the industry and works extremely well. =A0It keeps the
>> ugliness confined to a couple of lines and is less ugly than the
>> alternatives for this design pattern. =A0It is a little surprising when
>> you see the code the first time, granted, but I think its expressive
>> power trumps that small surprise.
>
> Oh, come on. Both constructions are binary equivalent.
>
> So how can people seriously be with *that* code:
>
> =A0 =A0 =A0 =A0dev->resource =3D (void *)&dev[1];
>
> which, semantically, is a nonsense and asks for a fix.
>
> While
> =A0 =A0 =A0 =A0dev_obj->dev.resource =3D dev_obj->resource;
>
> simply makes sense.
Well, my choices are (without whitespace so as not to bias line count):
A)
struct of_device *alloc_function(int num_res)
{
struct device *ofdev;
struct resource *res;
ofdev =3D kzalloc(sizeof(*ofdev) + (sizeof(*res) * num_res), GFP_KERNEL);
if (!ofdev)
return NULL;
res =3D (struct resource *)&ofdev[1];
...
return ofdev;
}
10 lines of code
B)
struct of_device_object {
struct of_device ofdev;
struct resource resource[0];
};
struct of_device *alloc_function(int num_res)
{
struct of_device_object *ofobj;
struct of_device *ofdev;
struct resource *res;
ofobj =3D kzalloc(sizeof(*ofobj) + (sizeof(*res) * num_res), GFP_KERNEL);
if (!ofobj)
return NULL;
res =3D ofobj->resource;
...
return &ofobj->ofdev;
}
15 lines of code
C)
struct of_device *alloc_function(int num_res)
{
struct device *ofdev;
struct resource *res;
ofdev =3D kzalloc(sizeof(*ofdev), GFP_KERNEL)
if (!ofdev)
return NULL;
res =3D kzalloc((sizeof(*res) * num_res), GFP_KERNEL);
if (!res) {
kfree(ofdev); /* or goto an error unwind label */
return NULL;
}
res =3D (struct resource *)&ofdev[1];
...
return ofdev;
}
15 lines of code, plus an extra few lines at kfree(ofdev) time.
When I look at the three, option A is more concise and clearer in it's
intent to me.
That being said, I'm looking at refactoring to use
platform_device_alloc() instead, which is effectively option C. (which
I'd normally avoid, but it removes otherwise duplicate code from
drivers/of).
g.
--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
next prev parent reply other threads:[~2010-06-10 16:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-08 14:26 [PATCH 0/6] OF device code merges and improvements Grant Likely
2010-06-08 14:26 ` [PATCH 1/6] of: Use full node name in resource structures Grant Likely
2010-06-08 14:26 ` [PATCH 2/6] of/device: merge of_device_uevent Grant Likely
2010-06-08 14:26 ` [PATCH 3/6] of: Modify of_device_get_modalias to be passed struct device Grant Likely
2010-06-08 14:26 ` [PATCH 4/6] of/device: Merge of_platform_bus_probe() Grant Likely
2010-06-08 14:26 ` [PATCH 5/6] of: Merge of_device_alloc Grant Likely
2010-06-08 14:26 ` [PATCH 6/6] of/device: populate platform_device (of_device) resource table on allocation Grant Likely
2010-06-08 15:57 ` Anton Vorontsov
2010-06-08 16:02 ` Grant Likely
2010-06-08 16:46 ` Anton Vorontsov
2010-06-08 18:41 ` Grant Likely
2010-06-08 19:48 ` Anton Vorontsov
2010-06-10 6:17 ` Benjamin Herrenschmidt
2010-06-10 14:18 ` Grant Likely
2010-06-10 15:13 ` M. Warner Losh
2010-06-10 15:47 ` Anton Vorontsov
2010-06-10 16:01 ` M. Warner Losh
2010-06-10 16:52 ` Anton Vorontsov
2010-06-10 17:09 ` Mitch Bradley
2010-06-10 17:20 ` Grant Likely
2010-06-10 17:09 ` M. Warner Losh
2010-06-11 1:14 ` Benjamin Herrenschmidt
2010-06-10 16:30 ` Grant Likely [this message]
2010-06-10 17:10 ` Anton Vorontsov
2010-06-10 17:21 ` Grant Likely
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=AANLkTimjIyclTWZZW1A26zOcWroK-bwOkmEqsLm4DINk@mail.gmail.com \
--to=grant.likely@secretlab.ca \
--cc=cbouatmailru@gmail.com \
--cc=devicetree-discuss@lists.ozlabs.org \
--cc=imp@bsdimp.com \
--cc=jeremy.kerr@canonical.com \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=microblaze-uclinux@itee.uq.edu.au \
--cc=sfr@canb.auug.org.au \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).