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From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
To: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Cc: U-Boot Mailing List
	<u-boot-0aAXYlwwYIKGBzrmiIFOJg@public.gmane.org>,
	Devicetree Discuss
	<devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>,
	Tom Warren <TWarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Albert ARIBAUD
	<albert.u.boot-LhW3hqR2+23R7s880joybQ@public.gmane.org>
Subject: Re: [PATCH 02/14] fdt: Add functions to access phandles, arrays and bools
Date: Mon, 28 Nov 2011 11:41:32 -0700	[thread overview]
Message-ID: <4ED3D5DC.10502@nvidia.com> (raw)
In-Reply-To: <1322106896-23054-3-git-send-email-sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

On 11/23/2011 08:54 PM, Simon Glass wrote:
> Add a function to lookup a property which is a phandle in a node, and
> another to read a fixed-length integer array from an fdt property.
> Also add a function to read boolean properties.
> 
> Signed-off-by: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

Looking at the U-Boot custodians web page, you need to send the core DT
changes (well, probably anything DT related) to Jerry Van Baren.

> +/**
> + * Look up a property in a node and return its contents in an integer
> + * array of given length. The property must have at least enough data for
> + * the array (4*count bytes). It may have more, but this will be ignored.
> + *
> + * @param blob		FDT blob
> + * @param node		node to examine
> + * @param prop_name	name of property to find
> + * @param array		array to fill with data
> + * @param count		number of array elements
> + * @return 0 if ok, or -FDT_ERR_NOTFOUND if the property is not found,
> + *		or -FDT_ERR_BADLAYOUT if not enough data
> + */
> +int fdtdec_get_int_array(const void *blob, int node, const char *prop_name,
> +		int *array, int count);

The kernel's equivalent of this function retrieves an array of U32s. Is
one version more correct than the other?

> +/**
> + * Look up a boolean property in a node and return it.
> + *
> + * A boolean properly is true if present in the device tree and false if not
> + * present, or present with a 0 value.
> + *
> + * @param blob	FDT blob
> + * @param node	node to examine
> + * @param prop_name	name of property to find
> + * @return 1 if the properly is present; 0 if it isn't present or is 0
> + */
> +int fdtdec_get_bool(const void *blob, int node, const char *prop_name);

Does U-Boot allow use of the "bool" type here?


> +/**
> + * Look up a property in a node and check that it has a minimum length.
> + *
> + * @param blob		FDT blob
> + * @param node		node to examine
> + * @param prop_name	name of property to find
> + * @param min_len	minimum property length in bytes
> + * @param err		0 if ok, or -FDT_ERR_NOTFOUND if the property is not
> +			found, or -FDT_ERR_BADLAYOUT if not enough data
> + * @return pointer to cell, which is only valid if err == 0
> + */
> +static const void *get_prop_len(const void *blob, int node,
> +		const char *prop_name, int min_len, int *err)

Based on the function name, I'd expect it to return the length of the
property; perhaps get_prop_check_min_len?

> +/**
> + * Look up a boolean property in a node and return it.
> + *
> + * A boolean properly is true if present in the device tree and false if not
> + * present, or present with a 0 value.
> + *
> + * @param blob	FDT blob
> + * @param node	node to examine
> + * @param prop_name	name of property to find
> + * @return 1 if the properly is present; 0 if it isn't present or is 0
> + */
> +int fdtdec_get_bool(const void *blob, int node, const char *prop_name)
> +{
> +	const s32 *cell;
> +	int len;
> +
> +	debug("%s: %s\n", __func__, prop_name);
> +	cell = fdt_getprop(blob, node, prop_name, &len);
> +	if (!cell)
> +		return 0;
> +	if (len >= sizeof(u32) && *cell == 0)
> +		return 0;
> +
> +	return 1;
> +}

In the kernel, I believe that property existence is all that's usually
checked. Is that wrong? Did the definition of a boolean property's value
in the function description above come from the specification? If a
property had a length of 0/1/2/3 with a zero value, it seems very odd to
treat that as true.

-- 
nvpublic

  parent reply	other threads:[~2011-11-28 18:41 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-11-24  3:54 [PATCH 01/14] fdt: Tidy up a few fdtdec problems Simon Glass
2011-11-24  3:54 ` [PATCH 03/14] arm: fdt: Ensure that an embedded fdt is word-aligned Simon Glass
2011-11-24  3:54 ` [PATCH 06/14] tegra: fdt: Add device tree file for Tegra2 Seaboard Simon Glass
     [not found] ` <1322106896-23054-2-git-send-email-sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2011-11-24  3:54   ` [PATCH 02/14] fdt: Add functions to access phandles, arrays and bools Simon Glass
     [not found]     ` <1322106896-23054-3-git-send-email-sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2011-11-28 18:41       ` Stephen Warren [this message]
     [not found]         ` <4ED3D5DC.10502-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2011-11-29  5:12           ` David Gibson
2011-12-02  1:01         ` Simon Glass
     [not found]           ` <CAPnjgZ29tsNXd1+1eXdTHRjgh_MQJrXoc23_oqO9UPJ73mu7ZA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-12-02 15:55             ` Stephen Warren
2011-12-02 16:38               ` Simon Glass
2011-12-02  3:33         ` Jerry Van Baren
2011-12-02  4:58           ` Simon Glass
2011-12-02 17:22             ` Jerry Van Baren
2011-12-02 18:12               ` Simon Glass
2011-11-24  3:54   ` [PATCH 04/14] arm: fdt: Add skeleton device tree file Simon Glass
2011-11-24  3:54   ` [PATCH 05/14] tegra: fdt: Add Tegra2x " Simon Glass
     [not found]     ` <1322106896-23054-6-git-send-email-sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2011-11-28 18:56       ` Stephen Warren
2011-12-02  1:24         ` Simon Glass
     [not found]           ` <CAPnjgZ11cFm15E9MHXno_YGp0NxdOHhGBavYbQBP5Nu_TOtx7A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-12-02 15:58             ` Stephen Warren
2011-12-02 16:47               ` Simon Glass
2011-11-24  3:54   ` [PATCH 07/14] tegra: fdt: Add initial device tree definitions for USB ports Simon Glass
2011-11-24  3:54   ` [PATCH 14/14] tegra: fdt: Enable FDT support for Seaboard Simon Glass
2011-11-28 18:33   ` [PATCH 01/14] fdt: Tidy up a few fdtdec problems Stephen Warren
     [not found]     ` <4ED3D3F2.8070302-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2011-11-29  1:10       ` David Gibson
2011-12-01 20:59     ` Simon Glass
     [not found] ` <1322106896-23054-11-git-send-email-sjg@chromium.org>
     [not found]   ` <4ED3DF1D.6080009@nvidia.com>
     [not found]     ` <CAPnjgZ1-yxq-O-vsy1gNJ8AOzh7Sz9j5PG9Tx1sKpnAxhApJAQ@mail.gmail.com>
     [not found]       ` <4EDD38AC.30908@nvidia.com>
     [not found]         ` <CAPnjgZ0MTaPa4pq1VXk_XbmuDyWTfy-H33W4deNVn2ALUrcW_A@mail.gmail.com>
     [not found]           ` <4EDD429E.8010507@nvidia.com>
     [not found]             ` <CAPnjgZ2G220G-i3PPtS4XJYY0ornWFOoK3=b93jG-6GE_g2O5w@mail.gmail.com>
     [not found]               ` <4EDD5F1B.5060205@nvidia.com>
     [not found]                 ` <CAPnjgZ2h7F228q=pXuf7M9vTASurY3R5an_QV-mrETLf8nzA1A@mail.gmail.com>
     [not found]                   ` <4EDE7E1C.2090203@nvidia.com>
     [not found]                     ` <CAPnjgZ1G+mv6uv8SrdMm7DoqFjeeyVHYv6nbQxn9qixfbQMGvA@mail.gmail.com>
     [not found]                       ` <CAPnjgZ1G+mv6uv8SrdMm7DoqFjeeyVHYv6nbQxn9qixfbQMGvA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-12-07 23:46                         ` [PATCH 10/14] tegra: usb: Add support for USB peripheral Stephen Warren
2011-12-08 21:24                           ` Simon Glass
     [not found]                             ` <CAPnjgZ0AuBNkYKN0JHQyc7DdzwUSZivR+Dv2BkiFsKQBNMeP8A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-12-12 18:18                               ` Stephen Warren
2011-12-12 18:42                                 ` Simon Glass

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