linux-kernel - Re: [PATCH v2 1/2] power: Charger-Manager: add initial Charger-Manager driver

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Date:	Tue, 27 Dec 2011 17:05:38 +0900
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Donggeun Kim <dg77.kim@...sung.com>, linux-pm@...r.kernel.org,
	len.brown@...el.com, pavel@....cz, rdunlap@...otime.net,
	cbouatmailru@...il.com, pali.rohar@...il.com, prakity@...vell.com,
	broonie@...nsource.wolfsonmicro.com, lars@...afoo.de,
	kyungmin.park@...sung.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] power: Charger-Manager: add initial
 Charger-Manager driver

2011/12/27 Rafael J. Wysocki <rjw@...k.pl>:
> That should be called rtc_name and I'm not sure if using the name here is
> very convenient.  Perhaps it's better if the caller is responsible for
> opening the RTC device.

Hi Rafael,

Because struct rtc_device is created at rtc_device_register() call of
rtc device driver, the caller (rtc drivers are not supposed to create
charger manager) needs to call rtc_class_open(rtc_name) in order to
feed struct rtc_device to charger manager. Thus, I think that
enforcing the caller to provide struct rtc_device has no significant
benefit. Besides, it would prohibit statically defining struct
charger_global_desc: cannot define struct charger_global_desc example
= { .rtc_device = rtc_class_open("blahblah") };

>> +#define      CM_JIFFIES_SMALL        (2)
>
> Why do you want to use jiffies instead of ktime?
>

It is based on work schedule, which is based on jiffies. If we define
the "small time" with ktime, it should be translated to jiffies
anyway.

>> +static int charger_manager_probe(struct platform_device *pdev)
>> +{
>> +     struct charger_desc *desc = dev_get_platdata(&pdev->dev);
[]
>> +     if (!desc) {
>> +             dev_err(&pdev->dev, "No platform data (desc) found.\n");
>> +             ret = -ENODEV;
>> +             goto err_alloc;
>> +     }
>
> Is there any way to detect whether dev_get_platdata(&pdev->dev) really points
> to an instance of struct charger_desc ?

We are verifying the member values (whether they are in the proper
ranges) later in this probe function.
Other than that, I don't know a method to detect whether this pointer
is really pointing to struct charger_desc except for simply checking
whether it is NULL or not or enforcing users to add some magic values
in the struct to check (like mutex debug mode).

>> +     /* Basic Values. Unspecified are Null or 0 */
>> +     cm->dev = &pdev->dev;
>> +     cm->desc = desc;

We will let cm->desc to alloc some space and copy contents of desc
into cm->desc because desc may be __initdata.

Donggeun will update and submit patchset v3 mostly based on your
valueable comments.

Thank you so much, Rafael.

Cheers! And happy new year!
MyungJoo

-- 
MyungJoo Ham, Ph.D.
Mobile Software Platform Lab, DMC Business, Samsung Electronics
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