linux-kernel - Re: [PATCH 2/2] device property: add description of fwnode cases

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Date:   Thu, 7 Jan 2021 16:11:23 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        andriy.shevchenko@...ux.intel.com, linux-acpi@...r.kernel.org,
        rafael@...nel.org, bard.liao@...el.com
Subject: Re: [PATCH 2/2] device property: add description of fwnode cases

On Tue, Jan 05, 2021 at 05:11:46PM +0800, Bard Liao wrote:
> There are only four valid fwnode cases which are
> - primary --> secondary --> -ENODEV
> - primary --> NULL
> - secondary --> -ENODEV
> - NULL
> 
> dev->fwnode should be converted between the 4 cases above no matter
> how/when set_primary_fwnode() and set_secondary_fwnode() are called.
> Describe it in the code so people will keep it in mind.
> 
> Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/base/core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 51b9545a050b..17eb14607074 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4414,6 +4414,12 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
>   *
>   * Set the device's firmware node pointer to @fwnode, but if a secondary
>   * firmware node of the device is present, preserve it.
> + *
> + * Valid fwnode cases are:
> + *  - primary --> secondary --> -ENODEV
> + *  - primary --> NULL
> + *  - secondary --> -ENODEV
> + *  - NULL
>   */
>  void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>  {
> @@ -4432,6 +4438,7 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>  	} else {
>  		if (fwnode_is_primary(fn)) {
>  			dev->fwnode = fn->secondary;
> +			/* Set fn->secondary = NULL to keep fn as a primary fwnode */
>  			if (!(parent && fn == parent->fwnode))
>  				fn->secondary = NULL;
>  		} else {
> -- 
> 2.17.1

thanks,

-- 
heikki