linux-kernel - Re: [PATCH v2 03/10] mfd: cros_ec: Instantiate sub-devices from device tree

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Date:	Wed, 13 May 2015 13:10:35 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	Bill Richardson <wfrichar@...omium.org>,
	Simon Glass <sjg@...gle.com>,
	Gwendal Grignou <gwendal@...gle.com>,
	Stephen Barber <smbarber@...omium.org>,
	Filipe Brandenburger <filbranden@...gle.com>,
	Todd Broch <tbroch@...omium.org>,
	Alexandru M Stan <amstan@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/10] mfd: cros_ec: Instantiate sub-devices from
 device tree

On Wed, 13 May 2015, Javier Martinez Canillas wrote:

> Hello Lee,
> 
> On 05/13/2015 01:32 PM, Lee Jones wrote:
> > On Sat, 09 May 2015, Javier Martinez Canillas wrote:
> > 
> >> From: Todd Broch <tbroch@...omium.org>
> >> 
> >> If the EC device tree node has sub-nodes, try to instantiate them as
> >> MFD sub-devices.  We can configure the EC features provided by the board.
> >> 
> >> Signed-off-by: Todd Broch <tbroch@...omium.org>
> >> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> >> Tested-by: Heiko Stuebner <heiko@...ech.de>
> >> Reviewed-by: Gwendal Grignou <gwendal@...omium.org>
> >> Tested-by: Gwendal Grignou <gwendal@...omium.org>
> >> ---
> >> 
> >> Changes since v1:
> >>   - Added Heiko Stuebner and Gwendal Grignou Tested-by tag
> >>   - Added Gwendal Grignou Reviewed-by tag
> >>   - Use automatic device ID instead of 1 as suggested by Lee Jones
> >>   - Remove #ifdeffery and check for of_node to register sub-devices
> >>     Suggested by Lee Jones
> >> ---
> >>  drivers/mfd/cros_ec.c | 22 +++++++++++-----------
> >>  1 file changed, 11 insertions(+), 11 deletions(-)
> >> 
> >> diff --git a/drivers/mfd/cros_ec.c b/drivers/mfd/cros_ec.c
> >> index c4aecc6f8373..1574a9352a6d 100644
> >> --- a/drivers/mfd/cros_ec.c
> >> +++ b/drivers/mfd/cros_ec.c
> >> @@ -17,6 +17,7 @@
> >>   * battery charging and regulator control, firmware update.
> >>   */
> >>  
> >> +#include <linux/of_platform.h>
> >>  #include <linux/interrupt.h>
> >>  #include <linux/slab.h>
> >>  #include <linux/module.h>
> >> @@ -109,18 +110,8 @@ EXPORT_SYMBOL(cros_ec_cmd_xfer);
> >>  
> >>  static const struct mfd_cell cros_devs[] = {
> >>  	{
> >> -		.name = "cros-ec-keyb",
> >> -		.id = 1,
> >> -		.of_compatible = "google,cros-ec-keyb",
> >> -	},
> >> -	{
> >> -		.name = "cros-ec-i2c-tunnel",
> >> -		.id = 2,
> >> -		.of_compatible = "google,cros-ec-i2c-tunnel",
> >> -	},
> >> -	{
> >>  		.name = "cros-ec-ctl",
> >> -		.id = 3,
> >> +		.id = PLATFORM_DEVID_AUTO,
> >>  	},
> >>  };
> >>  
> >> @@ -150,6 +141,15 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
> >>  		return err;
> >>  	}
> >>  
> >> +	if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
> > 
> > You don't need to check for OF.  of_node will be NULL if OF isn't
> > enabled.
> >
> 
> Yes, you don't need it but IS_ENABLED(CONFIG_OF) causes the check to be
> optimized away by the compiler if CONFIG_OF is not enabled AFAIK.
> 
> Without the IS_ENABLED(CONFIG_OF) check, this becomes a pointless pointer
> check that will always evaluate to false on systems without CONFIG_OF
> since as you said of_node will be present when CONFIG_OF is not enabled.
> But the compiler has no way to know it will always be NULL to optimize it
> away AFAICT.

Yes, you're absolutely right.  You passed the test. ;)

Acked-by: Lee Jones <lee.jones@...aro.org>

> >> +		err = of_platform_populate(dev->of_node, NULL, NULL, dev);
> >> +		if (err) {
> >> +			mfd_remove_devices(dev);
> >> +			dev_err(dev, "Failed to register sub-devices\n");
> >> +			return err;
> >> +		}
> >> +	}
> >> +
> >>  	dev_info(dev, "Chrome EC device registered\n");
> >>  
> >>  	return 0;

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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