linux-kernel - Re: [Qualcomm PM8921 MFD v2 4/6] mfd: pm8xxx-mpp: Add pm8xxx MPP driver

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Date:	Thu, 10 Mar 2011 09:26:38 +0530
From:	Trilok Soni <tsoni@...eaurora.org>
To:	Abhijeet Dharmapurikar <adharmap@...eaurora.org>
CC:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	davidb@...eaurora.org, "David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Daniel Walker <dwalker@...o99.com>,
	David Collins <collinsd@...eaurora.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Joe Perches <joe@...ches.com>,
	Russell King <linux@....linux.org.uk>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Stepan Moskovchenko <stepanm@...eaurora.org>,
	Linus Walleij <linux.walleij@...rricsson.com>,
	Thomas Glexiner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Qualcomm PM8921 MFD v2 4/6] mfd: pm8xxx-mpp: Add pm8xxx MPP
 driver

Hi Abhi,

On 3/10/2011 9:06 AM, Abhijeet Dharmapurikar wrote:
> Mark Brown wrote:
>> On Mon, Mar 07, 2011 at 10:09:48PM -0800, adharmap@...eaurora.org wrote:
>>
>>> +    mpp_chip->gpio_chip.label = PM8XXX_MPP_DEV_NAME;
>>> +    mpp_chip->gpio_chip.direction_input = pm8xxx_mpp_dir_input;
>>> +    mpp_chip->gpio_chip.direction_output = pm8xxx_mpp_dir_output;
>>> +    mpp_chip->gpio_chip.to_irq = pm8xxx_mpp_to_irq;
>>> +    mpp_chip->gpio_chip.get = pm8xxx_mpp_get;
>>> +    mpp_chip->gpio_chip.set = pm8xxx_mpp_set;
>>> +    mpp_chip->gpio_chip.dbg_show = pm8xxx_mpp_dbg_show;
>>> +    mpp_chip->gpio_chip.ngpio = pdata->core_data.nmpps;
>>> +    mpp_chip->gpio_chip.can_sleep = 1;
>>> +    mpp_chip->gpio_chip.dev = &pdev->dev;
>>> +    mpp_chip->gpio_chip.base = pdata->mpp_base;
>>
>> It's seems really odd that you're adding gpiolib stuff here when you've
>> also got a separate gpiolib driver.  Possibly this all shouldn't
>> actually be split up as much as it is - there's also the issue with the
>> gpiolib driver needing to peer into the interrupt controller.  It might
>> simplify the code if things were merged more.
> 
> I dont think merging code will help here. gpio lines and mpp lines are very different piece of hardware,they have a different register map and different config attributes. They do fall under the generic 'gpiolib' umbrella, but it seems clean to keep them separate.
> 
> I agree with you that gpio code needs to call on interrupt controller ( a complicated hardware design) but I think I have a clean software implementation to manage it.
> 

It would be good to add that MPP do have more functionality than normal GPIO. So, I expect that in future
we might have few exported APIs beyond gpiolib integration. 

---Trilok Soni

-- 
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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