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Message-ID: <CAL_JsqLWPfi9ynLbkzHkpcSHHg3ciwCcAN1uGcjXhnBAXZ74zw@mail.gmail.com>
Date: Tue, 29 Sep 2015 12:28:11 -0500
From: Rob Herring <robh@...nel.org>
To: Marc Zyngier <marc.zyngier@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Mark Rutland <mark.rutland@....com>,
Rob Herring <robh+dt@...nel.org>,
Jason Cooper <jason@...edaemon.net>,
Thomas Gleixner <tglx@...utronix.de>,
Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 1/4] of: Add of_parse_phandle_with_opt_args() helper function
On Tue, Sep 22, 2015 at 12:52 PM, Marc Zyngier <marc.zyngier@....com> wrote:
> of_parse_phandle_with_args() is slightly inflexible as it doesn't
> allow the (unusual) case where the #*-cells property is not defined.
> In order to support this, introduce of_parse_phandle_with_opt_args()
> which assumes that #*-cells is zero when it is not defined,
zero or cell_count - 1?
I would be okay with always assuming zero rather than being an error
if that simplifies things. It is not really the kernel's job to be a
dtb validator.
Also, I assume this was done for some compatibility? In general, we
should be explicit, so "#msi-cells = <0>" should be recommended and we
should update dts files if they are not.
Rob
> as required by the msi-parent binding
>
> This is done by turning __of_parse_phandle_with_args into an even
> bigger monster, which is a bit frightening.
>
> Acked-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
> drivers/of/base.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
> include/linux/of.h | 3 +++
> 2 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 8b5a187..1612342e 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -1479,6 +1479,10 @@ static int __of_parse_phandle_with_args(const struct device_node *np,
> * (i.e. cells_name not set, but cell_count is set),
> * except when we're going to return the found node
> * below.
> + *
> + * If #*-cells is not found, but cell_count is set
> + * to a non-zero value, use (cell_count-1) as a
> + * fallback value.
> */
> if (cells_name || cur_index == index) {
> node = of_find_node_by_phandle(phandle);
> @@ -1490,13 +1494,21 @@ static int __of_parse_phandle_with_args(const struct device_node *np,
> }
>
> if (cells_name) {
> - if (of_property_read_u32(node, cells_name,
> - &count)) {
> + int ret;
> + ret = of_property_read_u32(node, cells_name,
> + &count);
> + if (ret && !cell_count) {
> pr_err("%s: could not get %s for %s\n",
> np->full_name, cells_name,
> node->full_name);
> goto err;
> }
> + if (ret) {
> + count = cell_count - 1;
> + pr_debug("%s: could not get %s for %s, assuming %d\n",
> + np->full_name, cells_name,
> + node->full_name, count);
> + }
> } else {
> count = cell_count;
> }
> @@ -1628,6 +1640,54 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
> EXPORT_SYMBOL(of_parse_phandle_with_args);
>
> /**
> + * of_parse_phandle_with_opt_args() - Find a node pointed by phandle in a list
> + * @np: pointer to a device tree node containing a list
> + * @list_name: property name that contains a list
> + * @cells_name: property name that specifies phandles' arguments count
> + * @index: index of a phandle to parse out
> + * @out_args: optional pointer to output arguments structure (will be filled)
> + *
> + * This function is useful to parse lists of phandles and their arguments.
> + * If cells_name is not found, then it is assumed to be zero.
> + * Returns 0 on success and fills out_args, on error returns appropriate
> + * errno value.
> + *
> + * Caller is responsible to call of_node_put() on the returned out_args->np
> + * pointer.
> + *
> + * Example:
> + *
> + * phandle1: node1 {
> + * #list-cells = <2>;
> + * }
> + *
> + * phandle2: node2 {
> + * }
> + *
> + * phandle3: node3 {
> + * #list-cells = <1>;
> + * }
> + *
> + * node3 {
> + * list = <&phandle1 1 2 &phandle2 &phandle 3>;
> + * }
> + *
> + * To get a device_node of the `node2' node you may call this:
> + * of_parse_phandle_with_args(node3, "list", "#list-cells", 1, &args);
> + */
> +int of_parse_phandle_with_opt_args(const struct device_node *np,
> + const char *list_name,
> + const char *cells_name, int index,
> + struct of_phandle_args *out_args)
> +{
> + if (index < 0)
> + return -EINVAL;
> + return __of_parse_phandle_with_args(np, list_name, cells_name, 1,
> + index, out_args);
> +}
> +EXPORT_SYMBOL(of_parse_phandle_with_opt_args);
> +
> +/**
> * of_parse_phandle_with_fixed_args() - Find a node pointed by phandle in a list
> * @np: pointer to a device tree node containing a list
> * @list_name: property name that contains a list
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 2194b8c..ae6cd03 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -328,6 +328,9 @@ extern struct device_node *of_parse_phandle(const struct device_node *np,
> extern int of_parse_phandle_with_args(const struct device_node *np,
> const char *list_name, const char *cells_name, int index,
> struct of_phandle_args *out_args);
> +extern int of_parse_phandle_with_opt_args(const struct device_node *np,
> + const char *list_name, const char *cells_name, int index,
> + struct of_phandle_args *out_args);
> extern int of_parse_phandle_with_fixed_args(const struct device_node *np,
> const char *list_name, int cells_count, int index,
> struct of_phandle_args *out_args);
> --
> 2.1.4
>
--
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