linux-kernel - Re: [PATCH v1 2/3] of: Add support for reading a s32 from a multi-value property.

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Message-ID: <23748508.K8gp1eOYRv@diego>
Date:	Tue, 16 Aug 2016 14:09:52 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Finlye Xiao <finley.xiao@...k-chips.com>
Cc:	srinivas.kandagatla@...aro.org, maxime.ripard@...e-electrons.com,
	robh+dt@...nel.org, frowand.list@...il.com, sre@...nel.org,
	dbaryshkov@...il.com, dwmw2@...radead.org, mark.rutland@....com,
	khilman@...nel.org, nm@...com, rjw@...ysocki.net,
	viresh.kumar@...aro.org, sboyd@...eaurora.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	wxt@...k-chips.com, jay.xu@...k-chips.com,
	rocky.hao@...k-chips.com, tim.chen@...k-chips.com,
	tony.xie@...k-chips.com, ulysses.huang@...k-chips.com,
	lin.huang@...k-chips.com
Subject: Re: [PATCH v1 2/3] of: Add support for reading a s32 from a multi-value property.

Hi Finley,

Am Dienstag, 16. August 2016, 10:38:58 schrieb Finlye Xiao:
> From: Finley Xiao <finley.xiao@...k-chips.com>
> 
> This patch adds an of_property_read_s32_index() function to allow
> reading a single indexed s32 value from a property containing multiple
> s32 values.
>
> Signed-off-by: Finley Xiao <finley.xiao@...k-chips.com>

for people reading along, this simply duplicates what of_property_read_s32 
already does, only for indexed properties.

But I do have one issue below.

> ---
>  drivers/of/base.c  | 23 +++++++++++++++++++++++
>  include/linux/of.h | 10 ++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 7792266..346457d 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -1200,6 +1200,29 @@ int of_property_read_u32_index(const struct
> device_node *np, EXPORT_SYMBOL_GPL(of_property_read_u32_index);
> 
>  /**
> + * of_property_read_s32_index - Find and read a s32 from a multi-value
> property. + *
> + * @np:		device node from which the property value is to be read.
> + * @propname:	name of the property to be searched.
> + * @index:	index of the u32 in the list of values
> + * @out_value:	pointer to return value, modified only if no error.
> + *
> + * Search for a property in a device node and read nth 32-bit value from
> + * it. Returns 0 on success, -EINVAL if the property does not exist,
> + * -ENODATA if property does not have a value, and -EOVERFLOW if the
> + * property data isn't large enough.
> + *
> + * The out_value is modified only if a valid s32 value can be decoded.
> + */
> +int of_property_read_s32_index(const struct device_node *np,
> +			       const char *propname, u32 index, s32 *out_value)
> +{
> +	return of_property_read_u32_index(np, propname, index,
> +		(u32 *)out_value);
> +}
> +EXPORT_SYMBOL_GPL(of_property_read_s32_index);

I think this could very well live directly in the of.h header below 
of_property_read_s32 or so.

As this also only calls the more generic u32 variant, it can be just a static 
inline there and does not need to duplicate the whole stub voodoo, as the 
of_property_read_u32_index will also generate the -ENOSYS error in the !OF 
case.


Heiko