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: Fri, 02 Dec 2011 08:55:41 -0700 [thread overview]
Message-ID: <4ED8F4FD.4030002@nvidia.com> (raw)
In-Reply-To: <CAPnjgZ29tsNXd1+1eXdTHRjgh_MQJrXoc23_oqO9UPJ73mu7ZA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On 12/01/2011 06:01 PM, Simon Glass wrote:
> Hi Stephen,
>
> On Mon, Nov 28, 2011 at 10:41 AM, Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> wrote:
>> 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>
>>> +/**
>>> + * 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?
>
> Which bool type? It is returning an int.
I was asking if the return type could be changed to bool.
>>> +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.
>
> It is useful to be able to set the value to 0 or 1 (with fdtget/put),
> rather than remove or add the property. A value with a length of less
> than one cell is considered illegal here.
>
> The basic idea is that the presence of the property means that it is
> 'true'. If it happens to have a value, then we allow that to specify
> 'false' if it is zero.
Well, it's more up to standard device tree practice, not me. I've
certainly sent patches that used a property with 0/1 value as a bool
and received review feedback from DT experts that DT represents bools
as present/absent properties, both with no value, so I assume zero
length.
--
nvpublic
next prev parent reply other threads:[~2011-12-02 15:55 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
[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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4ED8F4FD.4030002@nvidia.com \
--to=swarren-ddmlm1+adcrqt0dzr+alfa@public.gmane.org \
--cc=TWarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org \
--cc=albert.u.boot-LhW3hqR2+23R7s880joybQ@public.gmane.org \
--cc=devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org \
--cc=sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org \
--cc=u-boot-0aAXYlwwYIKGBzrmiIFOJg@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).