Re: [PATCH v3 6/6] mfd: cros_ec: Instantiate sub-devices from device tree

[Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On Thu, 18 Sep 2014, Javier Martinez Canillas wrote:

> Hello Lee,
> 
> On 09/17/2014 06:31 PM, Lee Jones wrote:
> >>  
> >> -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",
> >> -	},
> >> -};
> >> -
> >>  int cros_ec_register(struct cros_ec_device *ec_dev)
> >>  {
> >>  	struct device *dev = ec_dev->dev;
> >> +	struct device_node *node = dev->of_node;
> >>  	int err = 0;
> >>  
> >>  	if (ec_dev->din_size) {
> >> @@ -140,12 +129,12 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
> >>  
> >>  	mutex_init(&ec_dev->lock);
> >>  
> >> -	err = mfd_add_devices(dev, 0, cros_devs,
> >> -			      ARRAY_SIZE(cros_devs),
> >> -			      NULL, ec_dev->irq, NULL);
> >> -	if (err) {
> >> -		dev_err(dev, "failed to add mfd devices\n");
> >> -		return err;
> > 
> > So these devices will only ever probe with DT now ...
> >
> 
> Well, these are preparatory patches to reduce the delta between upstream and
> the downstream so the missing functionality could be added. One of the missing
> drivers is the cros_ec_dev.c [0] which allows user-space to access the
> ChromeOS Embedded Controller using a virtual character device (/dev/cros_ec).
> 
> Since that is a virtual device, it does not fit on the DT which only describes
> hw and also is used on x86 machines so that subdevice is still probed using
> mfd_add_devices() and the mfd_cells array is not empty in the downstream
> cros_ec driver [1].
> 
> That's why I didn't just made the cros_ec MFD to depend on OF, since I didn't
> want to diverge too much from the downstream driver because the idea of the
> series was to reduce the difference in order to add the missing bits on top.
> 
> >> +	if (node) {
> > 
> > So it would be wrong for dev->of_node not to be populated.
> > 
> 
> As explained above, DT, non-DT and x86 platforms instantiate the cros-ec-dev
> cells but DT platforms can define other child nodes. But I can remove the
> conditional if you want and reintroduce it once cros-ec-dev support is added.

Yes, that makes sense.  I only care about doing what's right for
Mainline, so if it doesn't make sense here, then we shouldn't be doing
it.

> >> +		err = of_platform_populate(node, NULL, NULL, dev);
> >> +		if (err) {
> >> +			dev_err(dev, "Failed to register subordinate devices");
> >> +			return err;
> >> +		}
> >>  	}
> >>  
> >>  	dev_info(dev, "Chrome EC device registered\n");
> > 
> 
> Best regards,
> Javier
> 
> [0]:
> https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/drivers/mfd/cros_ec_dev.c
> [1]:
> https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/drivers/mfd/cros_ec.c#93

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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