linux-kernel - Re: [PATCH] of: Output devicetree alias names in uevent

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Date:	Wed, 05 Dec 2012 23:03:17 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Stepan Moskovchenko <stepanm@...eaurora.org>
Cc:	Rob Herring <rob.herring@...xeda.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-arm-msm@...r.kernel.org,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Daniel Walker <dwalker@...o99.com>,
	David Brown <davidb@...eaurora.org>, mbohan@...eaurora.org,
	Stepan Moskovchenko <stepanm@...eaurora.org>
Subject: Re: [PATCH] of: Output devicetree alias names in uevent

On Tue,  4 Dec 2012 18:30:37 -0800, Stepan Moskovchenko <stepanm@...eaurora.org> wrote:
> In some situations, userspace may want to resolve a
> device by function and logical number (ie, "serial0")
> rather than by the base address or full device path. Being
> able to resolve a device by alias frees userspace from the
> burden of otherwise having to maintain a mapping between
> device addresses and their logical assignments on each
> platform when multiple instances of the same hardware block
> are present in the system.
> 
> Although the uevent device attribute contains devicetree
> compatible information and the full device path, the uevent
> does not list the alises that may have been defined for the
> device.
> 
> Signed-off-by: Stepan Moskovchenko <stepanm@...eaurora.org>
> ---
> I have followed the OF_COMPATIBLE convention for adding the
> uevent variables for the alias names, but I can follow some
> other convention if people feel something else is more
> appropriate.

No, this seems fine. Comments below.

>  drivers/of/base.c         |   25 +++++++++++++++++++++++++
>  drivers/of/device.c       |    1 +
>  include/linux/of_device.h |    2 ++
>  3 files changed, 28 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 5806449..291f0a0 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -19,6 +19,7 @@
>   */
>  #include <linux/ctype.h>
>  #include <linux/module.h>
> +#include <linux/device.h>
>  #include <linux/of.h>
>  #include <linux/spinlock.h>
>  #include <linux/slab.h>
> @@ -1177,6 +1178,30 @@ static void of_alias_add(struct alias_prop *ap, struct device_node *np,
>  }
> 
>  /**
> + * of_device_uevent_aliases - Display OF alises in uevent
> + */
> +void of_device_uevent_aliases(struct device_node *node,
> +			      struct kobj_uevent_env *env)
> +{
> +	struct alias_prop *app;
> +	int seen = 0;
> +
> +	mutex_lock(&of_aliases_mutex);
> +	list_for_each_entry(app, &aliases_lookup, link) {
> +		if (node == app->np) {
> +			add_uevent_var(env, "OF_ALIAS_%d=%s%d", seen, app->stem,
> +				       app->id);

add_uevent_var(env, "OF_ALIAS_%d=%s", seen, app->alias);

> +			seen++;
> +		}
> +	}
> +
> +	if (seen)
> +		add_uevent_var(env, "OF_ALIAS_N=%d", seen);
> +
> +	mutex_unlock(&of_aliases_mutex);
> +}

Why is this implemented as a separate function? Do you forsee it being
called by something else? If not, then just roll it into the body of
of_device_uevent_aliases() please.

Oh, wait, alias_prop is only defined in drivers/of/base.c. Rats. Can you
create a header named drivers/of/of_private.h to move it into please? I
don't want the uevent stuff to appear in drivers/of/base.c.

> +
> +/**
>   * of_alias_scan - Scan all properties of 'aliases' node
>   *
>   * The function scans all the properties of 'aliases' node and populate
> diff --git a/drivers/of/device.c b/drivers/of/device.c
> index 4c74e4f..06e122d 100644
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -153,6 +153,7 @@ void of_device_uevent(struct device *dev, struct kobj_uevent_env *env)
>  		seen++;
>  	}
>  	add_uevent_var(env, "OF_COMPATIBLE_N=%d", seen);
> +	of_device_uevent_aliases(dev->of_node, env);
>  }
> 
>  int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env)
> diff --git a/include/linux/of_device.h b/include/linux/of_device.h
> index 901b743..748056d 100644
> --- a/include/linux/of_device.h
> +++ b/include/linux/of_device.h
> @@ -36,6 +36,8 @@ extern ssize_t of_device_get_modalias(struct device *dev,
>  					char *str, ssize_t len);
> 
>  extern void of_device_uevent(struct device *dev, struct kobj_uevent_env *env);
> +extern void of_device_uevent_aliases(struct device_node *node,
> +					struct kobj_uevent_env *env);
>  extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env);
> 
>  static inline void of_device_node_put(struct device *dev)
> --
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
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