linux-kernel - Re: [PATCH] drivers: base: add cpu_device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <53F734F0.1080401@arm.com>
Date:	Fri, 22 Aug 2014 13:17:52 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	David Herrmann <dh.herrmann@...il.com>
CC:	Sudeep Holla <sudeep.holla@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Stephen Boyd <sboyd@...eaurora.org>, Kay Sievers <kay@...y.org>
Subject: Re: [PATCH] drivers: base: add cpu_device_create to support per-cpu
 devices



On 22/08/14 12:37, David Herrmann wrote:
> Hi
>
> On Fri, Aug 22, 2014 at 1:29 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>> From: Sudeep Holla <sudeep.holla@....com>
>>
>> This patch adds a new function to create per-cpu devices.
>> This helps in:
>> 1. reusing the device infrastructure to create any cpu related
>>     attributes and corresponding sysfs instead of creating and
>>     dealing with raw kobjects directly
>> 2. retaining the legacy path(/sys/devices/system/cpu/..) to support
>>     existing sysfs ABI
>> 3. avoiding to create links in the bus directory pointing to the
>>     device as there would be per-cpu instance of these devices with
>>     the same name since dev->bus is not populated to cpu_sysbus on
>>     purpose
>>
>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> ---
>>   drivers/base/cpu.c  | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/cpu.h |  4 ++++
>>   2 files changed, 58 insertions(+)
>>
>> Hi Greg,
>>
>> Here is the alternate solution I could come up with instead of
>> creating cpu class. cpu_device_create is very similar to
>> device_create_groups_vargs w/o class support, but I could not
>> reuse anything else to avoid creating similar function.
>>
>> Let me know your thoughts/suggestions on this.
>>
>> Regards,
>> Sudeep
>>
>>
>> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
>> index 277a9cfa9040..53f0c4141d05 100644
>> --- a/drivers/base/cpu.c
>> +++ b/drivers/base/cpu.c
>> @@ -363,6 +363,60 @@ struct device *get_cpu_device(unsigned cpu)
>>   }
>>   EXPORT_SYMBOL_GPL(get_cpu_device);
>>
>> +static void device_create_release(struct device *dev)
>> +{
>> +       kfree(dev);
>> +}
>> +
>> +static struct device *
>> +__cpu_device_create(struct device *parent, void *drvdata,
>> +                   const struct attribute_group **groups,
>> +                   const char *fmt, va_list args)
>> +{
>> +       struct device *dev = NULL;
>> +       int retval = -ENODEV;
>> +
>> +       dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>> +       if (!dev) {
>> +               retval = -ENOMEM;
>> +               goto error;
>> +       }
>> +
>> +       device_initialize(dev);
>> +       dev->parent = parent;
>> +       dev->groups = groups;
>> +       dev->release = device_create_release;
>> +       dev_set_drvdata(dev, drvdata);
>> +
>> +       retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
>> +       if (retval)
>> +               goto error;
>> +
>> +       retval = device_add(dev);
>> +       if (retval)
>> +               goto error;
>
> Exactly! As I said, simply setting dev->groups before calling device_add().
>
> However, I really don't understand why we need this as global API.

Yes right now it's used only in cacheinfo. The main reason why I am 
exporting it is that we can reuse it in some places like cpuidle/freq
which deals with raw kobjects directly and can be moved to device 
attributes.

> Skimming over the other patches, you use cpu_device_create() only in
> one place. Why not hard-code this all there? It is totally OK to do
> device initialization in drivers. All the helpers (like
> device_create(), device_create_with_groups(), and so on) are just
> convenience functions. The driver-core API explicitly allows drivers
> to initialize devices manually.
>
> Nevertheless, this patch looks fine.
>

Thanks for having a look at this.

Regards,
Sudeep

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/