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Re: [PATCH 1/2]: Add support for Dallas/Maxim DS1685/1687 RTC

To: Lars-Peter Clausen <lars@metafoo.de>
Subject: Re: [PATCH 1/2]: Add support for Dallas/Maxim DS1685/1687 RTC
From: Kumba <kumba@gentoo.org>
Date: Thu, 17 Feb 2011 04:57:02 -0500
Cc: Linux MIPS List <linux-mips@linux-mips.org>, rtc-linux@googlegroups.com
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On 02/16/2011 18:23, Lars-Peter Clausen wrote:

Just pass the error up to rtc core.

How? I looked at a few other drivers, but they, too, call dev_err() or dev_dbg(). Others don't appear to send any kind of string-based error value anywhere, they just return a -E* value.


There is no need for these checks the core takes care that the values are valid.

I've seen a few other RTC drivers implement these checks. It's really hard to tell what drivers are, I guess, "right" and which ones are "wrong" in their approach when you've got already-accepted drivers in the tree doing things that I'm trying to fix in this driver.

That said, how is the core running these checks when I quickly turn around and write the values back to the RTC?


        return rtc_valid_tm(&arlm->time);

Noted -- Probably form when I copied one of the time read functions or such. Alarm support wasn't in the original version of this driver when I found it.


Why has 'enabled' to be a pointer?

No idea to be honest. I think I copied it from another driver. I'll re-review it when I get to that point in fixing things.


resource_size(res) instead of res->end - res->start + 1
and it would be easier to just save the pointer to res instead of saving both
size and start;

Noted, I see a few drivers using this syntax, so I'll adapt to it.


If CONFIG_SYSFS is not defined you'll get an compile error.

Noted, thanks!


Since the irq handler references the rtc device it should be freed before the
rtc device.

Noted, thanks!


There doesn't seem to be any code inside this file which is used outside of
ds1685.c so it might be a good idea to merge the two files, or at least move
this file to drivers/rtc/

I wasn't quite sure where headers typically went. include/linux/rtc already existed, so I thought it was created at some point for holding .h files for RTC drivers. IP32 will need to reference this header down the road anyways. No harm if it has to look into drivers/rtc?


Just use BIT(x) instead of adding these defines

Noted, will research.


I think you should really use readb(pdata->regs + REG) instead of the following
structs. Maybe add a helper function in the form of:
static uint8_t ds1685_read(struct ds1685_priv *ds1685, unsigned int reg) {
        return readb(pdata->regs + REG);
}

That should also help with the different paddings introduced in patch 2.

Working on this now. Ran into some road blocks with gcc and inlining, but I worked around it.


All these macros that follow should really be functions.

Even the large ds1685_begin_data_access macro? I can stick it into a inlined function, but I thought a macro was better. Or am I trying to outfox the compiler by doing so?

If I do inline it, I need a fix for passing errors back to the RTC core. I can't use dev_err() because it needs the device struct to work with, and I want to avoid passing too many arguments to an inlinable function.

Thoughts?  The rest should be easy to convert into inlined functions.


Thanks!,

--
Joshua Kinard
Gentoo/MIPS
kumba@gentoo.org

"The past tempts us, the present confuses us, the future frightens us. And our lives slip away, moment by moment, lost in that vast, terrible in-between."

--Emperor Turhan, Centauri Republic

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